Disclaimer: there are many USB power banks on sale however most of them do not declare the maximum output current and therefore you cannot be sure that it will work in all situations I describe. The equipment I use does work and is proven by my daily experience, the suggestions are not prescriptive but if you choose your own parts you do do at your own risk
It has been some time since my post on chargers and recharge facilities. During the pandemic I have done a considerable amount of land based photography including wildlife, landscape and astrophotography so I have had the opportunity to develop the concept of portability further on the field. So I wanted to share my experience with you all as some of the findings are beneficial in every day situation.
Charging your camera battery
Today some cameras can charge the battery in camera using USB. In almost all cases the camera needs to be turned off to allow charging, as a complete recharge of your battery can take a few hours I never use this method. I always rely on spare batteries typically 3 and a dual battery charger that can be powered using USB. I use Newmova they are cheap and cheerful for both my Panasonic and Olympus cameras.
Newmowa Dual USB Charger for Olympus BLH-1 and OM-D EM1 Mark II, OM-D E-M1X Camera £9.99
Newmowa Dual USB Charger for Panasonic DMW-BLF19 and Panasonic DMC-GH3,DMC-GH4 DMC-GH5, DC-GH5S(DMW-BLF19 Dual USB Charger) £9.99
With 3 batteries you can have two in the charger if needed and one in the camera which means uninterrupted shooting for a long period of time depending on your use.
I also use battery grips in particular for my Olympus camera. Battery grip provide the most benefit when you are not wanting to interrupt shooting while swapping batteries. I usually set the camera to use the grip battery first and the camera as back up which means you can then insert another battery in the grip and keep shooting. I do not recommend using a battery grip as a sole source of power as at the end you can can go through 2 batteries relatively fast if you use quick burst shooting. The other dis-benefit of the grip is the one battery is always locked inside the camera so you need to increase your total battery stock to 4 if you use a dual charger. The grip is very useful to shoot verticals and provide weather sealing but overall is not my favourite option and I only use it for specific session on my Olympus camera because I only have 2 batteries.
There are some working 3rd party battery grip like this one that function AS LONG AS YOU USE ORIGINAL OEM BATTERIES.
Neewer Battery Grip Compatible with Panasonic Lumix G9 Camera Replacement for DMW-BGG9 with Shutter Release Focus Point Control Joystick £59.99
I have not seen versions for Olympus camera and the original battery grip is expensive. I got mine second hand for a good price.
Again if you only have two batteries or you want to rotate 4 batteries a battery grip is a good option if you don’t mind the extra weight.
I use a relatively simple USB power bank as I do not have PD capable cameras. This power bank has a decent capacity but more importantly it can output 4.5A using two outlets.
This power bank has also a light included very useful for your night photography. You can also use it to charge your phone but with two outlets means you can power two dual USB chargers and effectively charge 4 batteries twice until it runs out (typical battery less than 2000 mAh).
This power bank can also be used as constant power supply for cameras that take a dummy battery and do not support powering through USB.
DMW-DCC12 USB Power Cable kit DMW-DCC12 DC Coupler Dmw-Blf19 Dummy Battery (BLF-19 Battery Replacement) Compatible with PANASONIC DMC-GH3 DMC-GH4 DMC-GH3K DMC-GH4K DC-GH5 GH9 and more Digital Cameras £22.99
Using the power bank with this fake battery kit means I can run my GH5 in video for days (8.72x batteries equivalent charge).
IT IS VERY IMPORTANT THAT YOUR POWER BANK OUTPUTS MORE THAN 3A OTHERWISE IF YOU USE MECHANICAL SHUTTER THE CAMERA MAY GO IN SHUTTER VIBRATION AND SUFFER PERMANENT DAMAGE
Some well know power bank from respectable brands like anker and even rawpower themselves only outputs 3A current total so when the mechanical shutter is used and the camera draws more current you run into issue. This also happens when you set a custom white balance and the camera triggers the mechanical shutter. So if you have such power bank you are limited and hence I do not recommend them.
If you also use flash you can use the same chargers I already linked in the previous article
Prices have dropped to £7.99 for the micro USB and £9.99 for the dual USB C and micro USB input. Note that despite the misleading description the two chargers are identical except one has micro USB and the other also USB-C. The USB-C version is slightly bigger (70x90x23 mm USB version vs 97x114x34mm USB C). The USB C version has a stronger output for AAA batteries that I do not use and it does not charge faster standard AA so don’t be mislead.
Another useful accessory if you do astrophotography in humid or cold environment is a lens warmer. There are two versions I recommend the one with the temperature regulator as the strip gets to 50 C and this can increase dark current noise in your shots.
COOWOO Lens Heater Warmer Dew Heater with Temperature Regulator Strip for Ice Fog Universal Camera Telescopic Bottle Heating (Black)
Amazon.com links for my American followers
EBL 40Min Smart Fast USB Battery Charger for AA AAA Ni-MH Rechargeable Batteries
DMW-DCC12 USB Power Cable kit DMW-DCC12 DC Coupler Dmw-Blf19 Dummy Battery (BLF-19 Battery Replacement) Compatible with PANASONIC DMC-GH3 DMC-GH4 DMC-GH3K DMC-GH4K DC-GH5 GH9 and more Digital Cameras
Neewer Battery Grip for Panasonic G9
RavPower 16750 mAh 4.5A dual USB power bank
NewMowa Olympus dual charger
NewMowa Panasonic dual USB charger
COOWOO Lens Heater Warmer Dew Heater with Temperature Regulator Strip for Ice Fog Universal Camera Telescopic Bottle Heating (Black)
The previous post on the technical nature of V-LOG has stirred up quite a bit of unset among those people that advocate the use of it as a preferred gamma for video capture. In this post I will show some data point to help you make an informed decision based on what you are planning to shoot in your video project.
Basics of Display Gamma and Dynamic Range
First of all a bit of background on gamma curves. The standard video gamma is based on a correction factor of 0.45 as screen decode it with the reciprocal value 2.22.
Cinema gamma is historically based on a value of 1/2.6 as projectors decode with a gamma of 2.6.
Today most of our content is consumed on phones, monitors or Tv screens as well as of course cinemas but for the purpose of this post I will assume we do not have a real ambition to project in cinemas.
To give some ideas of the dynamic range of the display consider those values
Tv (1886 HDTV)
Typical Display Dynamic Range
It is important to understand how the content we produce will be consumed when we capture our source material as otherwise our video pipeline may be suboptimal.
Mobile phones and tablets are now the predominant platform to consume content and looking at the table above this means that in terms of dynamic range there is not a high requirement. In addition phones and computer monitors may also not be particularly accurate in terms of colour rendition.
HDR content, due to lack of widespread compatibility, is growing on mobile phones but remains a product for high end platforms such as HDR TVs and Projectors.
It follows that content that will be displayed at the best quality on the most common platforms has pretty limited requirements in terms of dynamic range and other qualities are perhaps more important such as sharpness, low amount of noise, colour rendition and delivery of what looks high contrast on a limited contrast medium.
A further obvious consideration is that standard rec709/sRGB video is limited to 10 stops of dynamic range in the display (contrast ratio 1000:1) while new TV sets aligned to BT.1886 can display 11 stops )(Contrast ratio 2000:1). So no matter how you acquire if you end up in rec709 the dynamic range is limited and it becomes more important to accurately capture tones and colors.
Gamma Curves for Capture
As explained capture gamma is the reciprocal of display gamma and therefore majority of cameras capture a standard video gamma (0.45) or in some cases an HDR gamma (logarithmic). I do not want this post to become a deep dive on HDR video of which I have written enough however to stay on course I want to compare traditional gamma (non linear) and log gamma.
In the following graph you see the bit codes output vs input of a standard video gamma (1/2.2) a cine gamma (1/2.6) and a log gamma (v-log).
In broad terms you can see that a video gamma produces an output of 3865 vs 16383 bits, a cinema gamma sets at 3166, while a Log gamma can take all 14 bits of data and still be within bit value 960.
It follows that to store the whole set of values read at 14 bits into a 10 bits container a standard gamma needs to do some scaling while a log gamma does not need scaling to fit into a 10 bits container. This also explains why exposure values in log are 2 stops higher than standard video for a 14 bit range, while for a 12 bit range the offset is one stop. As the meter is using a standard RGB gamma all values are rescaled back.
You notice that at no point here I have made references to dynamic range. The camera dynamic range is solely related to the maximum well capacity vs the read noise and it does not relate to the gamma curve being used, however the different compression of the gamma curve have an effect on how tones are mapped and on the perceived dynamic range.
Camera Dynamic Range vs Display Dynamic Range
The overall camera dynamic range influences what you can do with your content and if it is worthwhile to produce an HDR version or not.
If we compare the previous table of display dynamic range vs camera dynamic range and we focus on nominal values (SNR=1) and photographic (SNR=20) we can see what device we need for our purpose.
Dynamic Range by Sensor Type
We can see that if all we need to do is to output on a mobile device or a computer monitor smaller sensor are adequate, however for HDR production larger format are preferred. Obviously we can stretch SNR to lower values and this will upgrade the above table of 1 stops or so but not change our reasoning substantially.
Gamma curves vs Bit codes mapping
The various gamma curves have a different distribution of tones (bit values), in this table I compare a video gamma vs cinema a reduced 12 stops log and a full Vlog for a full frame sensor camera.
For the purpose of this comparison blacks are bit codes in the lowest 10%, Shadows are up to 18%, midtones up to 75%, highlights up to 90% and whites above. Blacks and whites do not have color information but just brightness while shadows, midtones and highlights contain respectively dark, medium and light hues.
A standard video gamma has over 45% of midtones, those are the colors and tones with intermediate values so produce softer tones. Shadows are just above 35% with highlights under 10% and blacks and whites around 5%.
If we look at a cinema gamma we can see that shadows are now predominant and very close to the midtones, highlights, whites and blacks are compressed.
V-LogL (12 stops DR 12 bit implementation) has the largest range in shadows, midtones are compressed around 50% compared to a video gamma, blacks are subtantially more than a video gamma, and while highlights are compressed, whites are super whites are greatly expanded.
Full VLog is dominated by whites that make 38% of the bit values, Shadows are at 32% with midtones now under 20% and highlights compressed. Blacks remain expanded.
Choosing a Gamma Curve for your Video Project
Our decision tree starts from the content which determines the device we need. Once we have a device capable of a given dynamic range we can make appropriate choices in terms of gamma curve.
Broadly speaking compact cameras and micro four thirds do not have enough device dynamic range at sufficient level of SNR to justify a high dynamic range gamma. There are some very specific exception where this may be worth it (Panasonic GH5s) but in general terms a standard MFT camera for photography should be limited to video or cinema gamma for optimal results as the dynamic range is limited and compression is not required.
If you own an MFT camera your choice is between a video gamma and a cinema gamma. Depending on the look you want to achieve you may choose one or the other. Video gamma has generally more contrast (more blacks and highlights and whites) while Cine gamma has a balance between midtones and shadows but not strong blacks and whites giving overall a softer look.
If you own a full frame or apsc camera you have more options which means you need to think more about the gamma curve to be used. HDR content requires a log curve you can then decide to use a cinema or video gamma if you do not want to output HDR or want to achieve a different look. It is important to note that log gamma have lots of bit values in whites and super whites and those do not exist in many typical scenes.
Scene vs Dynamic Range
While the current effort of camera manufacturers is to promote high dynamic range the reality is that in most cinematography situation you use devices that reduce contrast and therefore dynamic range (think about pro mist filters).
The DR of a scene can be evaluated looking at the histogram. This is of course influenced by the gamma curve so it is important to do this evaluation taking a photograph not video.
The following are example of scenes with the underlying histogram.
It may be useful to see the effect of LOG using the LUTs in photoshop on the raw data
The example above shows that a significant number of midtones have been lost in the conversion with no DR benefit as the scene essentially lacked it.
For underwater video purposes as the water reduces contrast and smooths highlights I would not recommend shooting log or HDR with the exception of very specific scenarios. Likewise if I am shooting a v(ideo)log or an interview there is no requirement for extra dynamic range and log compression is not required.
Outdoor scenes especially in bright conditions, snow, are appropriate for HDR and should be shot with a log format assuming of course the luminance of the scene is not being reduced with ND filters or similar.
Events like weddings can have challenging conditions with a mix of low contrast indoor and bright outdoors with the bride typically dressed in white so in effect those can be very demanding on the equipment but you need to bear in mind that if your delivery format is just HD video the benefit of log gamma are greatly reduced and extensive work may be required to bring colours back in check, always account for the limitations of your equipment as well.
There is no doubt that LOG formats in digital cameras have a halo of mystery around them mostly due to the lack of technical documentation on how they really work. In this short article I will explain how the Panasonic V-Log actually works on different cameras. Some of what you will read may be a surprise to you so I have provided the testing methods and the evidence so you can understand if LOG is something worth considering for you or not. I will aim at making this write up self-contained so you have all the information you need here without having to go and search elsewhere, it is not entirely possible to create a layman version of what is after all a technical subject.
A logarithmic operator is a non-linear function that processes the input signal and maps it to a different output value according to a formula. This is well documented in Panasonic V-Log/V-Gamut technical specifications. If you consider the input reflection (in) you can see how the output is related to the input using two formulas:
IRE = 5.6*in+0.125 (in < cut1 ) *
IRE = c*log10(in+b)+d (in >= cut1 )
Where cut1 = 0.01, b=0.00873, c=0.241514, d=0.598206
There are few implications of this formula that are important:
0 input reflectance is mapped to 7.3% IRE
Dark values are not compressed until IRE=18%
Middle Grey (18% reflectance) is still 42% IRE as standard Rec709
White (90% reflectance) is 61% IRE so much lower than Rec709
100% IRE needs input reflectance 4609 which is 5.5 stops headroom for overexposure.
So what we have here is a shift of the black level from 0% to 7.3% and a compression of all tones over 18% this gives the washout look to V-LOG that is mistakenly interpreted as flat but it is not flat at all. In fact the master pedestal as it is known in video or black level is shifted. Another consequence of this formula is that VLOG under 18% IRE works exactly like standard gamma corrected Rec709 so it should have exactly the same performance in the darks with a range between 7.3% and 18% instead of 0-18%.
In terms of ISO measured at 18% reflectante V-LOG should have identical ISO value to any other photo style in your camera this means at given aperture and exposure time the ISO in a standard mode must match V-LOG.
When we look at the reality of V-LOG we can see that Panasonic sets 0 at a value of 50% IRE so generally ⅔ to 1 full stop overexposed this becomes obvious when you look at the waveform. As a result blacks are actually at 10% IRE and whites at 80% once a conversion LUT is applied.
Challenges of Log implementation
LOG conversion is an excellent method to compress a high dynamic range into a smaller bit depth format. The claim is that you can pack the full sensor dynamic range into 10 bits video. Panasonic made this claim for the GH5s and for the S1H, S5.
There is however a fundamental issue. In a consumer digital camera the sensor is already equipped with a digital to analog converter on board and this operates in a linear non log mode. This means the sensor dynamic range is limited to the bit depth of the analog to digital converter and in most cases sensors do not even saturate the on board ADC. It is true that ADC can also resolve portions of bits however this does not largely change the picture.
If we look at the sensor used in the S1H, S5 this is based on a Sony IMX410 that has saturation value of 15105 bits or 13.88 stops of dynamic range. The sensor of the GH5s which is a variant of Sony IMX299 has a saturation of 3895 (at 12 bits) or 11.93 stops.
None of the S1H, S5 or GH5s actually reaches the nominal dynamic range that the ADC can provide at sensor level. The sensor used by the GH5 has more than 12 stops dynamic range and achieves 12.3 EV of engineering DR, as the camera has 12 bits ADC it will resolve an inferior number of tones.
So the starting point is 12 or 14 stops of data to be digitally and not analogically compressed into 10 bits coding. Rec709 has a contrast ratio requirement of 1000:1 which is less than 10 stops dynamic range. This has not to be confused with bit depth. With 8 bits depth you can manage 10 stops using gamma compression. If you finish your work in Rec709 the dynamic range will never exceed log2(1000)=9.97 stops. So when you read that rec709 only has 6.5 stops of DR or similar it is flawed as gamma compression squeezes the dynamic range into a smaller bit depth.
When we look at a sensor with almost 14 stops of dynamic range the standard rec709 gamma compression is insufficient to preserve the full dynamic range as it is by default limited to 10 stops. It follows that logically LOG is better suited to larger sensors and this is where it is widely used by all cinema camera manufacturers.
In practical terms the actual photographic dynamic range (this is defined as the dynamic range you would see on a print of 10″ on the long side at arm length), the one you can see with your eyes in an image, is less than the engineering value. The Panasonic S5 in recent tests showed around 11.5 stops while the GH5S is around 10 and the GH5 9.5 stops of dynamic range. Clearly when you look at a step chart the tool will show more than this value but practically you will not see more DR in real terms.
This means that it is possible that a standard gamma encoded video in 10 bits can be adequate in most situations and nothing more is required. There is also a further issue with noise that the log compression and decompression produces. As any conversion that is not lossless the amount of noise increases: this is especially apparent in the shadows. In a recent test performed with a S5 in low light and measured using neat-video assessment V-Log was one of the worst performed in terms of SNR. The test involved shooting a color checker at 67 lux of ambient illumination and reading noise level on the 4 shadows and darks chips. Though this test was carried out at default setting it has to be noted that even increasing the noise reduction in V-LOG does not eliminate the noise in the shadow as this depends on how V-LOG is implemented.
The actual V-Log implementation
How does V-LOG really work? From my analysis I have found that V-Log is not implemented equally across cameras, this is for sure a dependency on the sensor performance and construction. I do not know how a Varicam camera is built but in order to perform the V-Log as described in the document you need a log converter before the signal is converted to digital. In a digital camera the sensor already has an on board ADC (analog to digital converter) and therefore the output is always linear on a bit scale of 12 or 14 bits. This is a fundamental difference and means that the math as illustrated by Panasonic in the V-LOG/V-Gamut documentation cannot actually be implemented in a consumer digital camera that does not have a separate analog log compressor.
I have taken a test shot in V-LOG as well as other standard Photo Styles with my Lumix S5 those are the RAW previews. V-LOG is exactly 2 2/3 stops underexposed on a linear scale all other parameters are identical.
What is happening here? As we have seen ISO values have to be the same between photo styles and refer to 18% middle grey however if you apply a log conversion to a digital signal this results in a very bright image. I do some wide field astrophotography and I use a tool called Siril to extract information from very dark images this helps visualise the effect of a log compression.
The first screenshot is the RAW file as recorded a very dark black and white image as those tools process separately RGB.
The second image shows the same RAW image with a logarithmic operator applied; this gives a very bright image.
Now if you have to keep the same middle grey value exposure has to match that linear image so what Panasonic does is to change the mapping of ISO to gain. Gain is the amplification on the sensor chip and has values typically up to 24-30 dB or 8 to 10 stops. While in a linear image the ISO would be defined as 100 at zero gain (I am simplifying here as actually even at 100 there will be some gain) in a log image zero gain corresponds to a different ISO value. So the mapping of ISO to gain is changed. When you read that the native ISO is 100 in normal mode and 640 in V-LOG this means that for the same gain of 0 dB a standard image looks like ISO 100 and a V-LOG image looks like ISO 640, this is because V-LOG needs less gain to achieve the same exposure as the log operator brightens the image. In practical terms the raw linear data of V-LOG at 640 is identical to an image taken at 100.
This is the reason why when a videographer takes occasional raw photos and leaves the camera in V-LOG the images are underexposed.
The benefit of the LOG implementation is that thanks to log data compression you can store the complete sensor information in a lower bit depth in our case this means going from 14 to 10 bits.
There are however some drawbacks due to the fact that at linear level the image was ‘underexposed‘, I put the terms in italic as exposure only depends on time and aperture of the lens, so in effect is lack of gain for which there is no term.
The first issue is noise in the shadows as those on a linear scale are compacted, as the image is underexposed: a higher amount of noise is present and this is then amplified by the LOG conversion. It is not the case that LOG does not have noise reduction, in fact standard noise reduction expects a linear signal gamma corrected and therefore could not work properly (try setting a high value in V-LOG on a S camera to see the results), the issue is with the underexposure (lack of gain) of the linear signal.
There are also additional side effects due to what is called black level range, I recommend reading on photonstophotos a great website maintained by Bill Claff. When you look at black levels you see that cameras do not really have pure black but have a range. This range results in errors at the lower scale of the exposure; the visible effect is colour bleeding (typically blue) in the shadows when there is underexposure. As V-LOG underexposed in linear terms you will have issues of colour bleeding in the shadows: those have been experienced by several users so far with no explanation.
The other side effect is that the LUT to decompress V-LOG remains in a 10 bit color space which was insufficient to store the complete dynamic range data and this does not change. So the LUT does not fully reverse the log compression in Panasonic case this goes into the V709 CineLike Gamma which is in a Rec709 gamma. As the full signal is not decompressed means that there are likely errors of hue accuracy so V-LOG does not have a better ability to reproduce accurate colors and luminance and this is the reason why even after a LUT is applied it needs to be graded. If you instead decompress V-LOG in a log space like Rec2020 HDR you will see that it does not look washed out at all and colors are much more vibrant as the receiving space has in excess of 20 stops.
Some users overexpose their footage saying they are doing ETTR. Due to the way log is implemented this means it will reach a clipping point sooner and therefore the dynamic range is no longer preserved. This is a possible remedy to reduce the amount of noise in low light however the log compression is not fully reversed by the LUT that is expecting middle grey exposure and therefore color and luminance accuracy errors are guaranteed. If you find yourself regularly overexposing V-LOG you should consider not using it at all.
Shadow Improvement and input referred noise
The Lumix cameras with dula gain sensor have a different behaviour to those without. This is visible in the following two graphs again from Bill Claff excellent website.
The first is the shadow improvement by ISO here you can see that while the GH5/G9 stay flat and are essentially ISO invariant, the GH5S and S5 that have a dual gain circuit have an improvement step when they go from low to high gain. What changes here is due to the way the sensors of the GH5s and S5 are constructed, the back illumination means that when the high gain circuit is active there is a material improvement in the shadows and the camera may even have a lower read noise at this ISO (gain) point than it had before because of this.
Another benefit of dual gain implementation is easier to understand when you look at input referred noise graphs. You can see that as the sensor enters the dual gain zone the input referred noise drops. Input referred noise means the noise that you would need to feed as an input to your circuit to produce the same noise as output. So this means when that step is passed the image will look less noisy. Again you can see that while the GH5 stays relatively flat the GH5s and S5 have a step improvement. Is it is not totally clear what happens in the intermediate zone for the GH5s possibly intermediate digital gain or more noise reduction is applied.
The combination of a certain type of sensor construction and dual conversion gain can be quite useful to improve shadows performance.
Do not confuse dual gain benefit with DR preservation, while dual gain reduces read noise it does not change the fact that the highlights will clip as gain is raised. So the effective PDR reduces in any case and is not preserved. The engineering DR is preserved but that is only useful to a machine and not to our eyes.
Now we are going to look at specific implementation of V-LOG in various camera models.
Front Illuminated 12 bits Sensors
Those are traditional digital cameras for photos and include the GH5, G9 for example. On those cameras you will see that the V-Log exposure shows a higher ISO value of 1 stop compared to other photo styles at identical aperture and shutter speed setting but the actual result is the same in a raw file so your RAW at 400 in VLOG is the same of another photo style at 200. This is a direct contradiction of Panasonic own V-Log model as the meter should read the same in all photo styles so something is going on here. As there is no underexposure it follows that there is no real log compression either. Those cameras are designed in a traditional way so low ISO (gain) is good high ISO (gain) is not. This is visible in the previous graphs.
Those screenshot show how the raw data of an image taken at ISO 250 in standard mode is identical to the V-LOG image and therefore shows how there is not LOG compression at all in the GH5. V-LOGL of the GH5 is therefore just a look and does not have any increase of dynamic range compared to other photo styles.
Is this version of V-LOGL more effective than other photo style with a compressed gamma like CineLikeD? According to Panasonic data CineLikeD has 450% headroom so it is already capable of storing the whole dynamic range that the GH5 can produce (450% means 12.13 stops vs 12.3 theoretical maximum).
In addition noise performance of V-Log is worse because all is doing is acting on shadows and highlights and not really doing any log conversion. The business case for acquiring a V-Log key on those cameras is limited if the objective was to preserve dynamic range as the camera already has this ability with photo styles included with the camera and moreover the V-LOG is not actually anything related to LOG compression otherwise the image would have needed to have less gain and would have shown underexposed. The fact that the camera is shooting at nominal ISO 400 means most likely that some form of noise reduction is active to counter the issue that V-Log itself introduces of noise in the shadows. So in this type of camera V-LOG is only a look and does not accomplish any dynamic range compression.
Back Illuminated 12 bits readout sensors
The cameras that have this technology are the GH5s and the BGH1, the back illumination gives the sensor a better ability to convert light into signal when illumination levels are low. Those cameras have actually a sensor with an 14 bits ADC but this is not used for video.
In order to decompose the procedure I have asked a friend to provide some RAW and Jpeg images in Vlog and normal. You can see that in the GH5s there is 1 stop underexposure and therefore a light form of log compression.
In the GH5s implementation the camera meters zero at the same aperture shutter and ISO in LOG and other photo styles and zero is 50% IRE so actually is 1 stop overexposed.
The procedure for V-Log in this cameras is as follows:
Meter the scene on middle grey + 1 stop (50%)
Reduce gain of the image 1 stop behind the scenes (so your 800 is 400 and 5000 is 2500)
Digital log compression and manipulation
As the underexposure is mild this means the log compression is also mild as it is only recovering 1 stop as the two effect cancels this is actually a balanced setting.
The IMX299 dual gain implementation was a bit messed up in the GH5s but has been corrected in the BGH1 with the values of 160 and 800. It is unclear what is happening to the GH5s and why Panasonic declared 400 and 2500 as the dual gain values as those do not correspond to sensor behaviour, perhaps additional on sensor noise reduction only starts at those values or just wanting to make a marketing statement.
Back Illuminated 14bits Sensors
Here we have the S1H and S5 that have identical sensors and dual gain structure.
The metering behaviour on the S series is the same as the GH5s so all photo styles result in identical metering. The examples were at the beginning of this post so I am not going to repeat them here.
Now the gain reduction is 2 and ⅔ stops which is significant. After this is applied a strong log compression is performed. This means that when you have ISO 640 on the screen the camera is actually at gain equivalent to ISO 100 and when you have 5000 is at 640 resulting in very dark images. In the case of the S5/S1H VLOG does offer additional dynamic range not achievable with other photo styles.
Interestingly V-Log on the S series does achieve decent low light SNR despite the strong negative gain bias. Here we can see that the Log implementation can be effective however other photo styles that do not reduce gain may be a better choice in low light as gain lifts the signal and improves SNR. It is also important to note that the additional DR of VLOG compared to other photo styles is in the highlights so it only shows on scenes with bright areas together with deep darks this was noted on dpreview and other websites.
Should you use V-LOG?
It looks like Panasonic is tweaking the procedure for each sensor or even camera as they go along. The behind the scenes gain reduction is really surprising however it is logical considering the effect of a log compression.
Now we can also see why Panasonic calls the GH5s implementation V-LOGL as the level of log compression is small only 1 stops as opposed to VLOG in the S series where the compression is 2 ⅔ stops. We have also seen that V-LOG, at least in a digital consumer camera with sensor with integrated ADC, has potentially several drawbacks and those are due to the way a camera functions.
Looking at benefits in terms of dynamic range preservation:
GH5/G9 and front illuminated sensor: None
GH5s/BGH1 back illuminated MFT: 1 stop
S5/S1H full frame: 2 ⅔ stops
What we need to consider is that changing the gamma curve can also store additional dynamic range in a standard video container. Dpreview is the only website that has compared the various modes when they reviewed the Panasonic S1H.
A particularly interesting comparison is with the CineLikeD photo style that according to Panasonic can store higher dynamic range and is also not affected by the issues of V-LOG in the shadows or by color accuracy problems due to log compression. The measures of dpreview show that:
On the GH5s V-LOG has 0.3 stops benefits over CineLikeD
On the S1H V-LOG has a benefit of 0.7 stops over CineLikeD2
Considering the potential issues of noise and color bleeding in the shadows together with hue accuracy errors due to the approximation of the V-LOG implementation I personally have decided not to use V-LOG at all for standard dynamic range but to use it for HDR footage only as the decompression of V-LOG seems to have limited to no side effects. In normal non HDR situations I have shot several clips with V-LOG but I never felt I could not control the scene to manage with other photo styles and the extra effort for a maximum benefit of 0.7 Ev is not worth my time nor the investment in noise reduction software or the extra grading effort required. As HDR is not very popular I have recently stopped using V-LOG altogether due to lack of support of HDR in browsers for online viewing.
Obviously this is a personal consideration and not a recommendation however I hope this post helps you making the right choices depending on what you shoot.
This write up is based on my analysis on Panasonic V-LOG and does not necessarily mean the implementation of other camera manufacturers is identical however the challenges in a digital camera are similar and I expect the solutions to be similar too.
I have been shooting MFT underwater since 2014 coming from compacts but I have also owned DSLR cameras for land use. As I initially focussed my underwater imaging on video I adopted Panasonic MFT cameras as they have an edge in terms of video use coming from Panasonic long established video and broadcast legacy.
Recently, just days before the divestiture announcement, I have purchased an Olympus OMD EM1MKII. I have decided on this camera as during lockdown I have been attempting pictures of birds in flight and the autofocus of my Panasonic G9, that I was using since February for land pictures, was not satisfactory.
I have since pondered if it made sense to switch to Olympus also for underwater use and I have considered the pro and cons of this choice compared to Panasonic semi pro models GH5 and G9. I thought of sharing my thinking with you so that if you are considering an MFT system as your next investment for underwater imaging you have a point of reference.
Note: I am only considering the top range Olympus cameras as others do not offer in my opinion any benefit over Panasonic range.
Strengths of OMD System
Olympus OMD Auto Focus system
At time of writing the OMD EM1 series and the EM5 Mark III use an Olympus specific on sensor phase difference detection auto focus system. Note this is different to DSLR phase detection and more similar to Sony hybrid AF system.
I found this system to be very effective with birds in flight once locked on the subject and much faster in locking on subjects as long as the background was clear; with this I mean this system still struggles if there is a busy background to acquire focus. In particular the CAF with tracking is very effective for birds that do not move too fast in the air or are about to take off from a fixed spot. It also effectively tracks at higher frame rate any type of object in motion. This system is superior to Panasonic CAF that is based on motion estimation for shots following the first one of the burst. More specifically it is harder to acquire focus for the first time with Panasonic and the following shots are estimated using a motion prediction algorithm without continuous autofocus. This feature is the one that sets Olympus camera that have phase detection AF apart from Panasonic and from more economic Olympus model such as the OMD EM10 series. Another useful feature is that in review mode it tells you what the camera focussed on.
Other features of OMD system for land use
If you shoot at night another very useful feature is live composition, this is very useful for fireworks or star trails but not effective for real astrophotography for which you need a star tracker or use stacking. Other features that are present in the newer EM1MKIII like starry AF are in my opinion not useful if you know how to focus on stars.
Olympus Housing Costs
As Olympus bodies are smaller and simpler the housing cost compared to Panasonic G and GH series is 30% lower this is material in the scheme of things as Panasonic Pro housing are almost as expensive as an APSC DSLR. This for me is the single most important factor.
Drawbacks of Olympus Cameras
Lack of on Screen Manual Focus Guide
The most evident one for macro shooters is the lack of on screen MF guide as displayed in Panasonic cameras. This very useful for macro but also for astrophotography and video as you know if your camera is at the macro or tele end. For macro underwater photography this means you know if you have hit the minimum working distance and maximum magnification so now you can focus on getting the shot using peaking.
Olympus does not offer a guide but you can pre-set a mode called Pre-MF to minimum distance however I found the on screen peaking to be really poor and ultimately getting less magnification in macro shots.
While Panasonic offers customisable Zebra on screen Olympus only offers a red and blue colouring and the levels only offer limited customisation on a 0-255 8 bits scale. This is OK for checking clipping in absolute but not good for specific exposure targets.
The video modes of the OMD are simply poor and the codec quality just good for your occasional video. The lack of exposure aid and support for manual focus make the whole video experience very very dissatisfactory.
With Panasonic you can set framing guides on the screen for 1:1 5:4 whatever you like without changing the image aspect ratio, this is useful if you want to frame a shot for a specific platform. Olympus lacks this feature entirely.
I can confirm that for underwater and land use I see zero difference in performance between my OMD EM1MKII and the GH5 in the range ISO 200-1600. It is true that the Jpeg settings are different and the color rendering is different for Jpeg however shooing RAW files this becomes irrelevant and I can’t distinguish the shots when the calibrated adobe profiles are used in Lightroom. I believe at some point that Olympus images were sharper however this was due to the images being better in focus when it comes to birds and subjects fast moving.
In terms of JPEG rendering Olympus choices are better for nature and landscapes with more saturated colours, for portraits I prefer the Panasonic rendering. Again those settings are not relevant for RAW files.
In my opinion the most attractive feature of Olympus cameras for underwater photography use is actually the reduced cost and size of the housing. While the extra strength are surely worth for land wildlife photography I truly do not think they make any difference underwater. For sure it would be better to do a field test, this so far has not been possible and if anybody gives me an OMD EM1MKII housing to test I would be very happy, however using the tools made available by Panasonic I do not get almost any shots out of focus and those there are blurred are because I forgot to change a setting on the camera.
For video I cannot recommend the Olympus system at all, Panasonic is way ahead on this on a number of accounts.
In conclusion if you are 100% focus on photography and just take an occasional video the OMD system is light more compact and less expensive. It will not give any edge to your images as the sensors are identical. If you shoot a mix of video and photos the choice is Panasonic. Rest assured none of the AF strength of Olympus will improve your hit rate, if your shots are blurred you are likely using the wrong settings with your camera. The housing costs tho are higher and the rigs are less portable.
In light of Covid-19 many long haul destinations are still closed and may potentially be for a long time so your UW photography gear may collect a good amount of dust…unless you join me for this wonderful trip, on the gulf of Naples, in the marine protected area of Punta Campanella.
Strategically located and fronted by the island of Capri Punta, Campanella offers exhilarating dives with schools of snappers, large groupers, thousands of barracudas as well as wonderful red and white gorgonians. It also offers caves, macro and amazing night dives.
More information on the website of Punta Campanella.
The area is also home to Mimmo Roscigno, a super talented local underwater photographer, who published a book on the fish life found in the area.
On top of that the area offers amazing food and views. Capri, Pompei and Positano are nearby if you fancy a trip during the degassing day.
Accommodation will be at Sea Breeze Residence that is 2 minutes walk from the marina and meals will be at the Paguro restaurant on the jetty, serving fresh food with local produce and fish.
13 September Arrival in Naples. Transfer to Massa Lubrense. Light Lunch. 1530 Mandatory Check Dive. Transfer to Massa Lubrense. Check in at Sea Breeze Residence
19 September. Degassing day. Free time to explore the area (Capri, Positano, Pompei are nearby)
20 September 6.30 AM departure to Airport. 10:35 Departure to destination
Night Dives €40
Diving Baia Archaeological Park (transfer costs only, dependant on number of participants)
Flights (average price at time of writing is under £100 excluding luggage)
Price €1,350 excluding flights includes 15 litres tanks
Due to the heavy discounts involved, a non refundable €350 deposit is required by 31st of August to block the rooms.
Covid-19 disclaimer: all operations and the hotel adopt regulation as mandated by local authorities. Room rates are based on single occupancy, double occupancy is allowed for member of the same household but will not grant any further discount on the quoted prices. In case of lockdown of the area of additional UK restriction towards Naples the trip will be postponed at no extra charge.
There is no doubt that until a Covid-19 vaccine is widespread our travel plans have to adjust to the new conditions. As of today 2 August 2020 most of our favourite destinations are still in the no go list and are not covered by travel insurance.
The latest list of countries and territories published by the British FCO does not include Egypt, Indonesia, Philippines and no countries in South America although it does have many Caribbean destinations.
With the situation evolving fast and the imminent prospect of tighter lock down as we go towards winter many people would not travel long haul anyway to avoid risks of quarantine or possible issues coming back to their home country. So for now, many of us will travel more locally. We have seen lots of new underwater photographs taken locally in British Waters but there is no doubt this is not out of choice and most people would rather be elsewhere.
After the postponement of my Red Sea live-aboard to 2021 I have been invited to the Italian Nauticam days in Italy in the stunning location of Napoli and Sorrento and coast. I am from the same region and all my diving training has been abroad so I am guilty of not having tried the local diving until now. If you don’t want to read the whole article the summary is that the diving is great and combined with the natural beauty of the area, the warmth of the local and the food and drink there is probably no better alternative for diving safe in Covid-19 times in Europe right now. I am sure there are equally stunning places in Liguria and some of the Sicilian or Tuscany locations however the Penisola Sorrentina is very hard to beat when you consider the other elements. Please get in touch if you want to dive the area as I am planning a trip mid September 2020.
The Diving Centre and Location
I used Punta Subaia and Punta Campanella Diving centre two long standing operations on the coast. The first is located in Bacoli north of Naples and the second is in Massa Lubrense just past Sorrento. Bacoli is Naples local beach so gets more local traffic while the other location is more touristic in nature with a good ratio of foreigners: during my stay there were English, German, French, Swiss and Dutch on the dives.
I used a 5mm wetsuit with a 3mm hooded vest and a thermal top under and was fine. Locals dive with a 7/5mm semidry suit.
Diving is done using 7.5 meters RIBs that can take up to 8 divers on a double tank or 12 on a single tank dive. Covid-19 procedures are in place and face masks are not mandatory outdoors in Italy however spacing on the RIB is challenging so you have checks and declarations to fill in. Some people wear face masks on the boat too is entirely up to you.
Journey time to the dive sites is 5 minutes in Baia while in Punta Campanell it can be up to half hour and the scenery is amazing as Capri is just in front of the coast and the landscape is jut breathtaking.
If there is one thing that I did not like is that in the morning there was not a systematic double tank excursion so sometimes the day would finish at 6 pm with only 3 dives done. Crew are very helpful and 15 litres tanks are included at no extra so in all cases I came up because I reached the 1 hour limit still having plenty of air.
I booked a double room with single occupancy at €80 per night B&B 2 minutes walk to the dive centre. Food and drinks with wine runs at €50 or less per day and is glorious!
If you want to have an idea of the critters in the area I would recommend the book Into the Mirror from Mimmo Roscigno ISBN: 9788890966804 is only in Italian but it is a typical coffe table book the images are simply amazing.
For wide angle a good sample is on Punta Campanella Dive Center website, also look for photographers Marco Gargiulo that is local of the area. Other photographers like Franco Banfi have also been here for workshops. So there has been some fame but mostly limited to Italian speaking photographers, this is a shame as the staff speaks English and this is a photo friendly operation.
I went for this trip with a selection of wide angle lenses, I had been told by Pietro Cremone about the underwater archeology park so I packed a rectilinear wide angle in order to avoid distortion.
Dives in Subaia are typically 1 hour long max by law at depth of 5 meters.
The dives have to be done with an expert guide as the mosaics are normally hidden to protect from the agents and the water.
There are also replica statues that are good subjects, the originals are in the Napoli Museum.
There are many villas and it is impossible to cover the grounds in two dives however I had planned to move to the second location so I drove two hours to Massa Lubrense on the night.
Here the diving is about fish and caves. You have a combination of close up subjects and wide angle. I took by zoom fisheye with me so I focussed on wide angle. Sea life includes plenty of Anthias and Damsel, Snappers, large groupers, eagle rays, breams, bass there is a lot of fish as the area has been a protected marine park for more than 20 years now. I was not expecting this abundance, there is also a resident shoal of Barracudas 1000+ strong specimen that is in shallow water at one of the sites. Due to limited processing power I have not yet created a 4K video however I took plenty of shots. The whole album is on flickr. I hereby include some key shots.
I was frankly surprised by the sheer abundance of photo opportunities and I will be always taking my equipment whenever I go back to Italy in the summer. There are so many positives to the location:
Great photo opportunities
Well organised dive operation English speaking and photo friendly
Stunning location also for non divers
Easy to reach from UK and other EU countries
Covid-19 procedures in place safe location with prime health system
I am so impressed by the location that I will be back and in fact I am planning a photo trip the week of 14 or 21 September, with the following itinerary:
Sunday arrival dinner with local photographers to have a taste of the area
Monday to Friday double tank morning dive, afternoon optional 3rd dive or sightseeing
Photos of the day debrief after dinner time – optional
Saturday no dive day local trips optional or travel independently
Sunday free morning transfer to airport and return
Diving cost is €400 for 5×2 tank dives to be booked in advance through me. For those we will have exclusive use of the boat optional dives in the afternoon non exclusive will be €35 per dive. Accommodation will be typically less than €600 euro for the week in single occupation and plane in the region of £100-150 depending on extras. I can help with accommodation, travel and transfers. You can also rent a car as low as £15 per day this is especially of value if planning to come with partner or family.
Please fill the contact form if interested spaces will be limited to maximum 8 for the trip. I think it will be a long time for anyone to be in tropical waters with the Covid-19 situation, this is an opportunity not to be missed until the water stays warm and enjoy one of the world very best destinations.
Due to Covid-19 I have decided to postpone the boat to 31 July 2021. I have also had some cancellations due to the same reason so currently have 7 spaces. Prices remain unchanged. What follows is content from the original post.
Diving for images or video can be frustrating at times. I find this less so for macro and super macro where you are resort based and you can hire a guide with super sharp eyes that will help you find the right subjects. For wide angle it is a totally different story. Land based may preclude the best access to certain destinations whilst if you are on a liveaboard with divers there is a conflict of interest. The boat will typically run a fixed itinerary cruise and the result is that you will visit many times so more memorable than others and typically just once. The single dive you do may not be at the right time of the day and the ambient light may not be the best for what you trying to do.
I am self taught and I like to read books and experiment myself however some years ago I was invited by Nauticam to a Red Sea workshop with Alex Mustard.
What I really liked about that workshop was the ability to steer the boat to the right sites, to be able to dive at the right time of the day and also to repeat dives on the best sites and omit the areas that were not promising. For me this had great value on its own.
Of course Dr Alex Mustard tuition was also superb however I have now done this workshop 3 times and I believe that element has become less interesting. I also happened to work in Sharm El Sheikh as resident instructor at the Marriot Hotel so all dive sites were already known to me as a diver at least.
On those workshops I found very useful the fact that you could see the work of others and learn from the group, I also like the fact that there was no competition so everybody was encouraged to share.
Needless to say that after years of diving the same sites I still find the Northern Wreck and reefs of the Red Sea one of the best imaging destination in the world so I thought how do I have the same experience without the workshop part and the related high costs – it costs almost double a standard diving trip to book Alex workshop and they are fully booked almost immediately.
A further issue that has occurred in time is that there are no flights to Sharm El Sheikh from UK and now majority of boats live from Hurghada. This seriously limits the workshop as you have a lot more navigation.
So my ideal requirements for such a trip would be:
Boat to live from Sharm El Sheikh not Hurghada. I rather have indirect flights and burn land time vs consuming cruise time in transfers
Need to be able to have full control of the itinerary
Dive as a photographer with a loose buddy concept
Have a good boat and logistics
Have small number of people in the water – I think 20 is too much so I have set my target to 8 min 12 max
I reconnected with my old network and after looking around I have found a boat and a company that can help with this.
King Snefro is the only liveaboard fleet currently departing from Sharm El Sheikh and the boat of choice is the Snefro Pearl
Cruise Dates: 31 July – 7 August 2021
Price: €1250 per Pax in twin cabin includes:
12 Liter tanks
3 meals, snacks and soft drinks, tea and coffee
Special imaging orientated dive briefing to make the most of the sites
Group image debrief – optional participation
Arrival on Saturday 31st July – check in commences at 1800
Check out Saturday 7th August – 1200 latest
For those whose flight leaves much later possibility of a stop gap in a beach resort before final departure
You need to be a PADI Advanced Open Water Diver or equivalent and 30 logged dives are required for this safari. All dives, especially some more demanding wreck dives, are subject to diver’s qualification and experience.
EAN or other Nitrox certification required if not training will be provided on the boat at a charge.
Extra Hotel arrangements if you are coming the day before or leaving the day after
Halfboard in Single Room = 50 € per night per person Soft All in per in Single room = 60 € per night per person
Halfboard in Double Room = 35 € per night per person Soft All in Double room = 45 € per night per person
Halfboard in Triple Room = 30 € per night per person Soft All in Triple room = 40 € per night per person
Service Charge & taxes included, Transfer Airport to Hotel/ Hotel to Airport is included (Check in starts from 14:00 H, Check out till 12:00 H, in combination with safari booking early check in or late check out will be arranged free of charge)
On to the dive sites:
Wrecks of Abu Nuhas
Ras Za’tar (Optional site for sunbursts)
Jackfish Alley – Optional site for caves
Ras Mohammed where at that time of the year you can have various shoals of fish
Instead of night dives we will do snorkelling session for split shots or sunset dives
I will be glad to help with ideas for the sites or the shots to take however this is not for beginners so if you don’t know even how to work out your camera works maybe it is not for you. The trip is open to photographers and videographers I will shoot both and will provide assistance as required. Below little sample of the video opportunity in Shark Reef
Please use the form to book a space. In case the cruise it is sold out I will operate strictly a first come first serve basis at time of writing there are five space left so hurry up. In case of cancellation I will also run a wait list. Please inquiry for any other details as well
We are finally there. Thanks to smaller companies that are keen to get a share of the market we now have at least two cameras with MFT sensor that are able to produce RAW video.
RAW Video and RED
It has been RED to patent the original algorithm to compress raw video data straight out of the sensor before the demosaicing process. Apple tried to circumvent the patent with their ProRes RAW but lost in court the legal battle and now has to pay licenses to Red. Coverage is here.
So RED is the only company that has this science, to avoid paying royalties Blackmagic Design developed an algorithm that uses data taken from a step of the video pipeline after demosaic for their BRAW.
I do not want to discuss if BRAW is better than RedCode or ProRes RAW however with a background in photography I only consider RAW what is straight out of the sensor Analag Digital Converter so for me RAW is RedCode or ProRes RAW and not BMRAW.
How big is RAW Video
If you are a photographer you know that a RAW image data file is roughly the same size in megabytes than the megapixels of your camera.
How is that possible I have a 20 Megapixel camera and the RAW file is only a bit more than 20 megabytes? My Panasonic RW2 files are 24.2 MB without fail out of 20.89 Megapixels so on average 9.26 bits per pixel. Why don’t we have the full 12 bits per pixel and therefore a 31 MB file? Well cameras are made of a grid of pixels that are monochromatic so each pixel is either red, green or blue. In each 2×2 matrix there are 2 green pixels, 1 red and 1 blue pixel. Through a series of steps of which on is to decode this mosaic into an image (demosaic) we rebuild an RGB image for display.
Each one of our camera pixels will not have the full 4096 possible tones, measures from DxoMark suggest that the Sony IMX272AQK only resolves 24 bits colours in total and 9 bits of grey tones. So this is why a lossless raw files is only 24.2 MB. This means that an 8K frame video in RAW would be 9.25 MB and therefore a 24 fps RAW video stream would be 222 MB/s or 1,776 Mb/s if we had equivalent compression efficiency. After chroma subsampling to 422 this would become 1184 Mb/s.
Cameras like the ZCam E2 or the BMPCC4K that can record ProRes 422 HQ approach those bitrates and can be considered virtually lossless.
But now we have ProRes RAW so what changes? The CEO of ZCAM has posted an example of a 50 fps ProRes RAW HQ files and this has a bitrate of 2255 Mb/s if this was 24 fps it would be 1082 Mb/s so we can see how my maths are actually stacking up nicely.
Those bit rates are out of reach of almost all memory card so an SSD drive support is required and this is where Atomos comes into the picture.
Atomos have decided to adopt ProRes RAW and currently offer support for Nikon, Panasonic and Zcam selected model.
ProRes RAW workflow
So with the ProRes RAW file at hand I wanted to test the workflow in Final Cut Pro X. Being an Apple codec all works very well however we encounter a number of issues that photographers have resolved a long time ago.
The first one is that RAW has more dynamic range than your SDR delivery space, this also happens with photos however programs work in larger RGB spaces like ProPhotoRGB at 16 bits and using tone mapping you can edit your images and then bring them back to an 8 bit jpeg that is not as good as the RAW file but is in most cases fine for everyone.
Video NLE are not in the same league of photo raw editors and usually deal with a signal that is already video is not raw data. So the moment you drop your ProRes RAW clip on a SDR timeline it clips as you would expect. A lot of work is required to bring back clips into an SDR space and this is not the purpose of this post.
To avoid big issues I decided to work on an HDR timeline in PQ so that with a super wide gamut and gamma there were no clipping issues. The footage drops perfectly into the timeline without any work required to confirm which is brilliant. So RAW for HDR is definitely the way forward.
ProRes RAW vs LOG
My camera does not have ProRes RAW so I wanted to understand what is lost going through LOG compression? For cameras that have an analog gain on sensor there is no concept of base ISO fixed like it happens on Red or ARRI cameras. Our little cameras have a programmable gain amplifier and as gain goes up DR drops. So the first bad news is that by using LOG you will lose DR from RAW sensors.
This graph shows that on the Panasonic GH5 there is a loss of 1 Ev from ISO 100 to 400 but still we have our 11.3 Ev minimum to play with. I am not interested in the whole DR but I just want to confirm that for those cameras that have more DR than their ADC allows you will have a loss with LOG as this needs gain and gain means clipping sooner.
What is very interesting is that net of this the ProRes RAW file allowed me to test how good is LOG compression. So in this clip I have :
RAW video unprocessed
RAW video processed using Panasonic LOG
RAW video processed using Canon LOG
RAW video processed using Sony LOG
In this example the ZCAM E2 has a maximum dynamic range of 11.9 Ev (log2(3895)) from Sony IMX299CJK datasheet. As the camera has less DR than the maximum limit of the ADC there is likely to be no loss.
We can see that there are no visible differences between the various log processing options. This confirms that log footage is an effective way to compress dynamic range in a smaller bit depth space (12->10 bits) for MFT sensors.
Final Cut Pro gives you the option to go directly to RAW or go through LOG, this is because all your log based workflow and LUT would continue to work. I can confirm this approach is sound as there is no deterioration that I can see.
Is ProRes RAW worth it?
Now that we know that log compression is effective the question is do I need it? And the answer is it depends…
Going back to our ProRes RAW 1082 Mb/s once 422 subsampling is applied this drops to 721 Mb/s this is pretty much identical to ProRes 422 HQ nominal bit rate of 707 Mb/s. So if you have a Zcam and record ProRes RAW or ProRes 422 HQ you should not be able to see any difference. I can confirm that I have compressed such footage in ProRes 422 HQ and I could not see any difference at all.
However typically with photos a RAW files can hold heavy modifications while a JPEG cannot. We are used processing ProRes and there is no doubt that ProRes 422 HQ can take a lot of beating. In my empirical tests I can see that Final Cut Pro X is very efficient manipulating ProRes RAW files and in terms of holding modifications I cannot see that this codec provides a benefit but this may be due to the lack of capability of FCPX.
For reference Panasonic AVC Intra 422 is identical in terms of quality to ProRes 422 HQ though harder to process, and much harder to process than ProRes RAW.
If you have already a high quality output from your camera such as ProRes 422 HQ or Panasonic AVCI 400 Mbps with the tools at our disposal there is not a lot of difference at least for an MFT sensor. This may have to do with the fact that the sensor DR and colour depth is anyway limited and therefore log compression is effective to the point that ProRes RAW does not appear to make a difference, however there is no doubt that if you have a more capable camera, there is more valuable data there and this may be well worth it.
I am currently looking for Panasonic S1H ProRes RAW files. Atomos only supports 12 bits so the DR of the camera will be capped as RAW is linearly encoded. However SNR will he higher and the camera will have more tones and colors resulting in superior overall image quality, someone calls this incorrectly usable DR but is just image quality. it will be interesting to see if AVCI 10 bits and log is more effective than ProRes RAW 12 bits.
In order to product HDR clips you need HDR footage. This comes in two forms:
Cameras have been shooting HDR since years the issue has been that no consumer operating system or display were capable of displaying it. The situation has changed as Windows 10 and Mac Os now have HDR-10 support. This is limited for example on Mac Os there is no browser support but the Tv app is supported, while on windows you can watch HDR-10 videos on YouTube.
You need to have in mind your target format because Log and HLG are not actually interchangeable. HLG today is really only Tv sets and some smartphones, HDR-10 instead is growing in computer support and is more widely supported. Both are royalty free. This post is not about what is the best standard is just about producing some HDR content.
The process is almost identical but there are some significant differences downstream.
Let me explain why this graph produced using the outstanding online application LutCalc show the output input relationship of V-LOG against a standard display gamma for rec709.
V-LOG -> PQ
Looking at the stop diagram we can appreciate that the curves are not only different but a lot of values differ substantially and this is why we need to use a LUT.
Once we apply a LUT the relationship between V-LOG and Rec709 is clearly not linear and only a small parts of bits fit into the target space.
We can see that V-Log fills Rec709 with just a bit more than 60% IRE so there will need to be a lot of squeezing to be done to fit it back in and this is the reason why many people struggle with V-Log and the reason why I do not use V-Log for SDR content.
However the situation changes if we use V-Log for HDR specifically PQ.
You can see that net of an offset the curves are almost identical in shape.
This is more apparent looking at the LUT in / out.
With the exception of the initial part that for V-Log is linear while PQ is fully logarithmic the curve is almost a straight line. As PQ is a larger space than that V-Log can produce on a consumer camera we do not have issues of squeezing bits in as PQ accommodates all bits just fine.
Similar to V-LOG HLG does not have a great fit into an SDR space.
The situation becomes apparent looking at the In/Out Lutted values.
We can see that as HLG is also a log gamma with a different ramp up 100% is achieved with even less bits that V-Log.
So really in pure mathematical terms the fit of log spaces into Rec709 is not a great idea and should be avoided. Note with the arrival of RAW video we still lack editors capable to work in 16 bit depth space like photo editors do and currently all processes go through LOG because they need to fit into a 10/12 bits working space.
It is also a bad idea to use V-Log for HLG due to the difference of the log curves.
And the graph demonstrates what I said at the beginning. You need to decide at the outset your output and stick to a compatible format.
Importing Footage in Final Cut Pro X 10.4.8
Once we have HLG or LOG footage we need to import it into a Wide Gamut Library, make sure you check this because SDR is default in FCPX.
HLG footage will not require any processing, but LUTs have to be applied to V-LOG as this is different from any Rec2100 target spaces.
The most convenient way is to go into Organise workspace select all clips than press the i button and select General. Apply the Panasonic V-Log LUT to all clips.
Creating a Project
Once all files have been handled as required we create our HDR-10 project which in final cut means Rec2020 PQ.
The following screenshots demonstrate the effect of the LUT on footage on a PQ timeline.
With the LUT applied the V-LOG is expanded in the PQ space and the colours and tones come back.
We can see the brightness of the scene is approaching 1000 nits and looks exactly we we experienced it.
Once all edits are finished and just as last step we add the HDR Tools to limit peak brightness to 1000 Nits which is a requirement of YouTube and most consumer displays. The Scope flex slightly with an automatic highlight roll-off.
Exporting the Project
I have been using Panasonic AVCI 400 mbps so I will export a master file using ProRes422 HQ if you use a lower bitrate ProRes 422 may be sufficient but don’t go lower as it won’t be HDR anymore.
YouTube and other devices use default settings for HDR-10 metadata so do not fill the mastering display nor content information it is not required and you would not know how to fill it correctly with exception of peak brightness.
Converting for YouTube
I use the free program handbrake and YouTube guidelines for upload to produce a compatible files. It is ESSENTIAL to produce an mp4 file otherwise your TV and YouTube may not be able to display HDR correctly avoid any other format at all costs.
The finished product can be seen here
SDR version from HDR master
There are residual issues with this process one is the production of an SDR version. This currently works much better for HLG than HDR-10 which is interesting because HLG is unsupported on any computer so if you produce HDR HLG you are effectively giving something decent to both audiences.
For HDR-10 YouTube applies their own one fits all LUT and the results can be really bad. You may experience oversaturated colours in some cases, dark footage in others, and some clips may look totally fine.
At professional level you would produce a separate SDR grade however it is possible to improve the quality of YouTube conversion using specific techniques I will cover in a separate post.
Grading in HDR is not widely supported the only tools available are scopes and Tone Mapping of your display. There is no concept of correct exposure for skin tones, in one scene those have a certain brightness and in another this changes again because this is not a 0-100% relative scale but goes with absolute values.
If you invested in a series of cinema LUT you will find none of them work and compresses the signal to under 100 nits. So there is less headroom for looks. There are other things you can do to give some vintage look like adding grain but you need to be careful as the incredible brightness of the footage and the details of 10 bits means if you push it up too much it looks a mess. Currently I am avoiding adding film grain and if I add it I blend it to 10%-20%.
One thing that is interesting is that Log footage in PQ does have a nice feel to it despite the incredible contrast. After all Log is a way to emulate film specifically Cineon, this is true for almost all log formats. Then you would have the different characteristics of each film stock, this is now our camera sensor and because most of them are made by Sony or Canon the clips tend to look very similar to each other nowadays. So if you want to have something different you need to step in the world of Red or ARRI but this is not in the scope of what I am writing here and what you my readers are interested in.
Am keeping a playlist with all my HDR experiments here and I will keep adding to it.
If you find this useful please donate using the button on the side and I will have a drink on you…Cheers!
There are significant number of misconceptions about noise in digital cameras and how this depends on variables like the sensor size or the pixel size. In this short post I will try to explain in clear terms the relationship between Signal Noise Ratio (SNR) and sensor size.
Signal (S) is the number of photons captured by the lens and arriving on the sensor, this will be converted in electric signal by the sensor and digitised later on by an Analog Digital Converter (ADC) and further processed by Digital Signal Processors (DSP). Signal depending on light is not affected by pixel size but by sensor size. There are many readings on this subject and you can google it yourself using sentences like ‘does pixel size matter’. Look out for scientific evidence backed up by data and formulas and not YouTube videos.
S = P * e where P is the photon arrival rate that is directly proportional to the surface area of the sensor, through physical aperture of the lens and solid angle of view, and e is the exposure time.
This equation also means that once we equalise lens aperture there is no difference in performance between sensors. Example two lenses with equivalent field of view 24mm and 12mm on full frame and MFT with crop 2x when the lens aperture is equalised produce the same SNR. Considering a full frame at f/2.8 and the MFT at f/1.4 gives the same result as 24/2.8=12/1.4 this is called constrained depth of field. And until there is sufficient light ensures SNR is identical between formats.
Noise is made of three components:
Photon Noise (PN) is the inherent noise in the light, that is made of particles even though is approximated in optics with linear beams
Read Noise (RN) is the combined read noise of the sensor and the downstream electronic noise
Dark Current Noise (DN) is the thermal noise generated by long exposure heating up the sensor
I have discovered wordpress has no equation editor so forgive if the formulas appear rough.
Photo Noise is well mapped by Poisson distribution and the average level can be approximated with SQRT(S).
The ‘apparent’ read noise is generally constant and does not depend on the signal intensity.
While 3 is fundamental to Astrophotography it can be neglected for majority of photographic applications as long as the sensor does not heat up so we will ignore it for this discussion.
If we write down the Noise equation we obtain the following:
Ignoring DN in our application we have two scenarios, the first one is where the signal is strong enough that the Read Noise is considerably smaller than Photon Noise. This is the typical scenario in standard working conditions of a camera. If PN >> RN the signal to noise ratio becomes:
SNR =sqrt S
S is unrelated to pixel size but is affected by sensor size. If we take a camera with a full frame and one with a 2x crop factor at high signal rate the full frame camera and identical f/number it has double the SNR of the smaller 2x crop. Because the signal is high enough this benefit is almost not visible in normal conditions. If we operate at constrained depth of field the larger sensor camera has no benefit on the smaller sensor.
When the number of photons collected drops the Read Noise becomes more important than the photon noise. The trigger point will change depending on the size of the sensor and smaller sensor will become subject to Read Noise sooner than larger sensors but broadly the SNR benefit will remain double. If we look at DxOMark measurements of the Panasonic S1 full frame vs the GH5 micro four thirds we see that the benefit is around 6 dB at the same ISO value, so almost spot on with the theory.
Due to the way the curve of SNR drops the larger sensor camera will have a benefit or two stops also on ISO and this is the reason why DxOMark Sport Score for the GH5 is 807 while the S1 has a sport score of 3333 a total difference of 2.046 stops. The values of 807 and 3333 are measured and correspond to 1250 and 5000 on the actual GH5 and S1 cameras.
If we consider two Nikon camera the D850 full frame and the D7500 APSC we should find the difference to be one stop ISO and the SNR to drop at the same 3 dB per ISO increment.
The graphic from DxoMark confirms the theory.
If the SNR does not depend on pixel size, why do professional video cameras and, some high end SLR, have smaller pixel count? This is due to a feature called dual native ISO. It is obvious that a sensor has only one sensitivity and this cannot change, so what is happening then? We have seen that when signal drops, the SNR becomes dominated by the Read Noise of the sensor so what manufacturers do is to cap the full well capacity of the sensor and therefore cap the maximum dynamic range and apply a much stronger amplification through a low signal amplifier stage. In order to have enough signal to be effective the cameras have large pixel pitch so that the maximum signal per pixel is sufficiently high that even clipped is high enough to benefit from the amplification. This has the effect of pushing the SNR up two stops on average. Graphic of the read noise of the GH5s and S1 show a similar pattern.
Sone manufacturers like Sony appear to use dual gain systematically even with smaller pixel pitch in those cases the benefit is reduced from 2 stops to sometimes 1 or less. Look carefully for the read noise charts on sites like photonsforphotos to understand the kind of circuit in your camera and make the most of the SNR.
Because most of the low light situation have limited dynamic range, and the viewer is more sensitive to noise than DR, when the noise goes above a certain floor the limitation of the DR is seen as acceptable. The actual DR is falling well below values that would be considered acceptable for photography, but with photos you can intervene on noise in post processing but not DR, so highest DR is always the priority. This does not mean however that one should artificially inflate requirements introducing incorrect concepts like Useable DR especially when the dual gain circuit reduce maximum DR. Many cameras from Sony and Panasonic and other manufacturers have a dual gain amplifier, sometimes advertised other times not. A SNR of 1 or 0 dB is the standard to define useable signal because you can still see an image when noise and signal are comparable.
It is important to understand that once depth of field is equalised all performance indicators flatten and the benefit of one format on the other is at the edges of the ISO range, at very low ISO values and very high ISO and in both cases is the ability of the sensor to collect more photons that makes the difference, net of other structural issues in the camera.
As majority of users do not work at the boundaries of the ISO range or in low light and the differences in the more usual values get equalised, we can understand why many users prefer smaller sensor formats, that make not just the camera bodies smaller, but also the lenses.
In conclusion a larger sensor will always be superior to a smaller sensor camera regardless all additional improvement made by dual gain circuits. A full frame camera will be able to offer sustained dynamic range together with acceptable SNR value until higher ISO levels. Looking for example at the Panasonic video orientated S1H the trade off point of ISO 4000 is sufficient on a full frame camera to cover most real-life situation while the 2500 of the GH5s leaves out a large chunk of night scenes where in addition to good SNR, some dynamic range may still be required.