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Red Sea Image Makers 2022 Shot Report

Just back from a fantastic week. Cannot write a trip report on something I arranged however I am confident those will come from the participants.

The actual schedule ended up like this

DateTime inSiteLensVideo
31/7/2208:40TempleCanon 8-15mm
31/7/2211:40Jackfish AlleyCanon 8-15mmYes
31/7/2215.10Beacon RockCanon 8-15mm
31/7/2217:30Beacon RockCanon 8-15mm
1/8/2206:35DunravenPanasonic 8-18mm
1/8/2210:45Small crackPanasonic 8-18mmYes
1/8/2215.30MarcusPanasonic 8-18mm
1/8/2217:00Dolphin SnorkellingPanasonic 8-18mmYes
2/8/2206:20Giannis DPanasonic 8-18mm
2/8/2209:45CarnaticPanasonic 8-18mm
2/8/2215:20ThistlegormPanasonic 8-18mm
3/8/2206:25ThistlegormPanasonic 8-18mm
3/8/2209:45ThistlegormPanasonic 8-18mm
3/8/2214:10RM LighthousePanasonic 8-18mmYes
4/8/2217:30Sandbar trip

4/8/2206:20Shark ReefCanon 8-15mm
4/8/2210:00Shark ReefCanon 8-15mm
4/8/2214:00Ras GhozlaniCanon 8-15mm
4/8/2217:40Sunset SplitsPanasonic 8-18mm
5/8/2207:00Ras Za’tarCanon 8-15mm
5/8/2210:00Ras Umm SidCanon 8-15mm
5/8/2214:20TempleCanon 8-15mm
5/8/2217:40Sunset SplitsPanasonic 8-18mm

I would have preferred a more aggressive approach to some sites however I decided ultimately to settle on something that was challenging diving wise but not extreme.

I used my Panasonic GH5M2 with the Canon EF 8-15mm and the Panasonic 8-18mm. Surprisingly I found I had more keepers with the 8-18mm this is due to the dolphin dive for which I took the risk of using the rectilinear lens and continuous autofocus which worked well.

Day 1

The trip had a slow start at Temple followed by Ras Mohammed and some technical training on light at Beacon Rock.

Pulsating reef life at Temple

Ghost in the Shell

Moray Burst

Day 2

After a dive at Dunraven and a better one at Small Crack where I took video we moved to Abu Nuhas where I decided to skip the last dive and go for a snorkelling trip hoping to get dolphins.

underwater explorers

Inside the Marcos

Wreck diving

Barnacle Bow

The dolphin came to play we had one hour with them swimming at speed around us and getting really close

Lone Dolphin

Spinning
Checking you

Dynamic Duo

Dolphin Photography

Day 3

It was the day of the wrecks including the Thistlegorm in order to support the group I was at the back which did not help visibility. We were mostly on our own though

Giannis Vertical
Red Coral
Giannis bow
Phantom Wreck

Wrapping cloth?
Exploring the stern of the Carnatic
Big fish

Ceiling

Cage

Day 4

Two additional dives on the Thistlegorm and we were back to Ras Mohammed after the adrenalin an easy dive at the lighthouse followed by sunset trip on a sandbar. This time I tried to get some better shots of the Thistelgorm exterior while I would say inside there was generally less fish to make the shot interesting.

Bikes trailer
Truck
Motorbike
The last Steering wheel truck

Headlights

Propeller
Machine Gun

Locomotive

Day 5

Two dives at Shark Reef the current was pumping. We missed the snappers on dive one but they were there in full force with the batfish on dive 2. The group however ran out of air very fast trying to get the shots. Last dive was at Ras Ghoslani to have a break and finally a session of split shot that was not very successful due to waves.

Bommie of Jolanda
Head On
Arrow head
Green Turtle take off
Videography

Day 6

Usually the last day is a more restful however we had 3 dives and one sunset split session so actually a full day. Here dive one was focussed on sunburst but ended up also being dive two.

Mushroom

Swarming
Hidden burst
Red
Red Sea Fan

Bommie at Ras Umm Sid
Buddy diving
Ras Katy Tip

Conclusion

It was a great trip although I am not sure I took my best shots in all cases. The Thistlegorm was under par while the dives at Ras Mohammed and other sites other than Shark Reef were better than expected.

One thing that proved to be absolutely right was that the ability to influence the boat schedule and itinerary is essential. We were in the water always first, Egyptian boat have a tendency to get in the water very late for dive one and this means most of the following dives have the sun really high and not always the best conditions.

Environmental Conditions joy and despair of the photographer

A few weeks ago I went diving in Swanage with BSOUP the British Society of Underwater Photographers that I have recently joined.

I was looking forward to some local diving so when I found out that they were organising a trip I managed to get on.

I drove there the night before and I was number two on the pier the next day.

It was a deceiving clear morning with perfect conditions on land.

I had two cameras one in the housing and one for land use so I took a few snaps.

Once parked on the pier I was informed by two friends that dive locally all the time that it was better to wait when the water level was a bit higher.

At that point it did look like a great day however there was a bit of wind.

I had my GH5M2 with the Panasonic 45mm macro that I acquired last year and has become my favourite macro lens.

I jumped in the water one of the first to find out the visibility was well maybe 1 meter? I could not see the LCD screen of the camera due to the suspended particles and had to use the viewfinder

One of the first things I say was this corkwing wrasse with a massive parasite near its eye.

Unfortunately I did not have a snoot or strobes suited for the challenge so I spend the first dive training myself on how to get the least amount of back scatter. Mind you when there are particles you will have backscatter not matter what you do.

Static subjects are ideal for testing so I had a go at some really simple stuff.

And again some anemone the object was to get the cleanest possible shot.

When I was reasonably happy I moved to some more interesting subject I gave up on blennies as I knew everyone would have shot some and besides my strobes were not the best for the situation and I found a cooperating cuttlefish.

I can tell you that to get this clean shot it took me quite a while but on reflection despite being very low I could not even see a hint of the surface so bad the conditions so I decided to get really close.

I wanted to emulate a profile of a person or perhaps an elephant not sure but I took a number of shots waiting for the tentacles to be in the right position and this is my best shot for the day.

I would say it is quite creepy but after all I had something decent and when I presented the shot in the club review at the sailing club it got some good feedback.

Now with that in mind let’s have a look at some shots taken in clearer water this is from Sorrento Peninsula.

Blenny Gold

You can see that clearer water improves contrast and sharpness as you would expect however as the UK shot was very close the gap is not as big.

And this is a shot from last time I was in the red sea

This is super macro so again suspended particles are not as important.

However if we look at a mid-range shot similar to the whole cuttelfish the situation is very different.

Here we are in Italy.

The Look

And finally here in the red sea.

Napo Lips

For as much as we may love our local dive site there is a degree of adaptation but also a restriction on the variety of shots we can take.

When I was working as resident dive instructor I remember the guidelines we were passed one was really funny and said:

“if the visibility is crap you don’t say that to the guests what you say is today we are going to focus on macro” then you make sure you choose a site where there is some.

I am looking forward to my boat in the Red Sea end of July remember if you follow me on instragram there may be some voucher codes to be used for discount.

If like me you have been trying to make the most of your local dive site you deserve to get yourself in clear water where you can actually see further away than your arm. Of course we do have some good days in England sometimes 5 even 8 meters but I tale Egypt and their 25+ meters any day of the week!

A closing thought on conditions and land photography, in fact even if visibility is not an issue most times unless you have fog, overcast days, excessively clear days do not make great land pictures either so we can say we are always on a quest chasing light and conditions.

Panasonic GH5M2 and GH6 HDMI Lag Optimisation

Key Facts

  • The camera live view is one frame behind due to the image processing pipeline, faster refresh rates reduce delays
  • HDMI latency does not depend on cable length
  • Most monitors have low latency
  • HDMI can carry audio and video and those need to be synchronised: if one of them is slower than the other a delay is introduced to match up
  • Resolution plays a role but not as important as others

GH5M2 and GH6 Lag between LCD and HDMI

  • The camera LCD has a resolution of 960×640 pixels and a refresh rate of 60 fps that can be reduced to 30 fps
  • When recording the camera shows the live view on the LCD with a delay of c 1 frame from real life
  • If you go into the menu HDMI Recording Output and set Sound Output  OFF you can see the real lag between the LCD and the HDMI
  • This lag is typically 2 frames from the LCD 
  • As frame  rate drops the lag increases
  • When the Sound is disabled the lag of the GH6 is generally better than the GH5M2
Measurements Results

Video Tutorial with my recommended settings

Items shown in this video

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2. Manfrotto 290 Xtra: https://amzn.to/3sSYggF

3. Manfrotto Light video head: https://amzn.to/3vTCHPc

4. Smallrig Monitor Mount: https://amzn.to/367f22z

5. Smallrig HDMI cable: https://amzn.to/3sVwNe9

6. Panasonic GH6: https://amzn.to/3HTUZlv

7. Panasonic 10-25mm 1.7: https://amzn.to/3KtxAcn

8. Atomos Ninja V: https://amzn.to/3MEKia0

HDMI Optimisation Wrap Up

  • Monitoring has acceptable delays from live time 50-150ms
  • Audio recording introduces a delay of 65ms on the GH5M2 and 35mm on the GH6 
  • The GH5M2 lag  of 190ms in 24p is too high and should be reduced to 160ms
  • There is a bug in the 30p mode on the GH6 as the lag is higher than 24p this needs to be corrected

Panasonic GH6 Power Solutions

The GH6 has the same USB power capabilities introduced in the GH5M2.

In this video I show you what I use with my cameras.

Initially with the GH5 I could only use a dummy battery kit and this will continue to work however it may have challenges with mechanical shutter or very high bitrate codecs of the GH6.

Therefore the recommended solution is a PD Power Bank

Pay attention to the checks you need to do as your power bank needs to deliver 9V 3A which usually means at least 45W better 65W

US

1. Dummy battery kit: https://amzn.to/3sFarxp

2. 65W PD Power Bank: https://amzn.to/35Kh6gW

3. Cheap USB Power Bank: https://amzn.to/3IVhM1u

4. USB C Cable: https://amzn.to/3tnsreQ

UK

1. Dummy battery kit: Currently Not Available

2. 65W PD Power Bank: https://amzn.to/3KgGfih

3. Cheap USB Power Bank: https://amzn.to/3HBGDGk

4. USB C Cable: https://amzn.to/3sGBmcj

Panasonic GH6 my preliminary key observations for Underwater use

I was able to have a 1 hour hands on session with Lumix yesterday and try some of the GH6 features.

Key points

  • Beautifully engineered machine
  • 1 stop dynamic range increase appears to be true
  • LCD design with tilt will make easier to see underwater
  • Records ProRes 422 HQ to CFExpress Card
  • Support HDMI 2.1 (playback only)
  • Battery same as the S5 and newer GH5M2
  • Battery consumption 25 to 35% higher in MP4
  • Significant HDMI lag if you use a recorder (1/4 of a second)
  • Will record to USB with a future firmware update
  • Will record prores raw externally with a future firmware update
  • No battery grip

I am going to do a longer write up once I have tested the camera for land wildife use however I have the following concerns

  1. What is the real battery life when you record ProRes to card instead of the low quality MP4, will it last at least one dive?
  2. HDMI lag is horrible just received confirmation that HDMI recording is capped at 4K resolution This proved to be a red herring as the lag is decreased from the GH5 series see here https://interceptor121.com/2022/03/10/panasonic-gh5m2-and-gh6-hdmi-lag-optimisation/
  3. The lag of the HDMI can be reduced if you use only a  monitor with a few tricks and it only needs HDMI 1.4
  4. The USB recording will be powered by the camera and the battery is already small

My recommendations for a professional grade housing would be:

  • Recording to card either 4K@60 or 5.7@30 depending on your use case
  • Optional monitor to run in 1080p to reduce lag HDMI 1.4 is sufficient
  • PD Power bank inside the housing so you are sure you will not run out for an entire day of shooting

For photography a classic housing would work but then who is going to get this just for photos?

Stay tuned for more information. If there is something you want to know about the camera use the comment feature here.

Choosing the appropriate gamma for your video project

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

Phone (HDR)9+
Computer Monitor10
Tv (1886 HDTV)11
HDR Tv13+
Projector16+
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).

Bit code mapping for 14 bits linear sensor data

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.

Camera TypeDRPDR (SNR=20)
Compact 12.99.8
MFT12.310.3
APSC1411.1
Full Frame1412.2
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.

Distribution of tones vs Gamma

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.

High Dynamic Range scene note the shape of the histogram with peaks on darks and lights
indoor scene with mostly midtones
Low contrast portrait despite the light background
Underwater landscape that does not have as much DR as you would think
Moth image predominant in midtones
Outdoor image with low dynamic range
Typical indoor party scene with flash does not have significant dynamic range
The same portrait with a cine gamma sees enhanced shadows and lighter overall image but with bright tones subdued

It may be useful to see the effect of LOG using the LUTs in photoshop on the raw data

Original image
Vlog image
Vlog + LUT back to Rec709

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.

Conclusion

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.

Announcing 121 with Nick More

Nick More will be answering my Q&A on a post next to be published on my blog.

Nick, is the British Underwater photographer of the year 2020 and has become a trademark of motion blur

Nick has recently authored a chapter on the latest edition of Martin Edge Underwater Photography and has provided me with some of his most exciting image including some that he consider special

Check his images on http://instagram.com/nicholasmoreuw and stay tuned the post will go up this Saturday June 13 2020

do you need raw video?

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.

Panasonic GH5 full resolution 20.9 MPixels DR

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 :

  1. RAW video unprocessed
  2. RAW video processed using Panasonic LOG
  3. RAW video processed using Canon LOG
  4. 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.

The same ProRes RAW files processed using log from Panasonic, Canon and Sony shows no visual difference

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.

Conclusion

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.

What is Dual Native ISO and does it matter to Underwater Video?

Dual native ISO is one of the most confusing topics in modern videography. Almost any professional camera Alexa, Varicam have dual native ISO. So what is it and does it matter to underwater shooters?

Sensitivity and ISO

Most of the confusion stems from the fact film no longer exists. When you had film you could choose different ASA or film sensitivities and once loaded in the camera you were stuck with it until it was finished.

With digital cameras having a memory storage you can flexibly change the ISO but there is some confusion about ISO and sensitivity so let’s have a look at some details.

Simplified digital camera schematic

In the schematic above the film represent the sensor. As with film the sensor has a fixed level of sensitivity that does not change.

The two triangles are gain circuits those will amplify the signal coming from the sensor that is still analog has yet to be converted into digital signal. A camera has typically a single gain circuit but some camera have two in this case we will have a dual gain circuit like the Panasonic GH5s or the Blackmagic Pocket Cinema Camera 4/6K.

Base or Native ISO?

When the gain circuit is set to 1 or passthrough an ISO measurement is taken according to ISO 12232 https://www.iso.org/standard/73758.html

It follows that as the amplifier is in pass through the camera can only have a single native ISO. So the whole definition of dual native ISO is incorrect and this should be called as Dual Gain camera as the sensor really has only 1 ISO. The ISO formula defines speed in lux*sec with the following formula this gives the native ISO of the sensor and then gain levels on the amplifier are mapped to an Ev or Stops scale.

It is worth noting that ISO values as seen on a camera are typically off and real values are lower, this is because manufacturers tend to leave headroom before clipping.

And how do I find out the native ISO of my camera? This is typically not defined clearly but generally is the lowest ISO you can set on the camera that is outside the extended range, where extended really means additional digital enhancement range.

For simplicity this is a snapshot of the GH5 manual where you can see that the native ISO is 200. The extended gain is below 200 and above 25600.

Panasonic GH5 manual

A method to check what gain circuitry is installed in the camera is to look at Read noise graphics from PhotonsforPhotos.

White dots map the extended ISO setting

When we look at a camera with a dual gain circuit the same graph has a different shape.

GH5s read noise shows the dual gain circuit, white dots are extended ISO

In the case of the Panasonic GH5s the sensor has a native ISO of 160, this is the value without any gain applied. You can also see that at ISO 800 when the high gain amplifier is active the read noise is as low as at ISO 320. This is why there is a common misconception that the GH5s native ISO is 800 but as we have seen it is not.

GH5s Manual

The GH5s manual mentions a dual native ISO setting, as we have seen this is actually an incorrect definition as the sensor has only 1 native ISO and this is 160.

The first low gain analog amplifier works from 160 to 800 ISO and the high gain amplifies works from 800 to 51200, values outside this range are only digital manipulation.

Gain and Dynamic Range

In order to understand dynamic range, defined as the Ev difference between the darkest and brightest part of the image, we can look at a DR chart.

Dynamic Range Plot for GH5s

This chart looks at photographic dynamic range (usable range) so it is much lower than the advertised 12 or 13 Ev from Panasonic but neverthless shows that dynamic range is always higher at the lowest ISO. This may or not be the native ISO, in the GH5s case is actually ISO 80 in the extended range. First of all is not possible to increase dynamic range by virtue of amplification so it is not true that the camera DR will be higher at say ISO 800. So why you find plenty of internet posts and video saying that the GH5s native ISO is 800? It is because of confusion between photo styles, gain and gamma curve.

Dual Native ISO VLOG Confusion

VLOG is a logarithmic gamma curve. https://en.wikipedia.org/wiki/Gamma_correction

When the gamma curve is logaritmics the camera will no longer reach saturation at the native ISO of 160 but will require an additional stop of light. This is explained in the manual where we can see that the values 160 and 800 have shifted to 320 and 1600.

A Standard Rec709 Photo Styles, E Vlog photo style

We can also see that when in variable frame rate the camera needs additional gain to record VLOG so the ranges are 320-2500 and 2500 25600. Values above 25600 are not implemented for VLOG because actually the camera has already at 51200.

So what has changed in the situation above are the base ISO of the Low and High gain setting depending on the gamma curve.

The compression of the gamma curve allows further dynamic range to be recorded despite higher noise due to a higher gain applied.

Comparison of Standard Styles and VLOG

From what we have seen before VLOG has higher dynamic range due to gamma curve compression compared to a standard photo style this has been measured by EBU. Full report here https://tech.ebu.ch/docs/tech/tech3335_s29.pdf

EBU DR Table

In terms of EV or stops HLG has more dynamic range than VLOG however is not grading ready and really is more an alternative to Like709. In this evaluation the knee function has not been activated so the real gap between HLG and Like709 is less than 4.3 Ev.

When it comes to VLOG vs CineLike D we can see that VLOG has a higher maximum exposure of cinelike D however in virtue of the additional gain applied also a higher minimum exposure resulting in 0.4 Ev less dynamic range. However what really matters is the maximum brightness as displays typically are not true black and a lot of the lower darks are just clipped.

Due to the difference of gamma curve and impact on ISO and the in variance of native ISO it is totally pointless to compare a linear style like CineLike with a log one (vlog) at same ISO setting. The comparison has to be done with VLOG set 1 stop higher ISO.

So most of the videos you see on YouTube comparing the two settings at same exposure settings are flawed and no conclusion should be drawn from there.

Because VLOG needs higher gain and higher gain means higher noise log footage in dark conditions may as well appear more grainy than linear photo styles. As VLOG really excels on highlights you need to evaluate case by case if it is worth using it or not for your project. In particular when the high gain amplifier is engaged it may make more sense to use CineLike D so that the gamma is not compressed and there are no additional artefacts due to the decompression of the dark tones.

Underwater Video Implications

When filming underwater we are not in situation of extreme brightness except specific cases and this is the reason why generally log profiles are not useful. However dual gain camera can be useful depending on the lens and port used.

In a macro situation generally we control light and therefore dual gain cameras do not offer an advantage.

For wide angle supported by artificial lights the case is marginally better and strongly depends on the optics used. If appropriate wet optics are used and aperture f-numbers are reasonably low the case for low gain cameras is not very high.

For ambient light wide angle on larger sensor cameras with dome ports dual gain cameras are mandatory to improve SNR and footage quality. This is even more true if colour correction filters are used and this is the reason a Varicam or Alexa with dual gain are a great option. However considering depth of field equivalence you need to assess case by case your situation. If you shoot systematically higher than ISO 800-1250 than a camera with dual gain is an absolute must even in MFT format.

Dark non tropical environments like kelp forest or Mediterranean are best fit for dual gain cameras

PANASONIC GH5 my underwater still rigs

The Panasonic GH5 is well known to be a great camera for video and I can confirm that see my latest videos

Clearly the camera is fantastic and with the right set up that I will cover in future posts it takes amazing video.

I wanted to start however from photography as the GH5 also takes great still images.

First and foremost macro. In general terms the lens choice of other micro four third also applies to the GH5 so my favourite lens is the Olympus 60mm. Alternatively if you don’t have that lens and you don’t have extremely small subjects you can get good results with a zoom lens I use the Pana 14/42 MKII but other work well too.

In terms of arms strobes nothing changes so my current rig is based on a Nauticam NA-GH5 housing and two Inon Z240. I have each arm set with 1x 8″ and 1x 5″ arm segments you will notice that the longer arms is closer to the camera this because in macro you will usually shoot above the sand so this makes it easier.

For wide angle the situation changes slightly as I use a 12″ arm segment as in the rig below.

GH5 with WWL-1 wet lens and 8+12 arm segments

For wide angle the arms return to a standard situation with shorter segment close to the housing. The same configuration applies if you shoot the 8mm fisheye.

In terms of floatation the GH5 housing is heavy with the 35 macro port is 720 grams and with the fisheye 620 grams. For macro I like my set up to be negative so less floats . For wide angle in case you take slow shutter speed shots I also use the tripod kit for the NA-GH5 this is not as good as a complete tripod but works well in wrecks

In the next posts I will talk about video as here there is a question about diopters and which ones do I use. Lights is also a topic of contention and will discuss few options there too

As always please ask questions if you wish