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.
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.
And finally here in the red sea.
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.
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.
I hope you found the tests useful and I guess the key question is:
Is the GH5S still worth it in 2022?
I have prepared a comparison table with the GH5 and GH5M2 using data available and for noise my subjective measurements supported by the video evidence.
As you can see from the table the GH5S still has some unique features:
RAW support (ProRes RAW and BRAW)
High ISO performance straight out of camera
Slightly lighter and better battery life
So if any of the above are essential to you there is still a case for the GH5S.
However the GH5M2 with Neat Video will cost you $1,699+$129=$1,828, for sure you will have to work without Vlog and RAW but you will have many other benefits and you will not need a recorder to shoot 50/60 fps bringing the overall cost down significantly.
For part 3 of my test I ran the GH5S side by side with GH5M2 with the same settings used for daylight. The GH5S used VLOG which is the best photo style for it while the GH5M2 used CineD2, again the best photo style for it. Bear in mind if you had run this comparison with both cameras on VLOG the GH5S would have trashed the GH5M2 at high ISO because the implementation of VLOG in the GH5M2 is simply not performing.
The two cameras were set in multi metering with focus at hyperfocal distance. I tried to match the field of view using the 10-25mm on the GH5M2, make no mistake the PL 15/1.7 I used on the GH5S is an amazing and very sharp lens. Both cameras were set to auto white balance and I put the GH5M2 in auto ISO because it shows on screen the value it is using while the GH5S was set in complete manual. Whenever the GH5S was displaying a negative value on the meter I would increase ISO 1/3 Ev. The GH5M2 was left to deal with it in auto as I had previously confirmed the meters were aligned, or at least this is what I thought until this test.
I started all the way from ISO 200 and waited until night fall.
If you want to watch the video and form your own view here is the link. You will need a Tv with zoom function to be able to see the fine details.
My expectation was that the cameras would perform almost the same until ISO 1600 at that point the dual gain of the GH5S should produce better results. I will spare the analysis at lower ISO values as it does not really say much.
As explained in the video you need to focus on three part of the image. The top part and any residual tone of the sky tells you if the camera is loosing DR. The tables at the bottom are a sign of loss of detail due to noise but also of possible temporal noise reduction. Temporal noise is a flickering resulting from noise scattered differently in the frames. When the image retains detail but has this flicker it is said to have temporal noise. If the clip looks stable but lacking a bit of edge details it is a sign of potential temporal noise reduction in camera.
Due to the lower pixel count temporal noise reduction in the GH5S would perform better than in a higher pixel count camera.
Here the GH5S is in low gain and my expectation was performance to be very similar. At this ISO value the GH5S retained good detail however showed more noise in each part of the frame.
The noise levels appear identical in the static parts of the frame.
All in all at ISO 1250 the situation appears very similar the GH5S has a bit more noise but still have detail compared to the GH5M2.
The light dropped suddenly so I did not manage to record the ISO 1600 step on both camera at the same time as I was distracted by external factors (had to order at the bar).
Although the noise appear similar I would say the GH5S retained more detail at ISO 2000, consider the observation is far away and on the edges of the frame so it is a difficult scenario.
Looking at the static part gives a different picture with the GH5M2 having an edge and the GH5S smudging details.
I was expecting the GH5S to be a clear winner at its second native ISO.
The part of the frame with motion did not show a much better detail for the GH5S while the static part looked cleaner.
This behaviour makes me think that the GH5S has a stronger temporal noise reduction filter. When it does not detect motion it goes down hard resulting in a very clean image. When it does detect movement it becomes more cautious especially if the moving parts use only a small area. This would explain the mixed behaviour in the ISO 2500 situation.
Overall I was expecting much better performance and a clear difference between the two.
My expectation was that as the ISO was going up the gap between the two cameras would have increased however at ISO 3200 I was surprised to see the GH5M2 made a recovery and the quality is almost identical.
In addition I can see the GH5S noise reduction starting to eliminate some details when it can’t quite work out what to do. Look at the table tops near the two walkers in the frame.
At this point I was presented an additional surprise the two camera started to have a gap in the metering so for a good few minutes the GH5M2 stayed on ISO 3200 while the GH5S was reaching out for more gain.
Ultimately this resulted in identical image quality in the parts with motion with the GH5S retaining some fine details better but the GH5M2 producing at the end a comparable result.
I won’t bore you with the static parts as they look identical.
The GH5M2 reached ISO 4000 however the GH5S had already moved to 5000. The consequence is that the image quality was the same.
Again the static parts were the same.
Eventually both cameras were at ISO 5000 and here I could see a lead of the GH5S in the motion details but no benefit in the static details in terms of sharpness. However when you actually play the footage you can see the flickering of the temporal noise on the GH5M2.
The static details retain the same definition and resolution.
At this point is very clear to me that what is giving an edge up to now to the GH5S is the superior performance of noise reduction in camera as the actual dynamic range did not seem to be an element. If at all the sky becomes washed out sooner in the GH5S.
From this point onwards the GH5S takes the lead however I would not say that the resulting image quality was very high. I would frankly avoid this ISO level but in desperate cases can certainly be used.
Perhaps more interestingly the GH5M2 although more noisy seems to preserver more details of the static part.
It became apparent during this test and you will see it clearly in the video that the GH5S has a very effective in camera noise reduction (even with NR=-5 this is still on) potentially because it does not have many pixels and can be quite aggressive with it. I tried using Neat Video with the GH5S however there was loss of detail, with the GH5M2 I could apply a temporal filter to the ISO 5000 you can see the results in the video and see what you think.
I was surprised to see the camera meter reading differently considering the matched set up. I also could see that the light level had to fall considerably so that the GH5S would have a benefit. In substance until both cameras were at ISO 5000 (I was using f/1.7 lenses) it did not look like the higher sensitivity of the GH5S was sufficient on its own to give a performance edge.
I continued the test all the way to ISO 25600 for the GH5S the results were not exciting although you could say the camera does a decent job at showing some information. In general it seemed the camera was running out of dynamic range and also of image quality.
At this point (ISO 12800) I would say that the benefit of the GH5S was now a full stop. In addition it can go to 25600.
Low Light Sensitivity
I was expecting to see a material difference between the GH5S and the GH5M2 from ISO 1600 or at latest ISO 2500 with this gap growing at higher values. What I have seen instead is a bizarre progression where the GH5M2 would catch up and almost match the GH5S until ISO 4000 with a clear benefit only when the exposure was 5000 for both. It looks like in line with the aptina Dr Pix paper benefits only arrive near 0.01 lux*sec becoming higher later.
So we need 50% of ambient light * exposure time / aperture stop to be 0.01.
If we think about it f/2 1/60 this means aperture in stop is 2 which means a factor of 4. So working the inverse in order to get 0.01 lux*sec we would have 2*60*4*0.01=4.8 Lux.
If we consider an f/1/7 lens than this becomes 3.4 Lux and finally with an f/1.4 lens this would be 2.4 Lux.
In reality most f/1.4 or f/1.7 lenses really are just f/1.8 or f/2 so a value of 4 Lux for ambient light is reasonable. And this is the point where the benefit would start getting better as it goes darker. This is also consistent with my test the real performance difference started really to manifest a lot at ISO 5000 and became higher later.
We also have to consider thought that certain part of the image like the deep shadows will show a benefit sooner even if the ambient light is broadly sufficient. So it is not as clear cut as it would appear and the test confirmed such behaviours.
Perhaps the biggest surprise was how effective a traditional front illuminated sensor can be and how small was the gap with the GH5M2.
A key difference between my tests and others you can find on the net is that nobody actually runs tests with two cameras side by side and we have seen that at high ISO values the cameras did not meter exactly the same but what matters is the image quality at that point in time so the test still stands.
One thing has to be said though and this is that as of today if you want a micro four thirds camera style device (not a box or a cinema camera with no weather sealing) that works in low light with VLOG you are left with only one choice and that is the GH5S.
In the next part a wrap and some considerations about use cases and current competition for the GH5S.
The second part of the test consisted in running the GH5S in parallel to the GH5M2 using CineD2. If you wonder why I did not use VLOG on the GH5M2 is because as discussed in a previous article VLOG on the GH5/GH5M2 is just a picture profile and does not really do anything other than deteriorate the noise in the shadows. So I used CineD2 as I wanted the maximum performance out of the GH5M2. The GH5S instead performs better in VLOG for reasons explained in the VLOG article as well.
So with the two cameras on tripods I went out for a walk and took several shots with similar exposure settings. Instead of using ISO 400 I used 200 on the GH5M2 which means the lens was one stop brighter on the GH5M2.
The practical tests confirmed what I was expecting based on the light box tests:
The GH5S has a tendency to oversaturated reds and move blue to cyan so deep blues in the sky are almost never available. This was not so much of an issue during this test as the sky was overcast however you can see the clouds do not really have any blue tones.
Auto white balance during the day performed consistently to the GH5M2 generating most times the same reading or at most a 200K difference. On this basis I do not understand why users speak about a magenta cast in some shots.
The GH5S had better battery performance of the GH5M2 and I think this has to do with the LCD which is now much dimmer than the new camera as you can see in the picture.
I did not see any more dynamic range in the GH5S. I would say a tad less than the GH5M2 on CineD2 at base ISO. This is visible in the second scene where I spot metered on the subject. Both camera had almost no tones left in the sky although they did not clip with the GH5M2 having perhaps an edge there.
Looking at the waveform after ETTR with the cameras showing near clipping you can see that the highlights are practically the same however VLOG has lower midtones and less darks.
This is the full video on youtube so you can make your own calls. The footage has been stretched to maximise DR ad hoc in the first scene and hues have been corrected for daylight. No other grading has been performed. In the second scene both cameras were maxed out and no further stretching has been done as it was not improving the scene.
The potential benefit of the GH5S over other models
The following table extrapolates the GH5S dynamic range considering a shift of 3dB in gain (ISO 400 -> 200 shifted)
Delta GH5M2 Max
Delta GH5 Max
PDR table with gain shit
Please note this is an extrapolation I have not take measures however assuming VLOG impacts all cameras equally once gain is taken into account what you see there is that the GH5S has a potential benefit between 0.76 and 1.46 Ev over the original GH5 which is consistent with user experiences and website tests.
When you look at the GH5M2 the potential benefit drops to 0.5 and under 1600 is almost zero becoming 2/3 Ev when the GH5S is in high gain. This is also consistent to various tests on websites like dpreview and CineD.
The table does not consider however that CineD2 on the GH5M2 does accomplish more than VLOG in virtue of less noise and also does not consider the fact that some of the DR will be lost in the underexposure happening behind the scenes.
Part 2 Wrap Up
It is not difficult to see that the GH5S has good performance in daylight conditions however it does not really have any edge worth investing in it for this use case. So if you are not always at high ISO levels (>>1600) you may be getting better value from the GH5M2 that costs less takes photos and has IBIS. To be perfectly honest due to the way VLOG works I did not see major benefit even when I tested the S5 because the extra DR in the highlight was not really useful.
When we look at the GH5 instead the GH5S does remain superior but this is due to weakness of the GH5 itself. It really is quite clear that the software stack of the GH5 is really dated and the camera fairly noisy.
In the next article I will analyse two side by side shots of the GH5S and GH5M2 in low light.
Since its announcement exactly 4 years ago the GH5S has been an enigmatic and successful camera for Panasonic. Today 4 January 2022 it still retails at £1,899 and it has upheld price more than the original GH5.
You would wonder who would want to get a 10 megapixel camera without stabilisation and the answer is many people that are solely focussed on video. The camera has built a reputation for low light performance and dynamic range and has been praised for its ‘color science if there is such a thing.
So after using the GH5M2 for six months I decided to rent a unit from Wex Photo and run a side by side comparison for myself.
When I say side by side I do not mean just in theory I mean in practical with the cameras close to each other and shooting the same scene.
For my tests I used a light box and a set of grey, white and color checkers and the same identical lens Panasonic 30mm macro. And for the outdoor scenes I set the GH5s with a Panasonic Leica 15mm 1.7 and the GH5M2 with a 10-25mm. As the GH5S has a multi-aspect sensor I needed to zoom the lens to less than 14mm to get the same field of view.
Before getting into the actual tests it is time to debunk a few myths about the GH5s.
Less Pixels = Less Rolling Shutter not more Dynamic Range
Camera readout is limited mostly by the speed of the Analog to Digital conversion. So having less pixels helps readout and reduces rolling shutter. This is the reason why all camcorder and dedicated cinema cameras have the minimum amount of pixels required and nothing extra.
This is true for the GH5S, the reputable website CineD as well as dpreview show a benefit of a couple of milliseconds for the GH5S over other cameras with a 20 megapixels micro four third sensor. This may be important when doing panning shots or using the camera on a dashboard or gimbal.
On the bigger pixels helping dynamic range there are a number of sources that explain why this is not the case but more importantly the the GH5S sensor has actually a quad bayer structure with cells of 4.6 microns made of 4 pixels each. So in reality the GH5S sensor has 43.64 megapixels arranged in 10.91 million cells that give 10.91 megapixels in 4:3 aspect ratio 9.07 megapixels in the 17:9 wide format. So not only bigger pixels are no help to dynamic range but the GH5S sensor actually has more pixels.
The sensor in the GH5S does not have higher dynamic range than other MFT cameras
Photonstophotos managed by Bill Claff is the only site that has measures of almost all camera models. While engineering dynamic range is purely determined by the difference between saturation signal and lowest readable signal, photographic dynamic range is what we see and is generally determined from setting a defined SNR for the image scaled to 12″ size long or 8 megapixels. This is roughly the 4K video resolution so it is a good starting point.
From this graph we can see that the G9, although based on the same sensor of the original GH5, outperforms the latter and the GH5s when it comes to dynamic range.
I am always cautious with measures taken by others so I did a full test and asked Bill to check the difference.
While in some cases there was an improvement of 0.18 Ev this would not be sufficient to push this sensor above the G9.
So the Panasonic GH5S sensor does NOT have more dynamic range of other Panasonic cameras with more pixels on the same format although it does quite well and at high ISO outperforms the GH5 at RAW level.
The multi aspect sensor has a bigger size in video but this does not improve dynamic range significantly
Due to the multi aspect ratio it is true that the sensor does not loose from a crop when changing aspect however we need to understand more what the potential benefit is.
A higher megapixel sensor with pixel of 3.3 microns will use its whole width and a cropped part of the height. If we look at 5184×2916 pixels surface this measures (5184×3.3)x(2916×3.3)=164.62 square millimeters. The GH5S with a cell size of 4.6 microns will have a surface of (3840×4.6)x(2160×4.6)=175.5 square millimeters.
Considering that dynamic range is proportional to the square root of the surface the improvement would be SQRT(175.5/164.62)=1.032 which in Stops is 0.046. So the larger area does not really do anything in 16:9 aspect ration.
In 17:9 the situation is a bit different and this benefit is 0.14 Ev still nothing so large to have a very significant impact.
During my tests I found the change of horizontal field of view which is what really matters confusing so personally I like to have a standard sensor with crop considering the benefits of multi-aspect are really limited.
The sensor of the GH5S has higher sensitivity
One of the features that the GH5S has is the so called Dual Native ISO. This is a marketing term for the Aptina DR-PIX technology which has been implemented by Sony for some time.
A white paper is here as you can read the technology enables sensors to increase sensitivity at the expense of dynamic range. The potential improvement is up to 5 dB however this is only true for very low light levels. To give an idea at deep twilight there is around 1 lux so with an exposure time of 1/50 of a second we have 0.02 lux*s this is not in the core range for this technology so more is required.
Back illuminated sensor give the additional sensitivity required as explained on Sony semiconductors page.
Now the combination of dual gain and back illumination means that the GH5S can do better at low light levels but also can tolerate very high levels of ISO. So the GH5S has additional high ISO capability for around two stops which means you can almost shoot in the dark. The key question is when does this matter when you have a fast lens.
Looking at an exposure waterfall calculator we can see that with an f/1.4 lens at 1/60 and ISO 3200 we can still cover twilight which is when public illumination is switched on.
In general terms all being equal the GH5S would have around 2/3 stops benefits in low light or in deep shadows compared to other cameras with MFT sensor.
This is quite interesting to test and quite simple using a color checker and a noise reduction software like neat video.
Here the first two samples are grey and black patches in VLOG at ISO 1600 using the Low Gain setting.
We can see that while the noise level on the middle grey is contained the black patch jumps to 4.4.
If we take the same reading manually selecting the High Gain range we can see how the situation changes.
On the middle grey we are in a very similar situation. However when we look now at the black patch we can see that the level of noise has dropped significantly.
So we can see that switching the camera from low to high gain at the same ISO has a significant benefit on darks in terms of noise.
VLOG to the rescue
With what we have said so far there has not been enough to substantiate why the GH5S would have more video dynamic range than the GH5 but VLOG comes to the rescue.
When Panasonic introduced the Varicam 35 in 2014 they were presented with the issue of having too much dynamic range.
Panasonic already have their CineLike Gamma that was able to manage 12 stops of dynamic range however this was no longer sufficient.
So the Varicam35 was provided with RAW output and with AVC Intra recording on their expensive expressp2 cards. VLOG provided an opportunity to compress the camera dynamic range in a 10 bit container that could then be recorded on card.
Panasonic made a first attempt to deliver VLOG to their Lumix with the GH4 however at 8 bit depth it did not work well. The GH5 is the first camera to have a 10 bit implementation however due to the smaller sensor it was limited to a smaller range called VLOG L which covers 12 stops of dynamic range.
A report by EBU indicates that the GH5S has more dynamic range in both CinelikeD and HLG modes compared to VLOG. Those are not scientific but are a suggestion that perhaps for a sensor with a maximum dynamic range around 12 stops VLOG is not the most efficient option. HLG presents challenges due to the color space and gamut differences however CineLike D does not require anything specific to process. Users have complained about the color accuracy of CinelikeD and generally Panasonic has been sponsoring VLOG and so have many websites under the assumption that this was the best way to preserve the full dynamic range.
While this may be true for larger sensors it would appear that this is not definitely true for the smaller MFT format.
In addition the implementation of VLOG among different camera is not the same as I already wrote here.
So in summary it is true that if you want to use VLOG the GH5S is a better option with a benefit that can be around 1 stop at high ISO over the best performing MFT camera at time of writing the GH5M2.
If you want to see the behaviour of the GH5S using a color checker you can appreciate the low level of noise at high ISO.
Color Accuracy and White Balance
I used a vectorscope to evaluate how the GH5S reproduces hues in VLOG. All tests done with factory settings and official Panasonic VLOG
You can see that the skin tone marker is exactly on target however red is more saturated than other colors and cyan is desaturated
The blue use is also shifted towards cyan.
This means that the GH5S can potentially produce a red cast and not give deep blue skies.
The weather was rubbish during my tests however from this example you can see how the red is definitely overboard by looking at the hat of the runner that comes on the scene.
This is something to watch out and a hue correction in post is required in most cases to bring things to normal.
Note that this issue with VLOG and the oversaturated red is also present in the GH5M2 that has very much the same color science or lack of thereof and will produce reddish tones on your skin that need to be corrected.
Take into account that hue correction is not resolved by setting a custom white balance.
For the hardcore pixel peepers I have shot a whole sequence of xrite color checker at all ISO steps
On a positive note the GH5S in VLOG meters correctly unlike the other GH5 siblings that are 1 stop overexposed.
You can see on the waveform monitor that setting the target at zero gives middle grey exactly on 50% on multi metering. On spot it will go at 45% which is what is expected.
Part 1 Wrap Up
From a series of quite simple tests done in a light box my expectation is that the GH5S will do ok but not sensationally in bright scenes and will do better in low light low dynamic range scenes.
In the next article I will analyse two side by side shots of the GH5S and GH5M2 in daylight.
Although COVID-19 vaccinations are starting to make a difference and travel is resuming is fair to say that we are still far from where we were in 2019 and it may take some time to get back there.
This means our diving travel destinations have been changing and there is much more local diving than before. Big countries like the US have a lot of diving and Caribbean destination on their doorstep those travellers have still quite a lot to choose in comparison to others.
For Europeans, in the geographical sense, there are options for short haul travel. Those do not compare to your macro trip to South East Asia or pelagic trips to South America or Maldives or similar, however you can get some pretty good shots.
In 2020 I had my first experience in Massa Lubrense and this year I was back there.
I wrote about it last year if you are looking for more details on the logistics so in this post I will focus on photography.
Getting back into RIB diving
After 1 year of forced stop from boat diving getting back into a RIB diving with 15 liters steel tanks was a bit of a shock, certainly better than shore diving but yet not exactly streamlines especially as I decided to get a semi-dry suit. Due to stock shortages in UK I was only able to fit into a Scubapro Nova Scotia 7.5mm that has a lot of buoyancy. The suit was definitely toasty but required a lot of weight to go down as it was brand new. Temperatures range from 26 degrees at the surface to 17 at depth in certain sites so after a chilling experience last year this time I was definitely ok.
I did 2 sets of 3 days diving clocking a total of 16 dives. The dives were all close to 60 minutes (time to get back on the RIB by procedure) and depth of 33 meters. I have to say I avoid decompression dives but really this destination does require you to dive deeper than what you expect in tropical destinations.
I had the new Panasonic GH5 Mark II that fits in the housing of the Mark I and two Sea and Sea YS-D2 strobes. I took only two lenses the Canon 8-15mm fisheye with metabones smart adapter and the new (for me) Panasonic 45mm 2.8 macro.
The visibility can be an issue on the Italian coast however you can mitigate the issue with good technique and photoshop. Interestingly water is always clearer at depth where of course you lack light so strobe power is important to get a good shot.
Banco di Santa Croce is the best spot to meet large grouper and has many sea fans and also macro life, eagle rays and other things to be found.
I find also very interesting the schooling fish even if this is usually not well behaved Barracuda who never spin around or a variety of sea bream
For me the most interesting wide angle though are the cave shots at Scoglio dell’Isca and Punta Campanella
Sunburst opportunities are abundant and due to the depth relatively easy scorpionfish or small sea fans are ideal.
The performance of the Canon 8-15mm on micro four thirds is just legendary!
Close Up and Macro
Afternoon dives at Puolo but also dives in Santa Croce or Mitigliano offer lots of close up opportunities.
It was the time of testing the Panasonic 45mm 2.8 on land I had the impression it gave better rendering of the Olympus 60mm and I definitely prefer it underwater.
It is not just macro a long lens gets interesting closeup of large groupers
Diving in Italy delivered again. I am seriously thinking a group trip would be worth it next year based on the itinerary I sketched last year.
Dates for 2022 would be 4-11 September outside of school holidays the diving is really calm as most Italian divers are back to work and the conditions are usually superb. If you are interested leave a comment and I will come back to you with costs and planned itinerary.
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.