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
Ras Umm Sid
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.
The trip had a slow start at Temple followed by Ras Mohammed and some technical training on light at Beacon Rock.
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.
The dolphin came to play we had one hour with them swimming at speed around us and getting really close
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
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.
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 however I did produce a decent one with quite some fish.
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.
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.
After a few months of using the GH6 is time to answer the question pretty much every GH5 user is asking now.
The answer as always is … it depends. I hope this article will help you clarify your thinking.
I have done a number of tests on all the GH5 and GH6 series cameras including the original GH5, the GH5S, the GH5M2 and the GH6.
While many people talk about dynamic range most only care about noise and in particular if this will show in your footage or not.
Unfortunately read noise accurate calculation are only possible for RAW image files not video. Video has an additional issue which is temporal noise.
As noise is random by nature each frame will have its own noise and the changes in noise generate that flickering effect that everybody hates. This is called temporal noise and to an extent every camera has it.
Obviously if you have less noise you will see less flickering but all cameras will have some.
The other discussion that has been going on forever is that large pixels are better for low noise, this is also not true as more pixels can be added and noise averaged out. So the only thing that matters is sensor size, sensor construction and the sensor coating.
The original GH5 did not have a great coating so when the GH5M2 was released sharing the same coating of the G9 most people were saying well it won’t matter much while instead it does.
The benefit that the AR coating brings to the GH5M2 compared to the original GH5 is around 2/3 Stops which is not negligible.
The other difference among the various GH cameras is how VLOG is implemented.
In the GH5/GH5M2 VLOG is simply a curve and achieves no major benefit compared to other photo styles but it avoids you clipping highlights at expense of additional noise. This noise is managed overexposing 1 stop.
In the GH5s/GH6 VLOG applies underexposure behind the scenes of 1 and 1 1/3 stops so dynamic range is maximized. Both cameras have strategy to deal with noise. The GH5S applies noise filtering the GH6 scaling the net result is that VLOG in those camera is better than shooting something else.
Using a mix of read noise on RAW files and calculation of how noise is managed I have created the following chart that shows how noise goes at bit level when ISO goes up.
Here you can see all the cameras I think this graphic explains pretty much what happens at high ISO. For low ISO you need to take into account shot noise and my analysis is not able to evaluate that however this will make a small difference to the evaluations.
So lets go into the specifics
I am a hybrid user I want the best of both worlds which camera is better for me?
The GH5M2 is currently the best camera in this category, it offers the best still image performance, it has IBIS and video is very good and can be improved with an external recorder if you wish. It also records 8 bits which is fine for those who do not want 10 bits at all costs and uses SD cards. The dynamic range of a still image is the best of all GH series cameras as seen on photonstophotos. Remember that RAW files are not denoised or scaled like video.
I am a GH5 video user should I buy a GH6
Assuming that you shoot vlog because if you don’t any camera works just fine the answer is yes unless you are always at ISO 400 with your GH5 and do not want to buy more ND filter the GH6 is a significant step forward.
You need to evaluate however if you need all the GH6 offers.
I am a GH5S video user is the GH6 for me?
While the GH6 performance is better than the GH5S in the high ISO zone at low ISO is worse. The GH6 has IBIS and all the features the GH5S has however it is limited to 12800. The GH6 also produces 25 megapixels photos but as a GH5S user this was probably not important.
So the answer is yes if you don’t need really high ISO (>12800).
I am a GH5M2 video user is the GH6 for me?
If you don’t mind ND filters, use the camera in both daylight and low light and you need any of the features like 120fps 4k then the answer is yes.
The GH5 has been a very competitive camera and the GH5M2 further improved on it. The GH5S has its own niche and all of those are strong proposition. When looking at the GH6 the key criteria is that you are focused on video and that you need all the codecs and feature the camera has.
I have had the GH6 now for a bit more than one Month and it is time to get to conclusions in terms of the image quality in both photo and video.
In order to do that I have ran the GH6 side by side with the GH5M2 so far in my opinion the best hybrid Micro Four Thirds camera.
There have been a number of reviews online with regards to the GH6 video mode and for me two have stood out.
The first is the review from CineD and the second is from CVP
You do need to take into account a combination of factors when you look at video because the functionality and the camera image pipeline are what makes the video.
In general terms when it comes to functionality and codecs offered the GH6 is simply incredible. I have taken the opportunity to start bird video project and that would have not been possible with the GH5M2 or any previous GH series camera.
You can follow my work as it develops here
For the first time I am shooting in VLOG an entire project and this is due to the implementation in the GH6.
In the GH6 the implementation of VLOG is similar to what is done in the GH5s and the S series. So when you shoot in VLOG the camera is applying a negative adjustment of 1 1/3 stops behind the scenes.
This means when you are shooting at the 250 base ISO the camera is actually internally working at ISO 100.
In addition the GH6 no longer underexposed middle grey behind the scenes and it is spot on the grey card and in the RAW linear data.
In addition we now have a Dynamic Range Boost functionality that blends two frames one at High Gain and one at Low Gain to give you additional headroom in the highlights.
The result is that when you look at VLOG you have increased performance with dynamic range boost on from ISO 2000 and very strong dynamic range up to ISO 6400.
I have run some read noise tests using my astrophotography software and then applying the exposure shifts I come with the above result. Take into account that dynamic range in the GH5M2 is clipped on the highlights at 1 stop less so in reality although the graph seems to indicate that the GH5M2 at ISO 400 has more dynamic range this is not actually the case. However that is true is that up to ISO 1600 when the GH6 has dynamic range boost OFF the GH5M2 outperforms the GH6 in video.
I have shot side by side video and I will post on my YouTube channel some time soon.
However the first conclusion is:
if you do not need 4k120fps or 5.7k and don’t exceed ISO 1600 the GH5M2 is a better choice
What does this actually mean and how low light can you go? In practical terms f/2 1/60 ISO 1600 means 17 lux middle grey typical of floodlight buildings exteriors so not that dark but not that bright either. An indoor lounge with decent lights will have this level of illumination. Of course you can put a strong ND filter on the GH6 and enjoy more dynamic range however this has a number of other side effects.
The second conclusion is
Using dynamic range boost gives you 1 1/3 stops improvement on the GH5M2 from ISO 2000 and more highlight headroom but worse noise performance at low ISO
So what is the use case that will definitely favour the GH6? Typically need for high quality high frame rate formats and decent low light performance. The camera does pretty well up to ISO 6400 in VLOG.
If you don’t use VLOG there is noise reduction in camera so although it looks clean the details is not anymore there. So personally I would use VLOG when possible with the GH6.
When it comes to photos the design choices of the GH6 backfire. The camera has incredibly high levels of read noise as per this graphic.
In addition the read noise is higher in the low ISO before it turns to ISO 800 when dual gain output is in action.
This has of course a direct impact on the theoretical maximum dynamic range.
Here you can see that at values up to ISO 640 the GH5M2 really has an edge and the improvement of the GH6 is really limited to the region between 800 and 3200 the benefit is modest at best 0.5 stops.
So the third conclusion is:
If you are interested in the best photographic dynamic range in micro four thirds the GH5M2 (and the G9) are better choices
As an example those two images shot outdoor show that in effect our eyes do not really see read noise in a bright scene and once scaled the two camera cannot be taken apart. However if you had shot a long exposure at low ISO you will see grain with the GH6 under ISO 800.
For how hard I try I could not tell the difference between the two images above once processed and scaled.
Final disclosure all my figures look at pixel level noise and dynamic range. Scaling to a common size as shown by the image above will benefit the GH6 more as it has higher resolution but the difference is no so large that the data above is not valid so in general all I said above holds.
I have provided test files to Bill Claff of PhotonstoPhotos and he will publish more reliable and scientific results in due course.
We are both puzzled by the GH6 design and are waiting for another raw converter support to reconfirm however the triangulation of my data with other sources holds so I am quite confident of what I wrote here.
In 2018 I wrote the original article as I had acquired the GH5 and I was faced with a ton of non-sense on which format to use when I was shooting video. With the S series software stack Panasonic has made some changes to the options available and I thought it was about time to refresh the original article. As Before I will focus my analysis on 4K video and ignore other formats. This time I will be looking at the NTSC standard of 29.97 and 59.94 frames per second. This is simply because today majority of content produced by Panasonic consumer digital cameras is consumed online and all computer screen work at 60 Hz refresh rate so shooting anything different than 30 or 60 will result in choppy video. This presents some challenges if you are in a PAL zone and are shooting under artificial lights however for the purpose of this article I want to just ignore this issue, obviously you could shoot 24 fps and hope in a 24 – 30 conversion which is scatty of course. For simplicity I will refer to 30 and 60 fps and not exact values.
Today we have 5 settings for UHD
200 Mbps 420 10 Bits Long GOP 60 fps
150 Mbps 420 8 Bits Long GOP 60 fps
100 Mbps 420 8 Bits Long GOP 30 fps
150 Mbps 422 10 Bits Long GOP 30 fps
400 Mbps 422 10 Bits All-Intra 30 fps.
The last option is only available on the GH5 series and on the S1H. The first option is only available on the S series and the GH5M2.
Long GOP vs All Intra
The difference between Long GOP and All Intra is that in the Long GOP what is encoded is a group of pictures (GOP) and not separate individual pictures.
Within a Group of Pictures there are different type of frames:
I (Intra coded) frames containing a full picture
P (Predictive coded) frames containing motion interpolated picture based on a prediction from previous frames
B (bi-predictive coded) frames containing a prediction from previous or future frames
It is important to note that frames are not stored sequentially in a GOP and therefore the GOP needs to be decoded and the frames reordered to be played, this requires processing power.
The reason why H264/HEVC is very efficient is that within a group of picture there is only one full frame and the rest are predictions clearly if the prediction algorithm is accurate the level of perceived quality of long GOP is very high and similar to All-Intra clips.
This is the reason why comparing All Intra and Long Gop using static scenes or scenes with repetitive movement that can be predicted very accurately by the codec is a fundamental error.
So which format should you choose?
In order to understand the workings we need to dig deeper into the structure of the GOP but before doing so let’s evaluate the All-Intra codec.
AVC All-Intra explanation
This codec records at 400 Mbps so with 30 fps this means circa 13.4 Mbits per frame or 1.67 MB per frame and there is no motion interpolation so each frame is independent from the others. The implementation of All-Intra of the GH5 does not make use of CABAC entropy but only CAVLC coding is used, this makes the resulting files easier to read and to edit. The idea of All intra is that you don’t require powerful hardware to edit without conversion in an intermediate codec. However based on my experience this is not entirely through and you need a decent GPU to play it back and edit real time without issues.
If you consider a Jpeg image of your 3840×2160 frame on the GH5 you see that it stores around 4.8 MB per image because there is no chroma sub-sampling so if you wanted to have exactly the same result you would need to use ProRes 4444 to get a comparable quality (this not even taking into account that Jpeg are 8 bits images).
Video uses chroma sub-sampling so only part of the frame contain colours at a given time. Apple in their ProRes white paper declare that both ProRes 422 and 422 HQ are adequate to process 10 bit colour depth and 422 sub-sampling however they show some quality differences and different headroom for editing. If you count 50% for 4.2:0 sub-sampling and 67% for 422 you get around 2.34 MB and 3.5 MB frame sizes that correspond to ProRes 422 and ProRes 422 HQ individual frame sizes.
it would appear that All Intra 400 Mbps would fall short of Apple recommended bit-rate for 422 10 bit colour however practical tests show that AVC All intra at 400 Mbps is perceptually identical to ProRes 422 HQ and uses much less space. We also did some SNR measures time ago with the friend Paal Rasmussen and we did not find significant improvements shooting ProRes 422 HQ vs All-I on card.
Long GOP Codecs
Coming back to the other recording quality option we still need to evaluate how the various long GOP codecs compare relative to each other.
In order to fully understand a codec we need to decompose the GOP into the individual frames and evaluate the information recorded. If you look on Wikipedia it will tell you that P frames are approximately half the size of an I frame and B frame are 25%. I have analysed the Panasonic GH5M2 clips using ffprobe a component of ffmpeg that tells you what is exactly in each frame to see if this explains some of the people claims that there is no difference between the settings.
Link to Panasonic on the H264 implementation is here: documentation
There is unfortunately no documentation of the HEVC implementation that I have found to date.
200 Mbps 420 10 Bits Long GOP 60 fps Analysis
An analysis with ffprobe shows a GOP structure with N=30 and M=1 where N is the length in frames of the group of pictures and M is the distance between I or P frames.
This codec does not have B frames but only P frames.
Analysing a set of I frames of a fixed subject at 60 fps resulted in a frame size of 1.16MB for the I frames. This value is quite low however we need to understand that HEVC is much more efficient than H264.
I shot this test video time ago comparing the recording of this codec with a Ninja V in ProRes 422 HQ. As you can see no major differences however I have not pushed the grading in the clip.
The speed ramps in this video use this codec
150 Mbps 420 8 Bits Long GOP 60p Analysis
An analysis with ffprobe shows a GOP structure with N=30 and M=3 where N is the length in frames of the group of pictures and M is the distance between I or P frames.
So each Group of Pictures is made like this
IBBPBBPBBPBBPBBPBBPBBPBBPBBPBB before it repeats again.
Analysing a set of I frames of a fixed subject at 30 fps resulted in a frame size of 1.26MB for the I frames.
One very important aspect of the 150 Mbps codec is that as the GOP is double the length of the single frame rate 100 Mbps codec there are the same number of key frames per second and therefore it is NOT true that this codec is better at predicting motion however the additional frames result in better slow motion performance than what is done in software in majority of cases.
100 Mbps 420 8 Bits Long Gop 30 fps Analysis
An analysis with ffprobe shows a GOP structure with N=15 and M=3 where N is the length in frames of the group of pictures and M is the distance between I or P frames.
So each Group of Picture is made like this
IBBPBBPBBPBBPBBP before it repeats again.
Analysing a set of I frames of a fixed subject at 30 fps resulted in a frame size of 1.49MB for the I frames which is the highest if we exclude All I.
150Mbps 422 10 Bits Long Gop 30 fps
An analysis with ffprobe shows a GOP structure with N=15 and M=1 which means this codec does not use B frames but just I and P frames so the GOP structure is as follows:
IPPPPPPPPPPPPPP before it repeats again.
Analysing a set of I frames of a fixed subject at 30 fps resulted in a frame size of 1.25MB for the I frames.
H264 Codec Ranking for Static Image Quality UHD
So in terms of absolute image quality and not taking into account other factors the Panasonic GH5M2 and S series Movie recording settings ranked by codec quality are as follows:
400 Mbps 422 10 Bit All intra 30 fps (1.67 MB per frame)
100 Mbps 420 8 Bit Long Gop 30 fps (1.49 MB per frame)
150 Mbps 420 8 Bit Long Gop 60 fps (1.26 MB per frame)
150 Mbps 422 10 Bit Long Gop 30 fps (1.25 MB per frame)
The 100 Mbps and 400 Mbps codec are marginally different with the 150 Mbps long GOP really far away.
Note that as the technology is different I cannot directly compare the new 200 Mbps codec however based on visual impression and ability to grade I would recommend this over the 150 Mbps 420 8 bits
If you have a camera that has the 400 Mbps All Intra this remains the best format to use. V90 cards have dropped in price and are now available up to 256 GB. Unfortunately this option is only available on the GH5 series and on the S1H.
If you have a camera that does not have the All-I you can of course purchase an external recorder that in some cases will allow you to shoot RAW however this is not necessarily going to give better image quality and will definitely extend your processing time.
My revised advice, if your camera does not have the ALL I and you don’t have an external recorded, is as follows:
Use the 100 Mbps Long Gop codec it is very efficient in the compression and the perceived quality is very good. You need to get the exposure and white balance right in camera as the clips may not withstand extensive corrections. There is a risk with footage with a lot of motion of some errors in motion interpolation that can generate artefacts but this based on experience is not very high.
Use the new 200 Mbps HEVC for double frame rate it is not hard to process as HEVC 10 bits has hardware acceleration on all platforms.
Generally there appears to be no benefit using the internal 422 10 Bit codec nor the 420 8 bit double frame rate due to the limitations of the GOP structure, in addition the lack of hardware acceleration for H264 10 bits means you will need to convert the files for editing and they do not open with standard programs or load on phones or tablets. The same is true for All Intra but at least you can edit it ok.
To conclude this is a summary table with all key information
A certain number of GH5 users have upgraded to the S5, I was one of them until I sold the camera after 1 month of using and after buying a Ninja V. If you are a Panasonic S1/S5 user you need not only to contend with recording time limits but also with lack of codecs on the camera to fully use the potential that it has. You need to add an external recorder to really see the benefits because in real life situations you are not shooting a step chart so the dynamic range is destroyed by compression quality and errors and SNR drops. It would be interesting to test how does the GH5M2 400 Mbps compare with one of the S cameras using the 150 Mbps 10 bit codec but this is not something I did. I would only warn everyone going down that path that you may get less than what you think and you may require additional hardware to get there. Take also into account that S series only shoot 50/60 fps in APSC/Super35 mode and that in full frame mode there is a substantial amount of rolling shutter that makes pans and tilt practically not possible.
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.
If you have a GH5 (Mark I, II or S) you are probably not just doing underwater video but also taking scenes on land. In fact perhaps you are reading this blog and you do not even use your camera underwater.
Either way you know by now that shooting video just with your camera handheld is not a terribly good idea and the tools required are different from photography where once you have a tripod a remote shutter and a bunch of filters are practically set.
Video requires quite a bit of hardware. I have gone through this process and even tried to adapt some of my underwater hardware but it was really bulky and at the end you are better off with proper gear so I use Smallrig.
Smallrig is a Chinese company that makes tons of various bits for your camera for a variety of situations. The first item you need is a cage and they have just released a new updated version for the GH5 cameras.
Clicking the image above will take you to Amazon UK where you can check details of the item.
The cage is the starting point and you can put your camera strap the weight of 190 grams does not add terribly to the camera and in any case if you have a GH5 you are used to carry some more weight. The cage lives permanently on my GH5 unless I put it in the underwater housing.
I am now going to go through a series of set up that I use with some other components as well but first some words of warning.
Smallrig suggests to use a Nato handle on the left hand side however this blocks the HDMI side port from opening. In addition the arri locating pins are too high and if you use a side handle in arri format it will hang and not be level with the cage.
I wrote Smallrig to tell them and they accepted the feedback the reality is that they do not test designs with camera they run 3D simulations and they do not go and open all the ports, plugs etc. So the only handles that actually work with this cage and do not impede any functionality are in this article.
Monopod/Tripod Rig for Wildlife shooting
The basic rig for monopod and handheld work (this means you hold the camera steady and you do not move) has a top handle and a side handle plus a small microphone and if required an LCD shade.
I have gone through a series of handles for this cage and I have settled for the following items:
We are looking at £180 for all this hardware this stuff is not cheap however I just can’t emphasize how more ergonomic and effective this is compared to holding the camera directly.
I have this rig used it for my deer film project.
There are situations where setting up a gimbal is too much and you want to take simple footage handheld just using the camera IBIS. This works very well with a standard zoom lens like the Panasonic DG Leica 12-60mm or the Lumix 12-60mm.
In those situations is better to have two handles and the set up needs to be as light as possible.
You will notice that the handles are smaller and they are also lighter. If you walk with your camera you are typically using the LCD and with two handles you are able to be much more steady if you were just gripping the camera.
You can also use the EVF instead of the LCD if you prefer to have three points of contact with the camera.
In those situation where you are in a studio or controlled environment you can use manual focus for pulling and usually you also have a monitor to have precise exposure. I tend to use this on a fluid video head and sturdy tripod for indoor shots.
Here I am shooting the mighty PanaLeica 10-25mm and I have my trusted Swit CM-55c field monitor.
I have an atomos ninja however since the GH5M2 has 60 fps in camera at 10 bits I only use it in bright outdoor scenes and the SWIT is just better in terms of tools and lighter.
With the new linear focus option for manual focus you can have a complete 360 degree turn of the wheel for manual focus if you so wish or shorter runs if preferred. I use 300 degrees.
It can be a bit daunting to search for the right items that do the job when you want to use your cage I hope this article will help you making the right choices and save time without having to do the trial error and return process I have done in the last year!
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.