Jump to content
Don Kotlos

Why recording LOG with an 8bit codec is most probably going to get you in trouble.

Recommended Posts

I believe most of you know this but for the ones that are not  that keen with the idea let me explain.

The last few months I see a great deal of enthusiasm for LOG profiles.  I also see a lot of people complaining about colors when trying to grade these profiles whereas specific cameras such as the Canon 1Dc can give great results.

As Andrew has mentioned many times there is a great deal of effort put into customizing not only the colors (how signals from the RGB sensors are combined) but also the LOG profile to a specific camera. It is similar to the effort that camera companies put into their JPEG algorithms for stills.  For example you have companies such as Fuji  that have great experience with color and can provide very usable JPEG profiles.  That is not always the case with other companies.

Now when shooting RAW (>12bits/channel) you can most probably get any color you want. Yes it will require quite a bit of effort but you can do it given infinite amount of time. Of course time is limited, as is space - recording space. Here comes the 8bits/channel (and reduced color sampling). 

Everyone knows that when shooting with a LOG curve you map a greater range of input values to the image.  In such cases skin tones are mapped into a tiny fracture of the color spectrum. To give you an example the variation of skin typical pixel intensities in RGB space (to make things easier) is usually +/-10 for each channel:  20x20x20 --> 8000 colors. In this space you have to accurately map the tones of the skin. Yeah right.

**PERSONAL OPINION**  The most grades that I see with A7s & GH4 log profiles end up with plastic skin colors. I wonder why...

 Kudos to Canon.

Do yourself a favor when you are using any log profile and record with a 10 bit codec.

Here is a great article that dives a bit more into it:

http://www.newsshooter.com/2015/07/27/looks-picture-profiles-luts-and-log-why-when-and-how-you-should-use-them/

P.S.

I am not an engineer and neither I am a professional videographer so I could very well be totally wrong about all this. But I am just fed up with the boxing match  threads between different cameras. Let's move on.  

Share this post


Link to post
Share on other sites
EOSHD Pro Color for Sony cameras EOSHD Pro LOG for Sony CamerasEOSHD C-LOG and Film Profiles for All Canon DSLRs

I am not an engineer and neither I am a professional videographer so I could very well be totally wrong about all this. But I am just fed up with the boxing match  threads between different cameras. Let's move on.  

Where is your area of expertise, then? Not an attack--honestly curious. 

Totally agree with the post, though. Why everyone isn't using the GH4's 10-bit out is beyond me. 

Also, how many times have you read this exact conversation:

"I can't get great colors with X-LOG!"
"Yeah, you'll have to learn more about color grading to get the most out of a LOG profile."
"But that's so much work! I'm a filmmaker, not a colorist. Isn't there an easier way?"
"Well, you could always buy some LUTs and let professional colorists do the work for you."
"LUTs are too expensive! I want something I can grade myself!"
"Um...how about just not using LOG? Your camera has lots of other color profiles that are easy to handle."

"Then I won't get the best DR the sensor can give me! What kind of noob doesn't use LOG!?"
-_-

Share this post


Link to post
Share on other sites

[..]


"I can't get great colors with X-LOG!"
"Yeah, you'll have to learn more about color grading to get the most out of a LOG profile."
"But that's so much work! I'm a filmmaker, not a colorist. Isn't there an easier way?"
"Well, you could always buy some LUTs and let professional colorists do the work for you."
"LUTs are too expensive! I want something I can grade myself!"
"Um...how about just not using LOG? Your camera has lots of other color profiles that are easy to handle."

"Then I won't get the best DR the sensor can give me! What kind of noob doesn't use LOG!?"
-_-

:)!

Share this post


Link to post
Share on other sites

 

**PERSONAL OPINION**  The most grades that I see with A7s & GH4 log profiles end up with plastic skin colors. I wonder why...

My personal opinion: most people are crap at grading.

This became evident when Magic Lantern RAW gave everyone the possibility to pull off extreme grades with the raw files... this resulted in a lot of terrible grades. Same happens with the LOG footage from the A7S and GH4.

I think this is a a bigger issue than 8 bit vs 10 bit.

Share this post


Link to post
Share on other sites

My personal opinion: most people are crap at grading.

This became evident when Magic Lantern RAW gave everyone the possibility to pull off extreme grades with the raw files... this resulted in a lot of terrible grades. Same happens with the LOG footage from the A7S and GH4.

I think this is a a bigger issue than 8 bit vs 10 bit.

Not to mention that most people are not only unwilling to learn grading, but downright offended when you suggest that maybe their grade is the problem. A problem that affects 80% of us--not being colorists--is impossible to acknowledge without pissing people off. Isn't that insane

Some flat/log profiles, like C-Log (faux-log designed for 8-bit), Nikon's FLAT profile (not true log), and V-LOG L (I don't really know why) respond perfectly to nothing but an S-curve in post, but they're by far the minority cases and you're still thinning out your skin tones.

People realized a while back that 10-bit ProRes (Blackmagic) and 12/14 bit RAW (Blackmagic and ML) held the key to great image quality, then 75% of us promptly forgot the second 4K hit the affordable market. The other 25% are blessed with an amazing gift: the power to remember things

Share this post


Link to post
Share on other sites

Where is your area of expertise, then? Not an attack--honestly curious.

Neuroscientist, studying how we (our brain) processes visual input. 

My personal opinion: most people are crap at grading.

Could be true too. 

In the following video (hope Andrew does not block it :p)  they used two cameras FS7 and A7s. Can you guess which images come from which camera? Hint: compare 1:43 to 1:44. 

https://vimeo.com/134440445

Share this post


Link to post
Share on other sites

Sooo.. I have very little experience grading. Tempted because of that to say that I'm bad at it. But someone here just posted on a thread a still from slog and their grade. I tried with the compressed image on a free photo app, pixlr, to see what I could do with it and ejoyed my grade more than the one they posted with it, even though I only touched brightness, contrast,  saturation, and the tiniest hue adjustment, in absence of white balance or or color shift/tint type of options. What exactly is so hard about grading log images? Assuming people are saying you need a vast understanding of curves etc? Or is it possibly really that simple? I realize this is a little off topic and I should hit up tutorials and try out better grading software than I've used up to now.

Share this post


Link to post
Share on other sites

Shoot log with your wb set up correctly and you dont need to do any grading at all! - just use your curves/levels to get to the contrast level which leaves the highlights unclipped, themids natural and the shadows not crushed.  then boost saturation if required.  

Share this post


Link to post
Share on other sites

Sooo.. I have very little experience grading. Tempted because of that to say that I'm bad at it. But someone here just posted on a thread a still from slog and their grade. I tried with the compressed image on a free photo app, pixlr, to see what I could do with it and ejoyed my grade more than the one they posted with it, even though I only touched brightness, contrast,  saturation, and the tiniest hue adjustment, in absence of white balance or or color shift/tint type of options. What exactly is so hard about grading log images? Assuming people are saying you need a vast understanding of curves etc? Or is it possibly really that simple? I realize this is a little off topic and I should hit up tutorials and try out better grading software than I've used up to now.

It depends - grading can be as simple or as complex as you like. 

Share this post


Link to post
Share on other sites

Shoot log with your wb set up correctly and you dont need to do any grading at all! - just use your curves/levels to get to the contrast level which leaves the highlights unclipped, themids natural and the shadows not crushed.  then boost saturation if required.  

That's the problem, with log and a tiny screen without luts wrong wb doesn't stand out as much so it's very easy to get it wrong. Alien skin is the result, unless you spend a lot of time on them curves and get it somewhat right, but there is where 8bit tells you to fuck off.

Share this post


Link to post
Share on other sites

My personal opinion: most people are crap at grading.

This became evident when Magic Lantern RAW gave everyone the possibility to pull off extreme grades with the raw files... this resulted in a lot of terrible grades. Same happens with the LOG footage from the A7S and GH4.

I think this is a a bigger issue than 8 bit vs 10 bit.

Haha - yes exactly this. Most people don't realise that colour grading is something that really can take years to master. The colourists I work with have been working for years as colourist, and one of my go-to's spent a year and a half observing before being allowed anywhere near the wheels.

The whole 'democatisation' as they say, of the film industry, with better and better technology becoming cheaper and cheaper - has lead to a subsection of the market who expect to not have to learn or do anything, and yet still get the same/similar results to a Hollywood film.

I've seen some utterly horrible skin tones out of Canon cameras - and yet people here talk about how much 'better' the Canon colours are. There are terrible grades galore all over the internet.

Could be true too. 

In the following video (hope Andrew does not block it :p)  they used two cameras FS7 and A7s. Can you guess which images come from which camera? Hint: compare 1:43 to 1:44. 

https://vimeo.com/134440445

 

IMO, knowing how my A7s behaves with skin, it becomes pretty easy to pick which is which - however, that's not to say that the A7s is awful at rendering skin tones, and certainly I've gotten some great skin tones out of it. If you light it right, you can get incrdible images out of it. IMO, the general public wouldn't be able to tell the difference between the two cameras in general viewing.

I think it really is a matter of people being overall terrible at colour grading - and that's fine, it's a whole extra skill, and if you've shot and attempted to grade 10-bit codecs, then you can deceive yourself into thinking you understand colour and grading, when in actuality all you've done is add a curve here or there, and the fact that it is 10-bit ProRes or raw means that it's a lot more forgiving and easier to get at least a 'pleasing' look. 

It becomes obvious if you read through the 'history' of the A7s colour issues - first the A7s was too green, then it was too yellow, now it's too plasticky....

I often shoot PP off on my A7s for real quick turn-around stuff, and it's great. Even when shooting Slog2, I haven't really had any issues with colour - even skin tones. That being said, if you under-expose skin on the A7s, it can start to disintegrate relatively quickly. 

Share this post


Link to post
Share on other sites
Guest Ebrahim Saadawi

Just one opinion I want to add to this discussion: Theory and numbers aren't always 100% applicable to real imagery. 

I've de-logged and heavily graded some 8bit Log images without issues (C100) and de-logged and pushed 12bit log images with lots of issues (BM4K)

There's more than the codec to the final grade-ability of the image, starting from the lens, the image sensor performance (noise performance, cleanliness, fpn, DR, colour dye, resolution), the processor tricks, NR, colour science, WB, exposure, gain,   gamma curve, happening before compression and all directly affect how much the image can be pushed and de-logged with or without issues, not just 8bit vs 10bit. 

Share this post


Link to post
Share on other sites

The main problem with people shooting S-LOG specifically is that they're using S-Gamut in 8-bit, which if you know anything about color spaces is a HORRIBLE idea. You shot your 50mbps 8-bit codec in an enormous twisted-axis color space and tried to color correct it yourself? Without LUTs? Are you INSANE?

I suppose I'm ahead of the curve because I know I'm shit with color correction. Besides the cheap and dirty DrewNetwork workflow for quick jobs, I use Speedlooks on all my footage. It gives me a great range of base looks that I can tweak a little to my personal taste. 

Share this post


Link to post
Share on other sites

Just one opinion I want to add to this discussion: Theory and numbers aren't always 100% applicable to real imagery. 

I've de-logged and heavily graded some 8bit Log images without issues (C100) and de-logged and pushed 12bit log images with lots of issues (BM4K)

This is also very true. The specific log curves are designed for each camera, which is why the specific Slog2 on the A7s, for example, is actually a different Slog2 to the one you'll find one the F5. They're similar, but they're both designed for the different cameras. The A7s Slog2 is much closer to the F3's Slog2 (and to be 100% honest, I find the colours to be very similar between the two).

I've also found grading Blackmagic log footage to be much more annoying than any other camera, even thought it its 10-bit ProRes

The main problem with people shooting S-LOG specifically is that they're using S-Gamut in 8-bit, which if you know anything about color spaces is a HORRIBLE idea. You shot your 50mbps 8-bit codec in an enormous twisted-axis color space and tried to color correct it yourself? Without LUTs? Are you INSANE?

It's not insane. It's actually totally fine - you just need to know how to grade it. XAVC-S is a lot more malleable than H.264. The one thing that initially put me off the A7s was the 8-bit Slog thing (I said to the guy - do you really think it's a good idea to shoot Slog in an 8-bit codec?). It's pretty good though. It's no 10-bit XAVC from the F5, but it can still be pushed a fair bit. 

Personally, I prefer to shoot to a Shogun or similar in ProRes 422HQ, which gives you a much nicer base to start with (and also gives you a waveform so you're not guessing about exposure, or needing to pull out your meter for every shot).

Share this post


Link to post
Share on other sites

With LOG comes great power and it is down to the user how good ends up looking. There's a lot of terrible looking LOG footage out there due to the individual grade rather than any codec weakness and I don't think 10bit ProRes LOG from the Blackmagic Cameras looks significantly different or better to 8bit LOG. 10bit is overrated for everything aside from keying. I have graded 10bit from the GH4 to Shogun and didn't see an advantage in the grade even when pushing it to extremes to see what was lurking in the murky depths!! In my view, it doesn't suddenly benefit skin tones. That is more down to the sensor and image processor than 8bit vs 10bit.

Take for example 14bit raw as one extreme in terms of colour / bit depth... only way you can go more extreme on the specs than that is 16bit on the Sony F65! To make use of 10bit let alone 14bit and 16bit the sensor has to deliver an extremely wide dynamic range AS WELL AS a massive colour gamut. Now, we already have experience of 14bit with Magic Lantern raw. Is it significantly better than 10bit raw from a Blackmagic in terms of codec or grading flexibility? No. The sensor makes more difference. The sensor in the 5D Mark III is very good, very clean, wide colour gamut. The one in the BMPC is noisy and has a harsh run off into the highlights. Great codec, yes, but 10bit vs 14bit with that same sensor performance would have made very little difference.

Now we have a shining example of how good 8bit LOG can look for colour... he is called Mr Canon 1D C. You saw how it compared to the NX1 which I previously sung the praises of for being actually very very nice indeed at capturing vivid, rich, satisfying rec.709 colour.

What LOG does for a camera, regardless of 8bit vs 10bit, is quite frankly magic and should be highly regarded.

There's 'light LOG' like on the 1D C by the way, which doesn't go as flat as S-LOG and doesn't dramatically change colour, leaving it very saturated. I think S-LOG does go to extremes in terms of dynamic range... but it is not 8bit which causes the weirder colour vs the 1D C is it? Because they are both 8bit codecs! A7S owners, indeed RX10 II, RX100 IV owners can do an experiment. Shoot 4K 8bit LOG video. Shoot a raw still. Grade to match. Compare. Difference will be smaller than you think!

Share this post


Link to post
Share on other sites

There's more than the codec to the final grade-ability of the image, starting from the lens, the image sensor performance (noise performance, cleanliness, fpn, DR, colour dye, resolution), the processor tricks, NR, colour science, WB, exposure, gain,   gamma curve, happening before compression and all directly affect how much the image can be pushed and de-logged with or without issues, not just 8bit vs 10bit. 

Of course. I hope I didn't imply such a thing. My point was that an 8 bit codec can be very limiting when grading a LOG file. There are plenty of other things that limit the grading too.   

I have graded 10bit from the GH4 to Shogun and didn't see an advantage in the grade even when pushing it to extremes to see what was lurking in the murky depths!! In my view, it doesn't suddenly benefit skin tones.

When the V-Log gets released it will be interesting to redo that test. 

Share this post


Link to post
Share on other sites

Log is a compromise of normal 8 bit color for better dynamic range.  You can lose some detail because you are recording colors with less disparity and gradient information between two objects.  Plus, it takes a lot of knowledge, effort, and experience to grade 8 bit color because any small adjustment in post can and probably will clip a some color information in some parts of the image.  Then you have to start manipulating individual colors rather than doing a white balance adjustment, which will never look as good as white balanced raw image.

Avoid using log when possible by improving your lighting.  When you really need the dynamic range and you want to sacrifice some detail, you can use log.

Share this post


Link to post
Share on other sites

That's the problem, with log and a tiny screen without luts wrong wb doesn't stand out as much so it's very easy to get it wrong. Alien skin is the result, unless you spend a lot of time on them curves and get it somewhat right, but there is where 8bit tells you to fuck off.

There's no way to get anything wrong IMO.  if youre outdoors shoot with the correct wb for the setting.   or better - go AWB - awb is surprisingly trustworthy in natural light.  I trust it better than my own judgement in fact.  if youre in mixed lighting indoors - tungsten, led's and a bit of light coming through the windows from outdoors, choose the wb setting which best suits - somewhere in the middle of them all, or the setting for which ever light source is the most important to be 'correct'..  again, AWB is often the most effective system for these problem spaces.  

Dont touch your r, g or b curves at all.  just adjust the curves for the R+G+B until you have a smooth gradient from highlights to blacks and everything in between.  8 bit only seems to break up for me when I need to hit a single channel a lot more than another.  if Wb is set correctly very rare does it take much more than a tiny tweek to one channel for me to see stuff I like.

 

This said, I dont bother with log myself since my a7s needs an inch worth of ND's to bring the native 3200iso down to a manageable base!  however if i was in a situation where I wanted to keep cloud formations unclipped i'd nd up and go s-log, with the correct wb setting for the scene.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×