FS7: FS7 RAW woes & data distribution between: 12-bit RAW, 16-bit RAW, & 10-bit S-Log

Ben Scott said:
In all honesty I am really not a fan of Philip Bloom and his ethics statement is a joke. The man is a shill. I'll leave the other more serious accusations levelled at him to one side.
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LOL, that has made my day :)

Tom, no one is smearing anyone. We all have an opinion and being British we always say it how it is. I believe Ben's comment is correct, however I do find Bloom amusing and prefer to watch his videos than an episode of Coronation Street. You can't beat a bit of the old camera porn.

Ben Scott said:
That said he had issues with the Epic when it came out - and Jim Jannard's response was unbelievable in its aggressive and combative nature. Frankly that whole episode (and Bloom didn't come out of it smelling of roses either) caused a huge shift in the way the company was run and not too long after Jim Jannard moved permanently behind the scenes and left Jarred Land to be the more public face of the company. On the client-facing side, the Red of today is not the Red of 2010/2011. That goes for the company as well as the cameras in my opinion.
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How much do you think a fully working Raven will be with everything needed? I have noticed CVP are selling RED cameras now which is an interesting move for RED. I can't wait for some real world tests with this camera.

Ben Scott said:
As for Arri... They are winning on just about everything else. It's cool that they are behind on resolution and price.
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I have a feeling Arri will never sell low price cameras. Perhaps it would affect it's reputation as being a professional company. I think Arri are quite happy selling accessories for the F5 and other brands of lower end cameras. I wish Panavision would bring something to the table. Have you seen the rig they built for the F55, man that is one nice piece of kit.

Product_Sony F55_Back.jpg
 
cameramanben said:
Hi yoclay,

S-Log2 is defined by:
if x>=90 {
IRE = 219.0 * (power(10.0, (( (x–64)/(940-64) – 0.616596 – 0.03 ) / 0.432699 )) – 0.037584) / 155.0
} else {
IRE = ( (x-64)/(940-64) – 0.030001222851889303 ) / 3.53881278538813
}
where 'x' is the 10-bit code value (or whatever bit depth scaled to 0-1023)
source: Sony S-Log2 Technical Paper

S-Log3 is defined by:
If in >= 0.01125000 {
out = (420.0 + log10((in + 0.01) / (0.18 + 0.01)) * 261.5) / 1023.0
} else {
out = (in * (171.2102946929 – 95.0)/0.01125000 + 95.0) / 1023.0
}
Where:
in = reflection
reflection = IRE * 0.9
out 0.0 - 1.0
Source : Sony S-Log3 Technical Paper

Those are the precise transfer functions used - there are are no unknown bumps and shoulders. The primaries and white points are also defined in the sources, and since these are equated in strict linear space (confirmed if you look at the ACES IDTs) the definitions are exquisitely exact and comprehensive. In fact the only significant point not mentioned but which I fairly easily found out using the spreadsheet of matrices which Sony published with the S-Log3 documentation is that CIECAT02 seems to be the chromatic adaptation model used to shift white points.

The cameras will likely use lookup tables rather than do the calculations on the fly, but this is unquestionably what gets recorded. As might be a bit obvious, I have written an app to shift between colourspaces, perform log exposure shifts and other adjustments and in testing and in my work as a cameraman I check on this over and over again.

You are quite right that by reducing the contrast to fit more at the extremes, you also reduce the contrast in the midtones and hence the spread of possible data values in the midlle stop to stop (when compared to linear, or frankly more usefully Rec709 or sRGB). However...

Rec709 is generally viewed at an 8-bit colour depth, and whilst any sensible Rec709-based camera curve incorporates a knee, I'll use the base display curve as an example since it makes things as difficult as possible for log. The Rec709 display curve spreads the highest stop (going from mid gray, that is stop 1 1/3 to stop 2 1/3) roughly between 70% and 100% IRE. in 10-bit land 0%-100% is 876 code values (64-940), so 30% IRE would be about 263 code values. Divide by 1023 then multiply by 255 to get the 8-bit equivalent and rounding up that's about 66 8-bit code value. Again, no knee and the greatest spread. In a real 8-bit Rec709 camera curve no stop is likely to get near that, particularly stop zero to stop one which is the skin tone mids area which really sets how many code values you need to trick the eye.

Anyway, getting back to 66 code values, here is a chart I prepared for an article a while back which uses the defining equations to give an idea of code values per stop for various 10-bit log curves (plus 8-bit C-Log):
View attachment 107768
Zero on the x-axis is 18% gray, so what this plots is the shadow stops. With all of the included curves the values per stop increase above stop zero. If you look at the y-axis, you can see that both S-Log3 and Arri LogC pass 66 code values at stop -2, with S-Log2 only a little behind. What that mean is that in purely available information terms, you could expand the contrast of any stop from two stops below mid gray through to white clip (in the Sony cameras this is exactly six stops above mid gray for both S-Log2 and S-Log3) and have as much data available to you as broadcast display Rec709 in the top 30% IRE. Again, the stops above mid gray still have more data spread in the log curves, but this is showing the worst case scenario.

The two biggest issues I have come across in the end results from log are the codec choice and the appropriate use of the right tools for 'de-logging' to image for display

Very sorry to have been so long-winded, but it often comes up that people think that log curves are ambiguous or unknown, but at least in Sony's case the documentation is extensive, detailed and publically available. I really do think that it is important to be clear about that.

I've included pretty much every mathematically documented log curve I could find in my LUTCalc app, and posted links to the bulk of the sources on the webpage if you are interested,

Ben
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Hi Ben,
Well there appears to be at least one person here which knows the values of these curves, so that is a good thing. If indeed you are correct, I very clearly see a bump on the SLOG3 curve exactly in the area I was speaking about. What concerns me about it is what happens just to the right of it. You will notice all the other curves are fairly long in their transitions. That bump is either compensation for somthing particular to the sensor or an artificial boost for some particular set of values. As always there is a price to be paid and we may be looking at it in terms of the issues that are being experienced.
 
Hi yoclay,

the bumps in S-Log3 and Arri LogC in the chart I posted are just a consequence of the transition from the linear portion of the transfer function to the log section deep in the shadows. If you look at the x-axis, this is at around four stops below mid gray, ie in the case of Sony S-Log3 around ten stops down from white clip. It is noticable because that chart is code values per stop against stop, ie the slope of the log curve against stop. You would be hard pressed to spot them on a code values v stop chart.

All of these curves are totally monotonic, which means that as the stop rises, so does the code value. In fact, even these code value per stop v stop charts are actually monotonic too. Because of that and the fact that the equations are fully defined it is pretty easy to incorporate the linear to log transition in exposure or other adjustment calculations (which I do in LUTCalc).

the transition helps to avoid divisions by zero in the maths close to absolute black.

As a comparison, true Rec709 and sRGB are also both piecewise curves, with a linear portion in the shadows followed by a power law curve. That's why Rec709 is thought of as being net gamma 1.9 even though the actual exponent is 2.22 and sRGB 2.2 even though the exponent is 2.4,

Ben
 
JackCarter said:
How much do you think a fully working Raven will be with everything needed? I have noticed CVP are selling RED cameras now which is an interesting move for RED. I can't wait for some real world tests with this camera.
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Well the ready to shoot bundle is about £7,000 but that's nowhere near ready to shoot in my opinion. Buy the brain and 4.7" touch monitor separately. Buy the OFFHOLLYWOOD expander with XLRs and V Mount (price tbc) But a couple of 240GB cards to start you off. Buy a reader.

If you already have some v-mount batteries, I think £10,000 will get you a decent enough kit ready to go shoot for a day.

People do need to get their head around the cost of the camera not being £4,000. It's a modular camera with over a hundred permutations tabled for how it can be setup. The brain is just 1 part of those modules. It's a great idea to be honest.
 
Curved TV?

It's like I don't know you any more :(

As an aside, an interesting quote from the chief colour scientist at Spectracal, Stacey Spears

Any display you buy this year or next is disposable with the HDR format war that is happening.
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Haha the market material for that 120" monitor is hilarious, look at the DR image and the colourspace illustration.
 
And who can argue with 'awe-inspiring level of contrast'?

Hate to think what it does to Scandinavian Police dramas.
 
Ben Scott said:
Well the ready to shoot bundle is about £7,000 but that's nowhere near ready to shoot in my opinion. Buy the brain and 4.7" touch monitor separately. Buy the OFFHOLLYWOOD expander with XLRs and V Mount (price tbc) But a couple of 240GB cards to start you off. Buy a reader.

If you already have some v-mount batteries, I think £10,000 will get you a decent enough kit ready to go shoot for a day.

People do need to get their head around the cost of the camera not being £4,000. It's a modular camera with over a hundred permutations tabled for how it can be setup. The brain is just 1 part of those modules. It's a great idea to be honest.
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It will probably work out as the same price as the F5 with EVF etc. Hmmmm will see how it pans out.

I wonder will the Raven look as good as this? That is some serious camera porn.

https://www.youtube.com/watch?v=qsk2wsIODPo

 
starcentral said:
I'll see your RED Weapon Dragon - Camera Test 2015 and raise you a RED Dragon vs C500 Test!

https://www.youtube.com/watch?v=KdW8HCIX62o
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I prefer the younger bird in my post :) I don't think much to Canon.

I'll raise you with a real project shot on the F55.

https://www.youtube.com/watch?v=6wEJpVCTWs8


I think it looks damn good! It must have been shot on a pre-production model but with S-Log3 it would have looked even better. Do we really need RED Dennis?

https://vimeo.com/74518845


And I've never see this one before but some of those images are striking.
 
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starcentral said:
Dig does't impress me, and apparently was shot in RAW but I bet no one knew a decent workflow for it at the time.

In the meantime, Sense8 (4K netflix show) is shot on the F55 + RAW and from what I know coloured by Technicolor. They obviously know the secret to unlocking the beast:
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I like the film Dig but I agree some of the grading could be better. I think Earth Air Fire Water is a better film, but I prefer films without dialogue which let the images tell the story.

I don't know what it is about Sense8, it looks like cheap television to me. The motion is not very cinematic and all that fast editing looks cheap and tasteless kind of like Fast & Furious.

Not that the content interests me, but at least this F55 footage looks like a film.

https://vimeo.com/102171990

 
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