3D LUTs for A7S Slog2 and SGamut

[jcs]

SGamut is Sony's 'top-of-the-line' ultra-wide color space. Without a proper color transformation, SGamut is time consuming to color correct. After a bit of testing, including using a simple 3x3 linear color matrix (thank's dhessel), I found the best results with 3D LUTs. These will work in Resolve, Speedgrade, and PPro (load with a Lumetri Effect):

3D LUTs from Sony: http://community.sony.com/t5/F65/NEW-F65-3D-LUT-s/td-p/135903. Since the A7S gamma in Slog2 isn't full range, using the included Slog2+SGamut to Slog2+Rec709 3D LUT is a good starting point. Once converted to Rec709 color with the Slog2 curve, a custom curve can be used in Resolve, then the final look saved as a 3D LUT which can then be loaded into Premiere Pro (real-time effect). Here's Art Adam's article comparing Slog2+SGamut2 to Slog3+SGamut3: http://www.dvinfo.net/article/acquisition/sonyxdcam/sony_sgamut_vs_sgamut3.html .

Alister Chapman's A7S 3D LUTs: http://www.xdcam-user.com/2014/08/set-of-20-cube-luts-for-the-sony-a7s/ac-slog2-to-709-luts-v2/ . These are pretty nice too, and have versions for various levels of exposure. These might be helpful as Slog2+SGamut changes color behavior with exposure (fixed in Slog3+SGamut3). In my tests so far, the F65 LUT from Sony for Slog2+SGamut to Slog2+Rec709 appears to be working OK for skin tones.

Using Resolve 11 with the above LUTs it's possible to get some pretty impressive looking color and skin tones with SLog2 and SGamut. Also a good opportunity to learn more about Resolve (more impressive the more I learn about it). I'm currently comparing custom Rec709 picture profiles to SLog2+SGamut to see if it's possible to get the same looks using Rec709 in-camera (much easier to expose, focus, etc.). In other words, are there any practical advantages to using SGamut vs. Rec709-based color modes for the A7S?

 

[toxotis70]

if you want to match different clips  , from different cameras too , is easier to do with Sgamut.

The sgamut color space is twisted and when you are trying to match other cameras , is very useful to have wider color spaces (colors doesn't clip ) than rec 709.

 

If you have only one camera , the benefits are not so obvious... and you can try 709 Matrix

Sgamut is also usefull when you want to output in another media (print , cinema, etc) 

 

Heavy color correction is very demanding too, so its better to have wider color space to do so.

 

In Davinci , you have to use a LUT  in the END of nodes , or as an output LUT.

NEVER before, because you loose the 32 bit floating capabilities.

[Luke Mason]

Sony clearly stated in the A7s manual that S-Gamut on A7s is merely an "emulation" of true S-Gamut, so LUTs from F65/F55/F5/FS7 etc. won't work correctly.

[jcs]

Sony clearly stated in the A7s manual that S-Gamut on A7s is merely an "emulation" of true S-Gamut, so LUTs from F65/F55/F5/FS7 etc. won't work correctly.

​Did Sony release math/equations necessary to create a LUT/matrix which transforms A7S specific SGamut into Rec709 for the A7S?

[toxotis70]

Not yet, but film convert did...http://filmconvert.com

 

Here are the compatible cameras .... http://filmconvert.com/Help/Default.aspx?help_id=29

They made specific LUTs for A7s, i use them in FCPX  and Resolve

[toxotis70]

There is also Catalyst Browse form sony, you can try it,  it works well and have some unique features (transcoding to Prores , WB correction, etc).

You can also make your own LUT with this program and export as .cube file.

It will work with any program, such resolve, speed grade, Premiere,  FCPX and LUT utility etc

http://www.sonycreativesoftware.com/catalystbrowse

 

 

[Devon]

@JCS

"Since the A7S gamma in Slog2 isn't full range, using the included Slog2+SGamut to Slog2+Rec709 3D LUT is a good starting point." 

What do you mean by "Slog2 isn't full range?" 

[jcs]

15 hours ago, Devon said:

@JCS

"Since the A7S gamma in Slog2 isn't full range, using the included Slog2+SGamut to Slog2+Rec709 3D LUT is a good starting point." 

What do you mean by "Slog2 isn't full range?" 

Full range is 0-255, Slog2 is 16-235 (8-bit output range).

[Devon]

Thank you for clearing that up