Nuke – Standard sRGB/3D-LUT vs. ACES 1.0.1

In the last years we got used to work in Nuke in a gamma- but not color managed way with the help of standard 3D-LUTs (ARRI or CINEON for RED material) or primary grade look LUTs from Resolve. Nuke handled the gamma, the 3D-LUTs handled the gamut.

This works fine in Compositing until you have to work with material form different cameras in the same shot.

I am using an ARRIRAW ALEXA 65 file (A003C025_150830_R0D0.0078471.ari) from the ARRI ALEXA SAMPLE FOOTAGE website. The 6k-file was cropped and scaled down to HD.

(1) – Nuke-Default color management (sRGB Viewer) : ALEXA LogC over Rec.709 (3D-LUT) – the same image that you see on set but without a 3D-LUT being baked in the image data.

(2) – Nuke ACES 1.0.1: ALEXA ACEScg over RRT-Rec.709

The two images are looking quite similar. The tone mapping of the RRT is a little brighter and shows more contrast. Both images are handled internally in scene linear light values. The tone mapping and gamut is happening in the viewer and only baked in the image date once it is written out for viewing the images.
Still these are two very different ways of working and handling the image data. (1) is not color managed whereas (2) is color managed by ACES.

(3) – ALEXA Linear over sRGB – standard look in Nuke

(4) – ALEXA ACEScg over RRT-sRGB D60 very warm colors – usually D65 is used

(3) ALEXA footage seen through the standard sRGB viewer. The image data is correct, the viewer can only show a small window of all the image data.

(4) An ACES limitation until version 1.0.2. The sRGB ODT is D60, but all the sRGB monitors that we usually use are D65.
The image looks too „warm“. OCIO 1.0.3 has a RRT-sRGB in D65.

(5) – ALEXA Linear over sRGB – this is only 5% of light – see how much dynamic range is captured

(6) – ALEXA ACEScg over RRT-Rec.709 – this is only 5% of light –  see how much dynamic range is captured

(5) and (6) show that in both cases the underlying image data is preserved. A simple multiplication of 0.05 was used.

…to be continued…