As per a quick question with Julie over the twitters, I wanted to get a clear understanding of how draft is reading / interpreting data as it’s going through it’s processes. The last place I was in didn’t have a colour or pipeline person and often what happened was when clients supplied luts, they didn’t really perform as advertised and there was a fall back of faking something in nuke or using the lut and putting additional cc’s to try and match the target look of a final movie. This is generally kind of unsatisfying to me so I wanted to get some clarity as to what’s going on under the hood in draft and get predictable results. So say for example, I have a dpx sequence that’s in either redlog or alexalog, I want to apply a lut to that footage and save it out as a quicktime.
In nuke I’d load the sequence and set the colour space drop down to whatever the correct one is for the footage and this should in theory linearize the data. I now use a vectorfield op to load in my lut to apply the film’s look and render the result out as an srgb quicktime - lets say photojpeg or some other high quality method. I normally get a pretty good match when I place my QT over the nuke viewer and compare results.
In draft, if I try to do the same thing so I can batch quicktimes I’d do the following:
Load the dpx sequence in - At this point where we’ve only done a read, nothing else, what does draft treat the footage as in terms of colour space? Is it assuming that it’s always being fed linear data or is it autodetecting log versus lin based on header data / file extension?
Strip the log curve aka convert to linear - as far as I know I had to remove the log curve and here I create a cineon /alexalog / redlog lut, invert it since we’re stripping the curve and not applying it and then apply it to each image. The images are now linear after this process.
Apply the lut - normally I think we were using the ocio operator for this. So we load our Lut and apply it - again does ocio typically assume that it’s being fed linear? Excuse my ignorance but are there ever cases where people would wrap up the linearizing of a plate and a grade / look into a single ocio operation and we’d skip the linearizing step above? I’ll assume that it normally acts on linear and our lut is only a standard CC and not a major swing in colour space.
Convert to srgb for quicktime - Since we’re off to screen space we need to do a linear to srgb op to convert into gamma space. I’ve read the links on the forum about the various issues with quicktime gamma and often I’ve had to do a slight gamma / colour correction to counteract whatever darkening or washing the QT will do, dependent on codec.
Save out to quicktime - hurray!
Mainly Steps 1 and 3 are what I wanted to confirm as to how draft is loading things!