[Joel Gerlach]

For anyone interested, I figured out my own answer by removing the rgbToHsl expression and replacing it with the individual RGB vector appropriate for each exposure. So I went into the Exposure settings, changed it to “individual channels” and then used the following expression on each channel’s exposure properties:

driverLayer = thisComp.layer("My sampleImage layer");
multiplier = 9;

lightnessSample = driverLayer.effect("Color Control")("Color");
driverLightness = lightnessSample[0];
driverLightness * multiplier;

Where lightnessSample[0] is set for Red, 1 for Green, and 2 for Blue. In order to mimic the higher contrast of the screen, I brought the gamma of the diffuse pass down to .38 (for each channel) and .65 for the glossy pass (as glossy surfaces are more visible than matte due to reflectivity). The end result is perfect, and will save a lot of render time. And, at least in AE CC2015 the sampleImage script runs incredibly smooth.

Thanks Kevin for your help!

[Joel Gerlach]

Kevin, quick question. I was thinking I could use an exposure effect and set the channels to individual so I could use sampleImage to drive exposure on a R,G,B basis and instead of transforming the color I could drive individual exposure channels after the color neutral CG theater pass.

About that, though, with the section
driverLightness = rgbToHsl(lightnessSample)[2];

That’s creating a saturation result, right? If I understand rgbToHsl correctly. If I was going to modify this expression to drive individual color channels would this still be the best approach? Final question: if the end result is R,G,B exposure values, I wouldn’t want to run this expression under each exposure value, should I modify the original sampleImage to give out those RGB values and then reference them in the exposure channels? Not sure the best way to approach that.

Thanks for your help. I owe you a big one. 🙂

[Joel Gerlach]

Kevin you’re a genius. Let me give it a go and see how it works out!