In his video Color Grading vs. Color Correction, Cullen Kelly’s articulation of the difference between Log and gamma sounds uncannily similar to our experience grading HDR footage in Final Cut Pro vs. DaVinci Resolve.
“Images can be encoded in a Log or a gamma state. Gamma encoding was devised for preparing an image for viewing on a display while Log encoding was devised for storing maximum dynamic range using a scheme similar to the one that our vision system does. Color correction traditionally operates on images when they’re in a gamma state owing to its history in broadcast video wherein last-minute corrections would be made just before a piece of content goes to air: a little more contrast here, a little less saturation there, etc. And while this may sound like a straightforward approach, it carries a lot of compromises – namely the tools that we have to use when we’re operating on images in this state are counterintuitive and complicated and they rarely translate from one shot to another. For example, if I want a shot and I want to make a simple exposure adjustment, I have to feel my way to that with a combination of lift, gamma and gain, and once I’ve done that, the recipe is unlikely to translate to any other shot but the one that I’m on. Color grading, by contrast, has its origins in color timing and digital intermediate and it’s much more accustomed to operating on images in a Log state. When we’re manipulating images in this state we can use simpler tools that feel more intuitive; they feel more like we’re manipulating physical light and shadow. For example, if I want to make that same exposure adjustment on an image in a Log state, I can do it with one knob – Offset – and having done that, that adjustment is far more likely to translate across multiple shots than if I’d made it when I was in a gamma environment”.
When working with HDR video in Final Cut Pro using the shadow, midtone and highlight wheels, it’s necessary to crank the levels drastically up or down in order to retain contrast when adjusting exposure, whereas in Resolve Studio, a slight manipulation of the global wheel in the HDR Palette is all that is required, as simply as adjusting the aperture on our camera lens (to borrow a phrase from Cullen) – just one reason why Final Cut Pro is unsuited to HDR grading.