Great idea. Fitting dynamic range into range of image without tonal distortion side-effects was another issue I was having. Any links to tutorials? I got my cameras and I got a x-rite color checker passport.
Also, it would be great for better mixing Rawtherapee raw processed with Prores, as I can just use log profile conversions to get to ArriLog in Resolve.
Interesting… how did you define the tone curve for lumariver/dcamprof?
I downloaded the JPEG, it definitely re-energizes the S-curve. You got me thinking to do something similar with ACES2065-1, although that is still scene-referred…
We consider the physical world of image capture to work linearly so ideally we would like our processing to also work linearly. That would be possible if certain conditions were met in practice that however typically are not. For instance CFA spectral sensitivity functions would ideally be linearly related to cone fundamentals in the retina. If they were all we would need is a 3x3 matrix to bop around the needed colorimetric spaces.
Unfortunately that’s not the case: sensor SSFs are just an approximation to the ideal, the problem is overdetermined, there is an infinite number of possibly ‘correct’ matrices, if we want just one the best we can do is come up with a Compromise Color Matrix that minimizes potential errors according to some criteria. Think of it as fitting a curve (or a plane or a solid) to a lot of noisy dots. We sometimes try to compensate for some of the biggest errors via a look up table, but even that is just another form of curve fitting that only really works for the finite number of tones that were corrected manually.
So no, the standard 3x3 matrix cannot be made to work perfectly every time, it can only be made to work ok most of the time. All solutions that look more pleasing are just that, more pleasing. This one time, or perhaps in these types of conditions.
Thanks for the link, I’ve translated the arri log tone curve EI800 to the g’mic parser and used it in photoflow before the conversion to the working space rec.2020 linear, I’ve then used only levels and curves for tone manipulation, no saturation or channel mixer module.
(x > cut) ? c * log10(a * x + b) + d: e * x + f
-fill i=i/255;if(i>0.010591,i=0.247190*(log(5.555556*i+0.052272)/log(10))+0.385537,i=5.367655*i+0.092809);i*255
@age Hey thanks for sharing that I never really got how to use the unbreak profile…clearly you do…I guess I need to get up to speed…just need some time to read…
I’m also interested in acheiving this, been trying with lutcalc and dcamprof but my image it’s sometimes overexposed (after converting it back to rec709 with a lut or with color space transform in resolve), should i try to match middle gray from both curves at 18% compensating with negative exposure (-2.4ev on linear to EI800 LogC) ? can you share your dcp?