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videovillage / community

Feature requests, bug tracking, questions, and issues for Filmbox, Scatter, Screen, and Lattice. Also general questions about color science and filmmaking are welcome!
https://github.com/orgs/videovillage/discussions
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L* Gamma support #12

Closed radioproektor closed 1 year ago

radioproektor commented 6 years ago

It seems your app missing L* Gamma support. Here are some links about it: http://stonerosephotos.com/blog/2010/09/gamma-the-zone-system/ http://forum.luminous-landscape.com/index.php?topic=38535 https://www.dpreview.com/forums/thread/3069106 http://www.colormanagement.org/en/workingspaces.html

radioproektor commented 5 years ago

Here is another source with a lot math formulas and explanation of this gamma http://www.marcelpatek.com/gamma.html search for L-star curve part in the middle of the article

radioproektor commented 4 years ago

So any hope to see this option somehow? L gamma curve is perfect for inverting film negatives. Here is real life usage example: for most accurate results film negative scanned in linear gamma and should be inverted before transformation to working color space. Invert tool don't works in linear gamma as it should, so we need to transform Linear to L gamma, next do invert, and next transform back from L gamma to Linear. If instead Lgamma we use sRGB or something like 2.2gamma, invert will produce less accurate results and will shift tonal values after invert.

radioproektor commented 4 years ago

some additional info and formulas here https://en.wikipedia.org/wiki/Lightness

radioproektor commented 4 years ago

By the way, i noticed that L* gamma seems may be different between apps. For Example ICC v4 profile generated with ICC Profile Editor in RawTherapee have some additional lines in formula. As result if i use v4 ICC profile in PhotoLine app, some correction tools don't work as expected. Seems some compatibility issues with ICC v4... Screen Shot 2020-11-05 at 9 51 41 PM