For example, let’s say I have a TIF from a film scan that is already converted to a positive. I want to make adjustments to tone in a similar manner as I would to a RAW file using tone equalizer. Is it OK to use tone equalizer, or should I use a different module? Same question regarding color. Is it OK to use color equalizer, or should I use something like color zones or another module?
Is there a general rule that can answer these questions to for other modules? For example, use display referred instead of scene referred for TIF/JPEG editing?
Even before that, and not for Tiff maybe but for JPG which are likely in srgb or adobergb colorspace DT will use a working space of linear rec2020. I have always wondered if there is any implication from taking a small colorspace and expanding it, then editing and then bringing it back down to the small colorspace for exporting. I guess I should look at the code to see if it actually goes throught that for a jpg even though that is the specified working space but maybe it makes little difference. I conceptually understand the methods used to map down to a smaller colorspace but doing the reverse and then back seems like it might have the potential to introduce changes… or maybe its just really not an issue…
Thinking on it more the smaller gamut is part of the wider space so I guess if you just do absolute rendering for the conversion its not going to be an issue …
My non-expert and non-technical answer is I would use what ever looks good. But in the module managements ‘hamburger’ there is a module setup for displayed-referred which is what would be recommended to JPG and Tiff images. This might provide some guidance about modules recommended by the developers. Tone equalizer and color zones are included in the modules but color equalizer, filmic and sigmoid are not.
I use the same modules as raw. Typically, when I’m editing JPEG, it’s from a phone or older camera. Color Calibration and Tone Equalizer I’ve used quite frequently. Occasionally, Color Balance RGB. Beware the modules can cause clipping (e.g. why I use tone equalizer instead of exposure).
Because of quantisation, wide colour spaces should not be used with low bit depth.
Much of ProPhoto represents imaginary colours (outside the visible spectrum).
I think it’s perfectly fine to edit sRGB input in scene-referred Rec2020. With colours that become too bright or too saturated for display-referred sRGB output, the same output transformations have to be applied as for normal raw editing.
