Got it thanks.
BTW: are you on Linux, Win, or what?
Sorry, i should have caught that one…
Windows 10
Sigh. I doubt that you will be any wiser from this answer, but…
a) You do have several negative values in the .cube
b) So darktable correctly issues warnings
c) but that does not explain why your exports sometimes do not match the edited RAW (here I take for granted that you have used the same .cube in them all???).
Suggestion in order to pinpoint problem: please test using a .cube that does not contain any neg values.
Have fun!
Claes in Lund, Sweden
Yes, same .cube for all. But with slightly different adjustments to the LAB luminosity curve.
The LUT are generated by the software to provide a particular solution. Im not sure how i can address the negative values. Also, the LUTs appear to work in terms of providing the correct transformation.
Aw, it is dead easy to remove the negative values from the .cube (which is a simple text file) – but I wonder why they were created in the first place, and wether they really should be 0.000… values, or what?
Ping @phweyland?
/Claes
I have no solution I’m afraid.
About the lut3d module itself.
A cube transformation transforms any triplet of values belonging to [0,1] to something else.
The image input values are clamped to [0,1], this is first source of distortion.
Since the last lut3d change, accepting cube values outside [0,1], the image output values can also be outside [0,1] (which wasn’t the case before the change). The destiny of those relies on the capacity of subsequent modules (and color spaces) to accept or not out of range values… There is no guarantee here I’m afraid.
I don’t know how 3D lut creator works, but the generated LUT depends on the image input bounds. There is may be a way to normalize them before calculating the lut … Or at least to match some input conditions / constraints … For what I know there is no out of range values in the distributed luts.
About the export, there is another issue (as you say that the images look good on the screen). Do you have any meaningful message ? Can you try to launch dt from the console the option -d all, capture the log into a file and share it ?
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