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gialandra, the double-plot there is confusing because when the Base Tone Curve option is checked, the Base Tone Curve of the Base Profile (shown in red) is plotted in a linear space. Your modified tone curve (drawn in black) is plotted in a gamma 2.2 space. When the final profile gets created by the DNG PE, the base tone curve and your modified tone curve get composed together to create the final tone curve. So, for example, if the black tone curve contains no points except for the 2 endpoints (i.e., it is a straight line), then no modification of the base tone curve takes place, and the final tone curve is simply equal to the base tone curve.
Within ACR or LR, if you want to get exactly the tone rendering of the profile, you need to use the CR/LR default tone controls, which are Brightness 50, Contrast 25, and Point Curve set to Medium Contrast.
Thank you Chan.
What I'm looking for is to put in the DNG profile a tone curve that I have created in PS on a linear image. Is it possible?
In detail: I have converted the raw image in a tiff file in linear gamma. In PS I have attach its ICC profile, convert to Prophoto and I have created a RGB tone curve (ie, 1 point curve with value in 95 out 160)
Then, as reported above, in DNG PE I load that dng file, I choose the base camera profile, I go in the Tone Curve panel in the Base Tone Curve I set Linear, I click on the curve and I set in 95 out 160 and then I save the new profile.
What can you say?
Thank you again
This is mostly (*) possible, but not directly via the DNG PE. The issue is the encoding space. Your RGB tone curve that you describe above is defined in a gamma 1.8 space (since ProPhoto has a gamma encoding of 1.8 ). The (black) tone curve interface in DNG PE is defined in a gamma 2.2 space.
In other words, if x is a linear signal and x' is the transformed linear signal, then the math for the former case is effectively
x' = x ^ 1/1.8
x' = ApplyToneCurve (x')
x' = x ^ 1.8
whereas the math for the latter case is the same except for the use of 2.2 instead of 1.8.
You will need to perform the appropriate transformation so that your 1.8-relative tone curve is expressed properly in a 2.2 space.
Once you have the actual numeric curve worked out, one way to make the required tone curve is to edit the .dcpr (recipe) file from the DNG PE using a text editor.
(*) The reason I say "mostly" is because another detail is that the PS RGB tone curve is a 1D curve applied separately to each channel. This is not the way the tone curve works in Camera Raw.