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Base Curves vs. Correctio Curves

marcisim
2013-08-26
2013-09-26
  • marcisim
    marcisim
    2013-08-26

    I am getting a little bit confused about the curves in UFRAW. In particular, I do not understand what does in practice "directly to every color channel" mean, compared to "applied to the luminosity channel in Lch(ab) space". (I just made two citations from the guide of UFRAW.)

    What I usually do is to upload fotogenetic curves in both of the stages, choose the one that I prefer photo per photo and finish the post production in gimp.

    Anyway, by now I upload curves from "fotogenetic_s_curves" package at the base curve stage in ufraw, and those from "fotogenetic_curve_archive" and from "fotogenetic_correction_curves_v4" in the correction of luminosity and saturation stage.

    I would like to now if it does make any sense or if I am using the two curves in the wrong way. Perhaps I did not understand their meaning and function.

     
    Last edit: marcisim 2013-08-26
  • Chun Li
    Chun Li
    2013-09-26

    I agree that the manual page is not very clear, and it took me a while to understand the distinction. The curve under the "Base curve" tab is applied to ALL channels (RGB) before gamma correction is applied. The fotogenetic curves should be used here. The curve under the "Correct luminosity, saturation" tab is applied only to the L channel in the LAB space and is applied after all the changes of the previous tabs. Because they modify the image information differently, for some photos treaking the base curve achieves a better result, and for some other photos, tweaking the luminosity curve is better.