Solving dynamic range problems in a linear way

Ok, please fetch the last version and follow this tutorial:

  1. open an image and ensure, in the exposure module, that you have no clipped highlights or shadows. Don’t hesitate to push down the black level and the exposure level Capture%20du%202018-09-21%2018-00-01

  2. in the unbreak color profile, click on the “middle grey target value” color picker, then draw a rectangle over an area that is supposed to be 50 grey (or just choose the whole image to get its average luminance as a 50 grey reference
    Capture%20du%202018-09-21%2018-01-25 )

  3. click again on the color picker to fetch the actual luminance value (it won’t be saved until you click again on it)
    Capture%20du%202018-09-21%2018-04-08

  4. reproduce the same process on a black or near-black area, with the black relative exposure color picker (careful : it takes the average lightness of the area, not the minimum, to reduce the sensitivity to noise in low-lights, so you have to be accurate in your selection). It’s hard to have real black, so you can tweak the value a bit after the picking (which gives you a first idea to speed-up the process)
    Capture%20du%202018-09-21%2018-06-49

  5. to automatically adapt the dynamic range, use the last slider (contrast correction) and, again, the color picker. This time, it has to be on the whole image (dark and light areas) because it takes the extrema of it. Click again on the color picker to have te computations done or begin adjusting the contrast correction . A negative will give you a better contrast but will sacrifice the extremes of the dynamic range, a positive % will protect the extreme values better, but will look very dull.
    Capture%20du%202018-09-21%2018-15-33

  6. Now, the optimizer is automatic but not magical. It is sensitive to noise in low-lights, so you may have to tweak a bit more the black relative exposure so your histogram in log mode is well centered.

  7. This is now a sane base to color-grade, and tune the contrast in a linear way. However, you have to re-add contrast and fix he lightness before saving the picture in JPEG with a S tone-curve.
    Capture%20du%202018-09-21%2018-20-15

Note that I haven’t used anything else here than 3 modules (exposure, unbreak input profile and tone-curve), and yet I have clipped whites only in the sun (in red), and almost no clipped blacks (in blue) even though I have a nice contrast.

The photo is © rawfiner.

Benefits :

  • no over-saturation problems in highlights, thus no gamut clipping
  • no staircase effect in sharp contrasted transitions (branches/sky, bokeh rings, etc)
  • fully parametric log function, relatively easy to remap the histogram where you want it
  • clean linear base to perform any adjustements in a safe way without clipping (especially : local contrast, high-pass filter, etc.)
  • no need for the shadow-highlights module that can have a very damaging effect in many cases (local contrast reduction, loss of shape and transitions, borders effects, desaturation)
  • no need for fixed reverse-engineered manufacturer-like basecurves
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