Severe contrast enhancements: on 45% rule — and cats

Started Jun 28, 2013 | Discussions thread
Charles2 Veteran Member • Posts: 5,132
Two great tools for these operations

Two great tools for these operations:

Picture Window Pro gives you the three HSV curves and the three HSL curves, as well as the three RGB curves. PWP just emerged from a thorough beta testing of version 7, so now is a good time to take it for a trial drive.

Raw Therapee gives you the three LAB curves as well as exquisite control over exposure (.01 stop) and also over a Black Point slider. Most of its operations work on TIFs and JPGs; the program demosaics virtually all Bayer camera raw files.

For practical work, the discussion of the HSV and HSL spaces by Norman Koren is helpful. He summarizes:

  • Darkening in HSV reduces saturation. Darkening in HSL increases saturation when L > 0.5.
  • Lightening in HSV increases saturation. Lightening in HSL reduces saturation when L > 0.5.

So, for example, if you want the lighter portion of the image to become "richer" and to pop, apply HSL-L contrast, favoring the darkening point, on an upper portion of the curve.

As for adjusting the R, G, and B curves, this method can be a subtle way to get the color balance you need. Also, digital emulations of films like Provia and Portra are available as sets of R,G,B manipulations, which you can apply in PWP then adjust for a specific image.

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