Mapping Light, Shaping Color

Author: JRD

  • The Channel Mixer 100% Concept

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    JRD
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    There is persistent and pervasive advice that you should make your channel mixer output slider values sum to 100% in order to preserve overall image brightness, exposure, luminosity, etc. The concept certainly has its merits, but being dogmatic about it can lock us out of some very interesting Channel Mixer effects for different kinds of…

  • 16-Bit Color Range Selections with Channel Math

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    One of the most powerful features of Adobe Photoshop is the ability to restrict adjustments to specific regions of an image using masks. The simplest masks are based on gradients—linear, radial, or reflected—which allow broad spatial control over where an adjustment is applied. More advanced masks, however, can be defined directly from image data. These…

  • Color enhancement with the Photoshop Channel Mixer

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    RGB Curves, Color Balance, Selective Color, and HSL adjustments are powerful for color processing in Photoshop.  A much less-used option is the Channel Mixer in color mode. This is extremely unfortunate as, to my mind, it is the single most powerful adjustment layer for color correction, enhancement, and photorealistic color grading. The channel mixer is…

  • Mathematically Balanced 16-Bit Luminosity Masks

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    Pixel-based layer masks in Photoshop can control both where (spatially) and when (conditionally) an adjustment is applied.  The most common type of “when” mask is a so-called luminosity mask, using the luminosity information inherent in our image to target application of adjustment effects.  For example, if you want to apply a particular adjustment (saturation, brightness,…

  • Saturation, Chroma, and Luminosity

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    In my goal to develop a deeper understanding of color manipulation in Adobe Photoshop—particularly for photographic images—I’ve been working to model Photoshop adjustments and blend modes at a mathematician’s level. Along the way I discovered Desmos, a free and powerful graphing calculator designed for education. Many of the articles I write will make extensive use…

  • Welcome to Mapping Light, Shaping Color

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    I’ve been pursuing landscape and other forms of photography for some time, enjoying both the process of shooting in the field and the technical side of post-processing. Of all aspects of processing, I’ve found color to be the most challenging, and over time I’ve worked to refine a more systematic approach. Given my technical background,…