White Point Setting

The curves dialog box allows you to view value information in RGB (0-255) or ink percentage (0% to 100%) values.

 
 
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Value Readout in Ink Percentage

Light (0-255 RGB) vs. Ink Percentage Readout

I recommend viewing the curves dialog box value information readout in ink percentages simply to make the relationships easier to understand. It is easier to comprehend percentage changes on a scale from 0 to 100 than on a scale from 0 to 255. Ink percentage is a 0 to 100 scale.Light readout is a 0 to 255 scale.

 
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White Point, Black Point, Mid Tone, 1/4 Tone, and 3/4 Tone

Five Tones of the Tone System

When we use the Tone system for color correcting, we are concerned with five specific tones: White Point, Black Point, Mid Tone, 1/4 Tone, and 3/4 Tone. Adjustment of these five tones encompasses the first five steps of the color correction routine.

(Though I enjoy the nod to Ansel Adams' "Zone System" in the name "Tone System", these tonal points are actually the source of this workflow's name.)

On the next page we will look at setting the White Point's target values.

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