Precision White Point and Black Point Targets
White Point Setting Determination
White Point/Base Value Evaluation
When you print the targets, make sure you print from a color managed workflow, profiled media/printer combination, and proper print settings. Let your target print dry for 30 minutes before evaluating it. Make sure you are in proper lighting and viewing conditions when you evaluate the target.
When you view the Precision White Point Target, you should look for two characteristics. One is the first "readily visible" difference between the Specific Test Value (240 in the example below) and the Base Value (255). Readily visible means just that, an obvious difference in value between the two values. To determine this, look at the checkerboard pattern above the center Specific Test Value square where it mixes with the Base Value.
White Point/Base Value Evaluation
The image to the left illustrates White Point/Base Value Evaluation for a specific test
value of 240 RGB. Determine the first "readily visible" difference between the Specific Test Value (240 in this example) and the Base Value (255). Readily visible means just that, an obvious difference in value between the two values. To determine this, look at the checkerboard pattern above the center Specific Test Value square where it mixes with the Base Value.
White Point/Relative Value Evaluation
The second characteristic is the amount of separation between the outer Relative Values (+3 and -3) and the Specific Test Value (again, 240 in the example below). The more separation there is in these values from the the Specific Test Value, the more quickly the highlight tones will show separation and detail when printed. To determine this, look at the checkerboard pattern in the lower right and left hand corners of the sample patch. This is where the Specific Test Value square mixes with the outer Relative Values. You are looking for the first separation in these values. If you notice a dramatic amount of separation in the Specific Test Value and the inner (+1 and -1) Relative Values, it may indicate a problem with your profile.
White Point/Relative Value Evaluation
The image to the left illustrates White Point/Relative Value Evaluation for a specific test
value of 240 RGB. Determine the first "readily visible" difference between the Specific Test Value (240 in this example) and the outer Relative Value (+3 and -3). To determine this, look at the checkerboard pattern in the lower right and left hand corners of the sample patch. You are looking for the first separation in these values.
Selecting the White Point Setting from the Base and Relative Value Determinations
Once you have made your visual comparison of these two characteristics, pick a suitable white point setting that works well for both of them. Usually they end up at about the same Specific Test Sample. When in doubt, use a lower (number) white point setting. You can experiment on actual images to get a feel for how different settings affect actual output.
To learn about applying these white and black point settings go to the
Tone System Color Correction Routine
section.
White Point and Black Point Targets Next Page • Page 1 • Page 2 • Page 3 • Page 5
