White Point and Black Point Targets
Precision White Point and Black Point Targets
Once you have calibrated and profiled your monitor and profiled your printer, you need to systemize your printing by outputting white point and black point visual evaluation targets. By printing out the Precision White and Black Point Targets through a color managed workflow with the proper print settings, you will have the proper visual information to determine the appropriate white and black point settings for your image.
Even with a calibrated and profiled system, you still need to make a visual evaluation of the white and black point settings. These settings are made in conjunction with the six-step Tone System Color Correction Routine. A combination of factors require this visual evaluation. Theoretically, the profiling process should handle highlight (white point) and shadow (black point) separation. However, spectrophotometers can differentiate value more precisely than the human vision system and ink-jet printers are limited in how little or how much ink they can precisely deliver. Because of these factors, we need to visually place the white and black points. Black point compensation is thought to adjust the black point for varying media and color spaces, but testing has shown that it does not do enough.
White Point Target 255 to 238 Black Point Target 10 to 26
This target is designed to cover most printers typical black and white points. The left side has 18 white point target values from 255 down to 238. The right side contains 17 black point target values from 10 to 26 plus an additional target value of 3 for confirmation or proper printing.
This target should be sufficient to determine proper black and white point for most printer/ media combinations.
Black Point Target 0 to 35
This target is designed to ensure defining the black point in printers with lower black point capabilities. The range of 0R 0G 0B to 35R 35G 35B will cover almost any printers black point abilities.
WP/BP Test Image Target
The White Point/Black Point Test Image Target is designed to confirm the theoretical white and black points determine with the other targets.
The average human being can differentiate approximately 180 to 200 shades of gray. If I gave you 1000 gray paint chip samples that each differed slightly in value, and I asked you to sort them into like values (and I didn't tell you they were all different), you would sort them into about 180-200 piles. This explains why the magic number for digital images is 256 -8 bits. 8 bit images (2 to the 8th power) have 256 value possibilities. A lower bit depth (2 to the 8th power=128 values) will not offer enough values to satisfy the human vision system that the image is continuous in tone.