AccuColor – XYZ Values

AccuColor needs the XYZ values of the 24 patches of the color checker chart you use. The inspect and record modes check and install those values. For an overview of all modes, see AccuColor.

inspect

The “inspect” mode has no inputs. It outputs a three-band floating-point image of 1 pixel by 24 scanlines: the three bands are the X, Y and Z values, and the 24 scanlines are the 24 patches of the chart. The patches are listed left to right, then top to bottom, so the last six are the gray patches of the bottom row. A separate window shows the standard illuminant (D50 or D65) the values were calculated for.

You can view the values as numbers with Print (an Advanced-level module), as here, or as an image with Show.

AccuColor in inspect mode, followed by Print

record

The “record” mode has one input: an image in the same format as the output of “inspect”, with the XYZ values of your chart. AccuColor saves them in your settings file, state.txt (see Installation and User Data), for future calibrations. It asks which standard illuminant (D50 or D65) the values were calculated for; the default is D50.

AccuColor in record mode, reading an XYZ image

Entering the values for a different chart

  1. Run AccuColor in “inspect” mode into Print, and copy the output into a new text file.
  2. Change the XYZ values to those of your chart, without changing the parentheses or the first line.
  3. Save the file with a .txt extension.
  4. Read the file with ReadImage into AccuColor in “record” mode.

Special thanks to Ken Boydston and Brian Amrine of MegaVision.