Calibration Spreadsheets

A spreadsheet with data for color calibration of imaging software.

There are two issues with trying to calibrate imaging software - in what units is the readout, and secondly what adjustments are being applied to the image. Typically, when a raw developer loads a TIFF file, it does so without adjustment, but usually applies some kind of tone curve when loading a raw file.

The readout units for some of the raw developers that I've calibrated are:

  1. Lightroom: Melissa RGB - Melissa RGB is the combination of the ProPhoto primaries and the sRBG gamma curve, Also known as "bastard RGB", as it's the bastard child of ProPhoto and sRGB.
  2. Aperture: Wide Gamut.
  3. Capture One: Capture One uses whatever color space is set as its output space, so you can set it to any ICM profile you have. For a bunch of ICM profiles you can use, see the ICM Profiles page.

The adjustments made by default are more complex - generally, each raw developer has its own tone curve. What I've done is to use the monochrome stepwedge reference image (available on the Reference images page) to work out what the tone curve is, then adjust the color profiles of the GretagMacbeth test chart by that tone curve. This gives color values for each raw developer that take into account both the color space and the default tone curve.

The spreadsheet is here: RawCalibration.xls 

It has sheets with the straight (non tone curve adjusted) RGB values of each patch in the Melissa RGB, WideGamut and ProPhoto spaces, as well as sheets with RGB values for Lightroom's default settings (V1.3.1), Aperture's default settings (V1.5.4) and Capture One (V4) for various output profiles. There is also a sheet with the values of the stepwedge test image.

The data is based on information from Bruce Lindbloom's site, and the GretagMacBeth test chart documentation.