The Gamut of CRT Monitors

With ICC color-managed workflow knowing the actual gamut of the monitor becomes a very critical piece of data that is required for accurate calibration.

Monitor manufacturers usually do not list the gamut in the specifications, however this information is stored into the monitor, called EDID information, and can be inspected using a suitable software.

To query the phosphors x,y chromaticities from the monitor please download the free DDCtest utility, kindly provided by EnTech Taiwan, (scroll down to the Free Software -section there) it is 137kB only and needs no installation, just download it to a suitable directly and then run (double-click it) from there.

The phosphors information are entered to the AdobeGamma, from the Phosphors dropdown select Custom. In this section the user tells to AdobeGamma what the hardware gamut actually is, AdobeGamma does not modify the system gamut based on these values, it simply stores these values into the system ICC profile so that Photoshop (as well as all the other ICC color-managed software) knows the actual hardware gamut and therefore can have/show accurate working-space inside Photoshop.

The phosphors x,y chromaticity values in the EDID are usually correct, phosphor manufacturers specify them accurately per scientific measurements. The gamma value in EDID is usually something like 2.5 or 2.2, it is simply written there by the CRT manufacturers, if it would be an accurate measurement then it would have more decimals (like the x and y chromaticity values have) than just one decimal. The whitepoint x,y is measured by the the CRT manufacturers and it is not clear what it means because the monitor has the adjustable color temperature controls, I believe that the whitepoint x,y chromaticity is that "white" when the custom color temperature controls of the monitor are all set to maximum.

The DDCtest utility only works with Win95/98, but the full PowerStip program (shareware) (scroll down to the bottom of the page there) does work on Win2000 etc. and has an evaluation period so it will be functional. In case you use the full Powerstrip program be sure that the Read data directly from monitor is selected.

Powerstrip Monitor information dialog

Gamut Comparisons

For gamut comparisons of monitors I've created a small Excel workbook that allows visual comparison between the the monitors gamut and the familiar named gamuts like Trinitron, ColormatchRGB, sRGB etc.

The workbook contains EDID information from 44 different monitors.