Conclusion

There is an important monitor property that these test pages don't deal with. It is the gamut, that is, the amount of color saturation the monitor can display. In order to display a really deep red, green, or blue color, the monitor should have a large gamut. Gamuts are often expressed as a percentage of the standard NTSC gamut; for standard LCD monitors with a fluorescent tube backlight, it is 72% of NTSC, which means that they can produce less saturated colors than a CRT television. Some expensive LCD monitors use different backlight technologies and can produce 100% of NTSC or even more.

If you use these test images in a shop that has several monitors hooked up to the same computer, this can deteriorate the image quality. I used to say here that that might be an excuse of the salesman, but I have seen the difference between a direct VGA connection and one through a 16-way VGA splitter, which in this case turned out to saturate the 'quick contrast test' in the rightmost five (!) bars. Additionally, monitors may not be running at their native resolution in such a setup.