WA8LMF Home Page | Photo & Travel Index Page | Updated 30 Oct 1999

Screen Calibration

Scroll Down for More Pictures The range of brightness and contrast in high-quality uncompressed photos far exceeds the range typically encountered in graphics screens produced by normal computer software. Your monitor must be adjusted properly to display photos properly. The tests below can assist in setting up your monitor. The background for the second item below is 50% gray (RGB 127,127,127) while the background for the third item is 17% grey (RGB 211,211,211)
Contrast and Brightness Test -- This is a scan of a test target supplied with CorelPaint 8.0. Remove any screen-darkening anti-glare filter covering your screen. Turn your monitor brightness control all the way up (if this text starts becoming fuzzy, back off just slightly until it is clear). Then adjust your monitor contrast control until the right most two bars of the gray scale are black and the 3rd bar from the right is just barely detectable. The leftmost two bars are both 100% White (RGB 255,255,255); the rightmost two are both 100% black (RGB 0,0,0)
Monitor Gamma Test -- Gamma is the non-proportional rate at which a monitor screen "gets brighter" as the electrical signal applied to it increases. Increasing gamma value makes the darkest parts of a picture get brighter faster than the lighter areas. This brings out shadow detail without burning out the highlights. Most PC-based image-editing applications assume your monitor has a gamma of 2.2 and make corrections to the image data as they send it to your screen. If gamma is being over-corrected for your monitor, the dark areas will be pale and washed out looking (too light). If gamma is being under-corrected, the dark areas will look excessively dark; trying to fix this by turning up the brightness will merely wash out the highlights.

This test pattern can reveal the actual monitor gamma. Once you have determined this, a (very) few monitors and some programs will allow you to make compensating adjustments. To use the test, blur your eyes or move far enough away from your monitor so that you can't see the textured pattern in the background of this image. The square whose brightness most closely matches the background shows the current gamma of your monitor.

Another Test Card in PNG (Portable Network Graphics) format -- This may not reproduce on older browsers.

The gray scale bars range from 0 (100% Black) to 255 (100% White). The black square has a letter "B" at RGB 11,11,11 in it; the white square has a letter "W" at RGB 240, 240 240 in it. Depending on the gamma characteristics of your monitor, you may not see one or both of the letters. This target tests the ability of your system to reveal detail in the extreme dark and light parts of an image.

The bright color squares are (left-to-right): 255R and 255G [100% Yellow in CMY system], 255G and 255B [100% Cyan in CMY System], 255G, 255R and 255G [100% Magenta in CMY system], 255R, and finally 255B.

The third row of vertical stripes of varying width alternate between 100% black and 100% white.




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