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# Set Gamma Dialog Help Window

LProf is an open source application that creates ICC profile for cameras, scanners and monitors.

#### Setting Gamma and Black Point

This is by far the most important setting when making a rough monitor profile. You can link the red, green and blue channels together and adjust them all to the same value or they can be unlinked and individually adjusted.

On the dialog are two charts. One is small and the other is large. These charts will assist you with setting both the gamma and the monitor black point. These charts are both used with permission from Norman Koren. Please see the Norman Koren Monitor Calibration Web Page for more details about these charts.

The small chart is a fixed gamma 2.2 only chart. The large chart will directly read out the gamma on a sliding scale. When the small chart is a consistent color all the way across the gamma sliders have been correctly adjusted. The large chart will show a band that has a consistent color that corresponds to the currently set gamma. In addition, the black level segment of the large chart will aid in setting monitor black point. These charts allow users to make very accurate and repeatable gamma adjustments.

For best results make these adjustments in a darkened room and maximize the gamma dialog. Start out with the color channels linked and adjust the slider until the small chart is all one shade of gray. Then adjust your monitors "brightness" control (this is really the black point control) until the just visable bars in the black level part of the large chart are visable across from the point marked 2.2 on the large chart. Depending on how much you adjusted the black level you will likely have to go back and adjust the gamma slider again to get the gamma to be 2.2 again. You may have to repeat this process several times to get both black point and gamma correct. At that point you can unlink the color channels and adjust the gamma of each color channel. On many monitors this may not be necessary. You should obtain a typical value of 2.4-2.6 on most CRT monitors. The profiler will give you a profile that corrects this to 2.2 which is the recommended gamma for monitors.

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