Pixel Magic Systems VPS3800 manual Basic Calibration

4.7.3 BASIC CALIBRATION

See Section 4.6.3 for help with picture calibration. Most of the basic steps for pixel-based displays apply except for CRT projectors. They may have more control over color balance, which generally involves the ability to calibrate and store color balance per projector source memory. Setting contrast or peak white level is more difficult with a CRT projector as the blue tube will normally be close to beam current-limiting at full IRE100 output over the whole screen. This can result in a color balance shift to red at very high output levels and also prevent the standard test disc methods of setting contrast from working 100% correctly. Some contrast level setting procedures used on test DVDs rely on the projector’s power supply voltage sagging under the load imposed. However, the majority of CRT projectors originate as over-specifed commercial units, where the power supply is unlikely to lower its output under high load conditions. Start with the projector’s contrast setting the same as you have previously used*, then make adjustments to obtain correct peak white levels on a variety of source material. Correct might be defined as realistic looking or comfortable to view.

*Some projectors have a very high manufacturer’s default contrast setting (ss high as 80%). Depending on projector model, tube condition and screen gain a contrast setting of 50-60% is more likely to produce realistic levels. As a side benefit, useable tube life will be significantly extended.

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