Replacing one projector in a multi-projector system is not simply a hardware swap. The replacement unit must be integrated into the existing optical, geometric and calibration relationships of the complete canvas. Differences in model, lens, firmware, operating hours, brightness, white balance, gamma and color can make the new projector visible even when the physical image position appears correct. This guide explains how to evaluate compatibility and recalibrate a replacement projector in immersive, mapping, museum, dome and other multi-projector installations.