Excessive light to detectors can be very harmful. Too much light, either monochromatic or wide band, can easily destroy photomultiplier tubes (PMTs). Charge-coupled devices (CCDs) cameras, of modern design, are typically made with cut-outs so that saturation beyond several pixels will cause them to shut off. Unfortunately, the detectors in the back of your eyes do not have automatic shut-off mechanisms, and can be easily destroyed with excessive light.

As a review of filters and cubes, keep in mind that the primary job for the excitation filter is to block all light other than the desired band being used to excite the fluorochrome. The primary job of the emission filter is to block the excitation source. If these two optics are chosen correctly and inserted in the beam path, the only light reaching the detector is the fluorescence emission from the fluorochrome. Nothing from the source should make it to the detector. This very weak emission intensity has no chance of harming the detectors. If these two optics are not perfectly matched, the excitation light may reach the detector and cause all sorts of problems.