Systems and methods for preventing high-radiant-flux light, such as laser light or a nuclear flash, from causing harm to imaging devices, such as a camera or telescope. The optical components of the imaging device have first and second foci. The second focus forms an image on an array of photodetectors and occurs at a large f-number. The first focus occurs at a small f-number in a gas that is dense enough to dissipate most of a femtosecond laser pulse of potentially damaging intensity and conditioned to easily undergo dielectric breakdown when exposed to high-radiant-flux light that is less intense than a femtosecond laser pulse. Dielectric breakdown forms a conductive arc that dissipates or scatters light, blocking high-radiant-flux light from reaching the array of photodetectors. Several methods may be used for conditioning the gas to break down quickly when exposed to laser attack.