All lights, except those driven by pure DC, will have a periodic flicker rate (normally undetectable to the eye) which may have to be taken into account for image capture. With AC driven tungsten lamps the thermal inertia of the filaments may be sufficient to allow this effect to be largely (though not completely) ignored. Discharge lamps such as HMIs and
flourescents are more complicated. In some instances synchronisation of the shutter to the flicker rate has to be used; in the case of "flicker free" HMIs a square wave drive with an intentional frequency offset is employed; and, commonly for flourescents, a very high frequency switching rate can be used with multiple "flashes" for each frame. In each case these types of technique will only be valid for a limited range of shutter and frame rates

LED lights driven with PWM or PAM current are also a discontinuous source of light. They require exactly the same degree of caution for image capture purposes as every other AC driven lamp. If in doubt, test.

Gekko Technology Ltd products such as george™, kisslite®, lenslite® and kuelite™ are driven with PAM and PWM.