Fresnel’s and PC’s
A light which uses a circular reflector and which is named after the lens which it uses. The Fresnel lens is not very precise however and gives a very soft edged beam as well as spreading a great deal of light outside the beam (spill). The light can be focused in order to alter the size of the light beam but it cannot project Gobo images. Despite being not particularly efficient, the Fresnel is a good light for stage lighting, especially at close & medium ranges to the subject. Fresnel’s are also good at creating stage colour washes as they blend evenly from one source to another allowing a seamless wash to be created. Fresnel can also have barn-doors which allow you to shutter off the spill from the light.
PC (Pebble Convex)(Plano-Convex)
A cross between a Fresnel and a Profile which uses a rough reflector to diffuse the light, producing a beam which is similar to an out of focus Profile. The PC is more efficient than a Fresnel as it also produces less spill. They can come in exactly the same housing as a Fresnel, so can also use barn doors to be shaped. The main way to tell the two apart is by the lens shape / pattern. PC lenses normally consist of loads of pebbles or small bumps across the surface, as show in the picture.