Grip and Lighting Illustrated Online Dictionary for Film and Video Production

I - from Incandescent to Iris

I

Incandescent (literally "glowing") - is used to describe standard "household" tungsten light bulb. A tungsten filament in a vacuum creates a light with a 2800K (give or take) color temperature (towards the red end of the light spectrum).

Incident - light falling on a subject (not the light reflected from the subject) as measured with an incident light meter for lighting evaluation and camera exposure settings.

Insider - a piece of diffusion or gel placed inside a frame, close to the lens of a light, behind the barndoors (as opposed to an "outsider" rig, clipping gel or diffusion to the barndoor flaps).

Inkie/Inky  (aka brand names, Mini-Mole, Pepper, etc.) -  a 250-watt or less small fresnel light. The name may come from the phrase "inky-dinky" meaning "small".

Iris - 1. a variable and controllable opening on leko, Source 4 and other ellipsoidal lighting instruments used to shape the beam of light. 
2. the variable aperture behind the camera lens that controls exposure to the camera imaging device or film.
3. A circular wipe type effect used from silent films to present productions (occasionally).