Incident Light – Light that falls on a surface and is not reflected by it. An incident light meter would be used to measure this for proper exposure settings.
Interchangeable Lens – Some camera systems offer the ability to swap lenses at any time and offer a magnitude of lenses for any given situation. Most commonly found on single-lens reflex (SLR) cameras.
ISO – Stands for “International Organization for Standardization,” a universal system to measure film speed. You will see this used as ISO 100 for 100 speed film.