To allow applications to support only subsets of the MPEG-2 standard, it defines profile and level. An application may use the subsets of main profile and main level - often written as MP@ML - offering limited capabilities.canonglossaryus
Same as Key light - the principal, dominant source of light, usually in a studio, and generally the brightest light on a subject or scene.
Rotating electronic wheel device on camera s top plate, with click-stops in both directions, to change or select, depending on control or mode selected.
see Key Light
: is the main light source for a photograph. It could be the sun, a studio strobe, a flash, a reflector or something else. But it is the source of light that is producing the pattern of light on the subject with the most intensity.