[A] [B] [C] [D] [E] [F] [G] [H] [I] [J] [K] [L] [M] [N] [P] [Q] [R] [S] [T] [U] [V] [W] [X] [Y] [Z]
OBJECTIVE - An objective (or object lens, object glass, objective lens or photographic objective) is an optical system or device containing a combination of lenses that receive light rays from an object and form an image on the focal plane. A photographic lens is an objective.
OCCLUDE - To block the passage of, as in "to occlude light."
OFF THE FILM METERING - Known also by its initials, OTF metering is an exposure meter reading that measures light reflected from the surface of the film during exposure.
OPACITY - (1) State or quality of being opaque. (2) The degree to which a substance is or may be opaque. (3) The proportion of the light that is absorbed by the emulsion on any given area of the negative.
OPAQUE - (1) Does not transmit light. (2) Coloring used in photography to render parts of a negative opaque.
OPAQUE BODIES - Objects that permit no light to pass through them, but reflect light.
OPEN UP - Increase aperture size or reduce shutter speed to permit more light to reach the film or image sensor.
OPTICAL GLASS - High-quality, color-free glass having specific refractive qualities, used in lenses and other components of optical systems.
OPTICAL ZOOM - A true zoom effect unlike a digital camera's digital zoom. Optical zoom changes the focal length of a lens.
OPTICS - The branch of physical science that deals with the properties and phenomena of both visible and invisible light and with vision.
ORTHOCHROMATIC or "Ortho" - (1) Representing correctly the relations of colors as found in a photographic subject. (2) A photographic emulsion sensitive to all visible colors except red - i.e. an ortho film is sensitive to blue and green light.
OTF - Off the film
OVER-EXPOSE - Expose a photographic emulsion or a digital image sensor to more than light than is necessary for proper exposure.
OVEREXPOSURE - Overexposure occurs when a photograph receives too much light. It results in a loss of resolution (very fine detail), more graininess and less detail in highlight areas. An overexposed negative is very dense resulting in light prints. An overexposed slide or over-exposure with a digital camera displays very light density. Intentional over-exposure or underexposure is known as increasing or decreasing exposure.