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RANGEFINDER - An instrument for measuring the distance from the observer to a particular object, as for adjusting the focus of a camera. A rangefinder is included as an integral part of many cameras as a focusing aid.
RAW - Sometimes called camera raw, raw format, raw image format and raw. A digital image storage format that contains the most information possible from a camera's sensor. RAW data ( a RAW image file) is unprocessed. Some folks consider it to be the digital equivalent of a negative or a slide.
RAY - A line of light.
RC - Resin-coated.
READY LIGHT - A small light on a flash unit that indicates whether there is adequate power to fire the flash.
RECIPROCITY FAILURE - When a film’s speed cannot be relied upon for proper exposure at slow shutter speed, reciprocity failure (or the “Reciprocity effect”) is said to occur. Additional exposure is required in order to achieve proper exposure for that film, even though your light meter may say differently. The additional problem of a shift in color balance that occurs with reciprocity failure can be more troublesome.
RECIPROCITY FAILURE results in underexposure and a shift in color balance.
RECIPROCITY LAW - Aperture and shutter speed have a reciprocal relationship in making an exposure. Various different combinations of the two will produce the same exposure. The reciprocity law therefore means that an exposure provided by ƒ8 and 1/250 sec will gave the same results as ƒ11 and 1/125 sec., or ƒ16 and 1/60 sec., and so on. If one choice of settings provides proper exposure, then the others will as well. The reciprocity law states that Exposure = Intensity X Time. “Intensity” is the amount of light, and “Time” refers to how long that amount of light is allowed to act on the sensor or the film’s emulsion. The law “fails,” however, when slow shutter speeds change the film’s apparent speed characteristics, making it seem to have a slower speed and resulting in color shift.
RECYCLING TIME - Amount of time for a flash to recharge once fired.
RED EYE is actually an image of the retina at the inside back of the eyeball.
RED EYE - An image in which a subject’s iris or irises are red instead of black. The red eye effect is caused by light from a flash traveling through the iris and illuminating the retina at the interior back of the eye–– which is red in color due to its blood vessels –– and the camera capturing that redness on film or on a digital camera's sensor.
RED EYE REDUCTION - A feature of some cameras or flash units that is meant to reduce the effect of red eye by emitting a short initial flash or multiple bursts of light immediately before the picture is taken. The intended result is a forced reduction in the size of the subject's iris.
REFLECTED LIGHT RAYS - Those which are thrown off from an object.
REFLECTED LIGHT READING - An exposure meter reading of light reflected by a subject. The exposure meters in most cameras are reflected light meters.
REFLECTOR - Material used to reflect light onto a subject. A flash reflector is a shiny surface situated behind the flash tube that reflects light in a specific direction.
REFLEX CAMERA - A camera that has a mirror directly in the path of light traveling through the lens that reflects the scene to a viewing screen.
REFRACTION - Refraction is a change of direction of a ray of light. Light that is traveling in a straight line alters course - bends - when it strikes light-transmitting substances such as glass or clear plastic at any angle other than perpendicular.
It is good practice to have a model sign a Release upon the conclusion of a photo session.
RELEASE - Refers to a Model Release - a contract in which a model consents to the use of his or her images by the photographer or a third party.
REMBRANDT LIGHTING - In the photography studio, Rembrandt lighting combines a variation of butterfly lighting with short lighting.
RESIN COATED PAPER - Paper that has a water repellent base and is used for making photographic prints.
RESAMPLING - Occurs when an image editing program is used to change an image's size. Increasing an image's size requires the addition of new pixels and decreasing size removes pixels.
RESOLUTION - (1) Fine detail in an image. (2) Also means “Resolving power.” It refers to the number of pixels that fit into a given area, commonly measured in digital photography as pixels per inch (ppi).
RESOLVING POWER - Ability of film or a digital camera's sensor, the lens or both together to reproduce fine detail.
RETICULATION - Occurs during processing when the emulsion becomes cracked or distorted. The cause is usually exaggerated temperature variance or differences in chemical activity between solutions.
RETOUCH - To manually alter the appearance of a digital image file or a negative, slide or print using non-photographic methods, such as air-brushing, with the intention of improving the image’s appearance.
RGB - An acronym for the primary colors of light, Red, Green and Blue, used to produce all other colors.
RIM LIGHTING - Occurs when the main light is placed behind the subject so that the subject's face is completely in shadow, but there is a rim of light around the subject's head, like the corona in a full eclipse.
RING FLASH - A circular-shaped electronic flash unit that fits around a lens and provides shadowless, uniform frontal lighting, especially useful in closeup photography.
ROLL FILM - Film with a lightproof paper backing that is wound onto a spool, such as 120 film for medium format cameras.
A good rule for subject placement that generally results in a pleasing composition.
RULE OF THIRDS - The rule of thirds is a design principle based on a photographer/artist visualizing both the vertical and horizontal division of a composition into thirds, and then placing the subject where the lines intersect.