Photo Glossary

Radiography

Technique of using X-rays, gamma rays and charged particles to form shadow images on photographic materials. Used in medical and industrial research because of its ability to penetrate opaque objects.

RAM

Random Access Memory.Temporary computer memory, used to store data and software while in use.

Rangefinder

Device in some cameras used to measure the distance from the camera to the subject.

Rasterization

The process of converting a graphic image to a bitmap.

Rasterize

The process of converting a vector image into a bitmap image.

Raw

A picture file format that some of the more advanced cameras have the option of using when taking photographs.

Rear focus

The focused area behind the subject.

Rear focusing system

System where only the rear lens group moves during focusing. It eliminates changes in the physical length of the lens during focusing.

Rebate

The unexposed areas surrounding the images recorded on film.

Reconstructed image

An image that has been restored and repaired.

Recycling time

Time it takes a flash unit to recharge between firings.

Red eye

A photographic effect caused by light reflecting off the interior surface of the eye, which produces a red glare within the eye.

Reflected light

Light bounced off a subject, not falling on it.

Reflected light reading

Measurement by a light meter of the amount of reflected light being bounced of the subject.

Reflection

Rays of light which strike a surface and bounce back again.

Reflector

A device used to reflect light onto a subject.

Reflex camera

A camera that uses a mirror to reflect light onto a ground glass for viewing and focusing.

Refraction

When light rays change path as they pass through one transparent object, such as a lens element, to the next.

Relative aperture

This is the diameter of the aperture of a camera divided by the focal length of the lens. Expressed numerically as an f-stop.

Repeating flash

A feature available in some units to make multiple flash bursts during exposure. Useful for motion study in single frame multiple exposure.

Resample

In graphics software, the resample command is used to increase or decrease the size and/or resolution of a bitmap-based image.

Resolution

A measure of the proportion of the smallest individually accessible portion of a video image to the overall size of the image.

Reticulation

Cracking or distorting of the emulsion during processing, usually caused by wide temperature or chemical-activity differences between the solutions.

Retouching photo

To improve a photo image using the tools available in a photo manipulation program. Improvements can include everything from more refined colors to improved clarity.

Reversal materials

Materials specifically designed to be processed to a positive after one camera exposure.

RGB

Red, Green and Blue. They colors represent the additive color model, where 0% of each component yields black and 100% of each component yields white.

Ring flash

Ring shaped electronic flash unit attached to the front of a lens. Used to give even frontal lighting in macro photography.