RACK AND PINION FOCUSING

Definition: mechanical focusing system used on copying or monorail cameras. A pinion engages a rack on a slide. Focusing is achieved by turning a knob or wheel, which moves the lens or image panel.

RADIOGRAPHY

Definition: 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

Definition: Random Access Memory. The high speed portion of the computer's memory that is held on special chips.

RAM (RANDOM ACCESS MEMORY)

Definition: The high-speed portion of the computer's memory that is held on special chips for use in current applications or procedures.

RANGEFINDER

Definition: A device included on many cameras as an aid in focusing.

Definition: focusing system which measures the distance from camera to subject.

Definition: 1. A device on a camera that measures the distance from camera to subject and shows when the subject is in focus. 2. A camera equipped with a rangefinder focusing device. Abbreviated RF

Definition: A device included on many cameras as an aid in focusing. See also Viewfinder, Parralax Error

RAPID FIXER

Definition: fixing solution that uses ammonium thiocyanate or thiosulfate instead of hypo.

RAPID RECTILINEAR

Definition: lens system composed of two matching doublet lenses, symmetrically placed around the focal aperture. It was introduced by Dallmeyer and Sternheil and removed many of the aberrations present in more simple constructions.

RASTER

RASTER
Definition: The series of lines of information such as the parallel and horizontal scan lines that form a television or video display image.

RASTER IMAGE

Definition: An image that is defined as a collection of pixels arranged in a rectangular array See "Bitmap. "

Definition: This is a resolution - dependant image that is produced using pixels. The quality of a low - resolution image decreases as you zoom in to the image. Photoshop is raster software.

RASTER SCAN

Definition: A scanning pattern, generally from left to right while progressing from top to bottom of the imaging sensor or the display monitor. Generally comprised of two fields composed of odd and even lines.

RASTER STREAK

Definition: A dark streak in photographs of television-screen or computer-monitor images, caused by using too fast a shutter speed.

RASTERIZATION

Definition: Changing vector type image information to raster image information.

Definition: Converting mathematical and digital information into a series of dots by an imagesetter for the production of negative or positive film.

RAW

Definition: The RAW image format is the data as it comes directly off the CCD, with no incamera processing is performed.

RAW DATA

Definition: Data that is not formatted or processed.

RAW IMAGE FORMAT

Definition: The most common image format amongst digital cameras is JPEG, it's a format which produces relatively small files from large amounts of image data by discarding certain information, as JPEG uses a "lossy compression algorithm". The only other common alternative is TIFF, this produces an uncompressed 24-bit per pixel image often in the multiple megabytes, certainly for a 3 megapixel camera in excess of 8 MB per image, not really practical. Each pixel of a CCD can only see one colour, depending on the CFA (colour filter array) placed over the CCD this is either Red/Green/Blue or Cyan/Magenta/Green/Yellow. The cameras internal image processing engine then interpolates colours from the value of neighboring pixels to calculate a full 24-bit colour for each pixel. RAW is simply the raw data as it comes directly off the CCD, no in-camera processing is performed. Typically this data is 8, 10 or 12 bits per pixel. The advantage being that file sizes are considerably smaller (e. g. 2160 x 1440 x 12 bits = 37,324,800 bits = 4,665,600 bytes), the image has not been processed or white balanced which means you can correct the image, and it's a better representation of the "digital negative" captured. The disadvantage is you can't open these image files with a normal photo package without using an "acquire module" (a plug-in, typically TWAIN, which can open / process such images). Advantages of RAW format A true "digital negative", untouched by cameras processing algorithms No sharpening applied No gamma or level correction applied No white balance applied No colour correction applied Lossless yet considerably smaller than TIFF Records data over a wider bit range (typically 10 or 12 bits) than JPEG or 8-bit TIFF Disadvantages of RAW format Requires proprietary acquire module (typically TWAIN) or plug-in to open images Images can take 20-40 seconds to process on an average machine No universally accepted RAW standard format, each manufacturer (even each camera) differs.

RAYOGRAPHS

Definition: term coined by Man Ray and his friends for pictures made by placing directly on photographic paper (i. e. photograms).

RC PAPER

Definition: See resin-coated paper.

REAR CURTAIN SYNC

Definition: when the flash fires an instant before the second or rear curtain of the focal plane shutter begins to move. When slow shutter speeds are used, this feature can create a blur effect from the ambient light, i. e. , patterns following a moving subject with subject movement frozen at the end.

REAR FOCUS

Definition: refers to the focused area behind the picture's subject.

REAR FOCUSING SYSTEM

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