Photographic Glossary-R

R3000
Chemical process for making prints from slides.

RA4
Process that producing slides from negatives.

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

Range Finder
Some cameras allow the user to look directly through the lens of the camera to see the image being photographed. Other cameras have a window with a small lens through which the users views the scene. These cameras are known as Range Finder cameras. They differ from SLR's because they do not display an image based on what the photographing lens is viewing.

Rangefinder
A device included on many cameras as an aid in focusing. Instrument for measuring distances from a given point, usually based on slightly separated views of the scene provided by mirrors or prisms. May be built into non-reflex cameras. Single-lens reflexes may have prismatic rangefinders built into their focusing screens. The Leica and the Contax G2 still keep the flag up in this areas.

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

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

Raw data
Data that is not formatted or processed.

RAW Image Format
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.

Rear-Curtain Sync
Flash fires an instant before the second (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., a flowing- light patterns following a moving subject with subject movement frozen at the end of the light flow. (See "Front-Curtain Sync".) Most mid range and top flight auto camera models have this feature.

Reboot
The process of turning a computer system or printer off and then back on again, to reload the software.

Reciprocity law
States that exposure = intensity x times, where intensity is equal to the amount of light and time is equal to the time that amount of light is allowed to act upon the photographic emulsion.

Reciprocity
Most films are designed to be exposed within a certain range of exposure times-usually between 1/15 second to 1/1000 second. When exposure times fall outside of this range-becoming either significantly longer or shorter-a film's characteristics may change. Loss of effective film speed, contrast changes, and (with color films) color shifts are the three common results. These changes are called reciprocity effect. Generally, as a quick reference, exposure beyond one second needs to compensate for this characteristic of film.

Reciprocity Failure
As film is exposed to light, it becomes less and less sensitive. The longer it is exposed, the less sensitive it become. On longer exposures, where the meter says 10 seconds, depending on the film it may take up to 1 min to expose the film properly due to reciprocity failure of the film. Films are designed to be exposed within a limited but practical brightness range. Reciprocity failure occurs when a film is exposed under conditions that are not within its design range. It usually becomes evident with very low shutter speeds, such as those used in dim night scenes. As a result of reciprocity failure, colour balance will shift and colours will seem less natural looking.

Recycling time
Is the time it takes a flash unit to recharge between firings.

Red eye
The appearance of deep red dots in the eyes of human and animal photographic subjects. Redeye is caused by the flash reflecting off the retina in their eyes. It can be prevented by adjusting the camera angle, being sure the subject does not look straight at the flash, or with a redeye-reducing pre-flash. The pre-flash causes the subjects' pupils to contract, reducing the visible retina and thus the possibility of light reflecting from it. When the pupils of the eyes are dilated, the light entering the eyes can reflect off the back of the eye, causing the redness seen in many pictures. This problem is almost always caused on cameras where the flash and lens are very close together, such as point and shoot cameras. There are a few methods of alleviating this problem. Many cameras now incorporate Red Eye Reduction methods which involve multiple strobes of the flash before the photo is taken. The multiple strobes cause the pupils to close, minimizing the ability of the light to reflect back to the camera from the rear of the eye. Another technique requires a Flash Bracket which moves the flash to a greater distance from the lens plane, changing the angle of incidence. Because the light is not coming from a source near the lens, light is not reflected back to the lens from the back of the eyes.

Red-eye Reduction Mode
A special flash mode whereby a pre-flash or a series of low-powered flashes are emitted before the main flash goes off to expose the picture. This causes the pupil in the human eye to close and helps eliminate red-eye.

Reducers
Are solution which removes silver from negatives and prints. They are used to diminish density and alter contrast on a photographic emulsion.

Reducing agent
Is a chemical in a developing solution which converts exposed silver halides to black metallic silver.

Reflected light reading
Is a measurement by a light meter of the amount of reflected light being bounced off the subject. The light meter is pointed towards the subject.

Reflections
Are rays of light which strikes a surface and bounce back again. Specular reflection occurs on even, polished surfaces; diffuse reflection occurs on uneven surfaces, when light scatters.

Reflector
Any device used to reflect light onto a subject to improve balance of exposure (contrast). Another way is to use fill in flash. Any material or surface that reflects light. Reflectors are often used in photography to soften the effect of the main light or to bounce illumination into subjects shadows. Light does not always fall exactly where you want it. For this reason reflectors are used. Reflectors are placed facing the light, reflecting the light to an area of the scene that is a little dark and needs illumination. Gold reflectors can be use to warm a scene because of the color changed caused by the gold reflector. Silver and white reflectors provide nearly the same color hue as daylight, with White more subtly filling shadows and the silver providing more "punch" and contrast. Other colored objects can be used to reflect colors differently. A slightly different approach is the use of a black reflector. Rather than reflecting light to a specific spot, it absorbs nearly all light causing that side of the scene to be darker than usual.

Reflex
A reflex camera is one that utilizes a mirror system to reflect the light, and therefore the image, coming through the lens, to a visible screen. The image seen in the cameras viewfinder then is the same image entering the lens. This system provides the most accurate framing and focusing. Most reflex cameras reveal a high percentage of the image that will be photographed, upwards of 80%. Some reflex cameras are able to show 100% of the image frame into the viewfinder. The reflex system avoids the parallax problem that plagues most direct view cameras.

Refractive index
A technical term used to describe the effect of a lens in causing light rays to bend; important aspect in lens design. Is a numerical value indicating the light bending power of a medium such as glass. The greater the bending power, the greater the refractive index.

Refresh rate
The rate at which an image is redrawn on a CRT. This is needed because the phosphors at each pixel are stimulated by the electron gun for only a brief time. The faster the refresh rate, the more stable an image will appear on the screen.

Registration marks
Small crosshair on film used to align individual layers of film negatives.

Relative aperture
Numerical expression of effective aperture, also known as f-number. Obtained by dividing focal length by diameter of effective aperture.

Release-Priority
For autofocus, shutter can be released anytime (i.e., even when subject is not in focus). Helps you avoid missed opportunities when you are not concerned with absolute focusing precision, terms apply primarily for Nikon.

Replenisher
A substance added to some types of developers after use to replace exhausted chemicals so that the developer can be used again.

Reproduction ratio
Term used in macrophotography to indicate the magnification of a subject; specifically the size of the image recorded on film divided by the actual size of the subject; for example, if the image on film is the same size as the subject, the reproduction ratio is written as 1:1 or 1X

Resample
To change the resolution of an image.
Resolution: Refers to the sharpness and clarity of an image. The term is most often used to describe monitors, printers, and bit-mapped graphic images. In the case of dot-matrix and laser printers, the resolution indicates the number of dots per inch. For example, a 300-dpi (dots per inch) printer is one that is capable of printing 300 distinct dots in a line 1 inch long. This means it can print 90,000 dots per square inch. For graphics monitors, the screen resolution signifies the number of dots (pixels) on the entire screen. For example, a 640-by-480 pixel screen is capable of displaying 640 distinct dots on each of 480 lines, or about 300,000 pixels. This translates into different dpi measurements depending on the size of the screen. For example, a 15-inch VGA monitor (640x480) displays about 50 dots per inch. Printers, monitors, scanners, and other I/O devices are often classified as high resolution, medium resolution, or low resolution. The actual resolution ranges for each of these grades is constantly shifting as the technology improves.

Resolution
Refers to the sharpness and clarity of an image. The term is most often used to describe monitors, printers, and bit-mapped graphic images. In the case of dot-matrix and laser printers, the resolution indicates the number of dots per inch. For example, a 300-dpi (dots per inch) printer is one that is capable of printing 300 distinct dots in a line 1 inch long. This means it can print 90,000 dots per square inch. For graphics monitors, the screen resolution signifies the number of dots (pixels) on the entire screen. For example, a 640-by-480 pixel screen is capable of displaying 640 distinct dots on each of 480 lines, or about 300,000 pixels. This translates into different dpi measurements depending on the size of the screen. For example, a 15-inch VGA monitor (640x480) displays about 50 dots per inch. Printers, monitors, scanners, and other I/O devices are often classified as high resolution, medium resolution, or low resolution. The actual resolution ranges for each of these grades is constantly shifting as the technology improves.
Standard resolution is 640 x 480 pixels (H x V) and originates with the VGA standard first defined for the IBM PC. SVGA is the next step up in terms of resolution and covers 800 x 600. XGA define the 1024 x 768 resolution, while UXGA is used for 1280x1024 and 1600x1200. The higher the resolution the finer the image detail that can be seen. The ability of a lens to discern small detail; in photography, the image resolution in the final photograph depends on the resolving power of the sensitive emulsion and on that of the lens, the two are not related, but the effective resolution is a function of both; for reasonably accurate photographic measurements of lens resolution, the sensitive material must therefore have a much greater resolving power than the lens.

Resolution, output
The number of dots per inch, dpi, used to display an image on a display device (monitor) or in print.

Resolving power
The resolving power of a lens is a measure of its ability to closely spaced objects so they are recognizable as individual objects. It is determined by photographing a series of closely spaced lines, measuring the spacing between the most closely spaced lines that appear separate on film. The resolving power is expressed as the number of lines pairs per millimeter.

Reticulation
A crinkling of the gelatin emulsion on film that can be caused by extreme changes of temperature or acidity / alkalinity during processing. Cracking or distorting of the emulsion during processing, usually caused by wide temperature or chemical-activity differences between the solutions.

Retina
The area at the back of the human eye that converts incoming light into electrical impulses sent to the brain.

Retouching
Altering a print or negative after development by use of dyes or pencils to alter tones of highlights, shadows, and other details, or to remove blemishes. Removing imperfection or unwanted portions of an image.

Retrofocus Design
In a retrofocus design, which is advantageously applied to wideangle lenses, the back focus is designed longer than the lens' focal length to allow clearance for the movement of the reflex-mirror (No Mirror Lock up or separate viewing accessory attachment is required). It consists of front diverging and rear converging lens groups, as opposed to the telephoto design, and is therefore also called the inverted telephoto design.

Reversal film
Film that produces a positive image (transparency) on exposure and development.

Reversal Rings
These rings allow you to use the filter mounts on the front of a lens to attach a lens backwards to a camera body. The method allows for extreme macro photography with out purchasing expensive equipment. The disadvantage is that there is a very limited DOF and loss of between 3 and 4 stops.

Reversal
A process for making a positive image directly from film exposed in the camera; also for making a negative image directly from a negative or a positive image from a positive transparency.

RGB
The red, green & blue, the black is simulated colour. CMYK is the four primary colours. The red, green, and blue colour model used for scanners and monitors.
 

RIFF (Raster Image File Format)
A storage format used with gray-scale images.

Right reading
The correct orientation of a negative or transparency when the image appears as it did to the camera. Both negative and transparencies should be viewed with the emulsion side down and the base facing the observer. The emulsion side is dull-finished and very slight ridges can often be seen at the edges of the image elements. The base side appears glossy and smooth.

Rimlighting
Lighting in which the subject appears outlined against a dark background. Usually the light source is above and behind the subject, but rimlit photographs can look quite different from conventional backlit images, in which the background is usually bright.

Ring flash
A circular-shaped electronic flash unit that fits around a lens and provides shadowless, uniform frontal lighting, especially useful in close-up photography.

Ring light
A circular lamp or bundles of optical fibers arranged around the perimeter of an objective lens to illuminate the object in the field below it. A wide variety of sizes are available on both a stock and custom basis.

Rinse
Is a brief clean water wash between steps of a processing cycle to reduce carry-over of one solution into another.

ROM
Read Only Memory. A memory type that cannot be change or rewritten and will not lose information when a computer is turned off.

Royalty
Payment to the holder of a patent or copyright or resource for the right to use their property

Rubber stamp
This tool is used to retouch flaws, make a copy of a selected area and paste it elsewhere, or reproduce an object.

Rule of thirds
A general composition guideline that divides the negative frame into thirds horizontally and vertically to position the subject