Photography glossary - D
D-76 Developer for black and white films manufactured by Kodak.
DAM -Software - Digital Asset Management software
Daguerreotype - first practical and commercial photographic
process, introduced by Louis Daguerre in 1839. The sensitive
material comprised silver iodide, deposited on a polished silver
plated copper base. A positive image was produced by camera
exposure and mercury "development", which turned light struck
halides gray-white. The image was made permanent by immersing
the plate in a solution of sodium chloride.
Darkcloth - cloth made of dark material placed over the
photographers head and the camera back to facilitate the viewing
of images on the ground glass screen of sheet film cameras.
Darkfield - method of illumination used in photomicography that
will show a specimen against a dark or black background.
Darkroom - light tight room used for processing and printing. It
usually incorporates safe lighting suitable for the materials in use.
Darkslide - slide-in plastic sheet used on sheet film cameras over
the front of the film holder to protect the emulsion from light.
Dark Noise The charge accumulated by pixels while not exposed to light. Normally, this charge is reduced or eliminated prior to capturing a picture.
Data transmission - The exchange of digital information between two or more computers. Data is usually transmitted via a direct cable connection, a computer network or telephone lines.
Data security - A collective term used for any measure to protect and store files as well as programs for an extended period of time.
Daylight enlarger - early type of enlarger using light from a hole
in a window to provide illumination of the negative.
Daylight color film - color film intended for use with daylight or a
light source of similar temperature. The film is color balanced to
5400 K.
Daylight tank - light tight container for film processing.
Day rate - Minimum fee that Photographers charge for a day''''''''''''''''s work weather a full day is spent on a shoot or not
DCF - Design Rule for Camera File System – an industry standard for saving digital images. This not only determines the file type, but also sets the rule for naming the folder and file structure. It allows the conversion of uncompressed files into compressed JPEG files.
Decompression The process of restoring the contents of a compressed file.
Dedicated flash - flash gun designed to integrate automatically
into a cameras exposure reading and shutter circuitry.
Definition - subjective term for the clarity of a negative or print.
Delayed action - operation of the shutter some time after the
release is depressed. Most shutters have a delayed action timer
built in.
Dense - describes a negative or an area of a negative in which a
large amount of silver has been deposited.
Densitometer - instrument for measuring the density of silver
deposits on a developed image by transmitted or reflected light.
Density - amount of silver deposit produced by exposure and
development. It is measured in terms of the logarithm of opacity,
where opacity is the light stopping power of a medium.
Depth of field - distance between the nearest point and the
farthest point in the subject which is perceived as acceptable sharp
along a common image plane.
Depth of field scale - The distance between the nearest and farthest points that appear in acceptably sharp focus in a photograph. Depth of field varies with lens aperture, focal length, and camera-to-subject distance.
Depth of focus - distance which the film plane can be moved
while maintaining an acceptably sharp image without refocusing
the lens.
Desensitizing - reducing an exposed emulsion''''''''''''''''s sensitivity to
light. This can be done by the application of dyes or by using
oxidation agents.
Detective camera - popular Victorian camera which was designed
to appear as a bowler hat, pocket watch or binoculars.
Developer - chemical bath containing reducing agents, which
converts exposed silver halides to black metallic silver, making the
latent image visible.
Development - process of converting exposed silver halides to a
visible image.
Diaphragm - term used to describe the adjustable aperture of a
lens. It controls the amount of light passing into the camera and
may be in front of, within or behind the lens.
Diaphragm shutter - between the lens camera shutter that
performs the function of the iris diaphragm.
Diapositive- positive image produced on a transparent support
for viewing by transmitted light, i.e. transparency.
Diazo - abbreviation of diazonium compounds, which decompose
under the action of intense blue or ultraviolet radiation, forming an
image in an azo dye.
Dichroic - displaying two colors - one by transmitted and one by
reflected light.
Dichroic filters - produced by metallic surface coatings on glass
to form colors by interference of light. Used in high quality color
enlarger heads.
Dichroic fog - purple-green bloom usually seen on negatives and
caused by the formation of silver in the presence of an acid.
Differential focusing - setting the camera controls to produce
minimum depth of field, so that image sharpness is limited to a
particular subject element.
Diffraction - light rays scattered and change direction when they
are passed through a small hole or close to an opaque surface.
Diffraction grating - optical attachment that separates light into
its constituent colors.
Diffuse lighting - lighting that is low or moderate in contrast, such
as on an overcast day.
Diffuser - any material that can scatter or diffuse light. The effect
is to soften the character of light. The closer a diffuser is to a light
source the less it scatters light.
Diffusing - process of softening detail in a print with a diffusion
disk or other material that scatters light.
Diffusion condenser enlarger - enlarger that combines diffuse
light with a condenser system, producing more contrast and
sharper detail than a diffusion enlarger but less contrast than a
condenser enlarger.
Diffusion enlarger - enlarger that scatters light before it strikes
the negative, distributing light evenly on the negative. Detail is not
as sharp as with a condenser enlarger.
Digital - Opposite of analog. Digital information is made up of a limited number of gradations (e.g. 256 colours, 8 →bit). The change from one digital element to the next is always "step by step" and not continuous.
Digitalization - AD-conversion.
Digital camera - Filmless camera that usually captures images with the help of a CCD chip or cmos chip. The image data received is then saved to special memory cards or other storage media.
Digital flash - Computer controlled flash.
Digital Negative (DNG) The public, archival format for digital camera raw data developed by Adobe DNG is an open standard file format for raw camera data and can include the original file as well as metadata information
Digital Imaging Software - Image editing software.
Digital tele - Thanks to special algorithms, some digital cameras are able to provide a zoom effect by re-calculating the captured image data. See Digital Zoom
Digital Zoom A digital magnification of the center 50% of an image. Digital zooms increase the apparent image size by interpolation. They do not increase the amount of image information.
Digitization The process of converting analog information into digital format.
Dilution - reduction in the strength of a liquid by mixing it with an
appropriate quantity of water.
Dimensional stability - substance''''''''''''''''s ability to remain unchanging
in size when subjected to processing and drying.
DIN - Deutsche Industrie Norm (German Standards Organization).
DIN speed - system used by the German Standards Organization.
Diopter - unit used to express the power of a lens. It is the
reciprocal of the focal length expressed in meters.
Dioptric adjustment - See diopter correction
Diopter Correction An adjustment on the viewfinder of a camera, allowing someone to adjust the viewfinder to their vision and removing the need to wear their glasses when looking through it. Diopter adjustments cannot compensate for all vision problems, only near and far sightedness can be compensated
DPI – Dots per inch: A measurement of the resolution of a digital photo or digital
device, including digital cameras and printers. The higher the number, the greater
the resolution.
Direct vision viewfinder - sighting device with which the subject
is viewed directly, without the aid of a prism or mirror.
Diode - See Photodiode.
Discharge lamp - light source that provides illumination when an
electrical charge is applied to gas particles in a glass tube. An
example of this device is electronic flash.
Disk drive - A device that reads storage media
Direct print function - The ability to print digital pictures without the need for a computer.
Direct Vision Cameras using an optical viewfinder.
Dish development - method of development used for processing
single sheet, cut film or paper by immersing in a shallow dish of
developer and agitating by rocking the dish.
Dispersion - ability of glass to bend light rays of deferent
wavelengths to varying degrees.
Display - Se monitor.
Distance symbols - symbols used on the focus control of simple
cameras, as a focusing guide.
Distortion - A defect in an image caused by the lens, such as barreling and pincushioning.
Diverging lens - lens which causes rays of light coming from the
subject to bend away from the optical axis.
Docking station - A peripheral device used to connect a
digital camera to a computer
Documentary photography - taking of photographs to provide a
record of social and political situations with the aim of conveying
information.
Dodging - control of exposure in photographic printing achieved
by reducing exposure to specific areas of the paper.
Dolly - frame with lockable wheels, designed to support s tripod,
and allow easy movement around a studio.
Download, downloading – The process of moving computer data from one location to another. Though the term is normally used to describe the transfer, or downloading, of data from the Internet, it is also used to describe the transfer of photos from a camera memory card to the computer. Example: I downloaded photos to my PC.
DPI dots per inch (1 inch = approx. 2.54 cm). A measurement value used to describe either the resolution of a display screen or the output resolution of a printer.
DPOF - Digital Print Order Format. A format introduced by the photo industry that enables images stored on SmartMedia cards to be accessed directly by certain printers and copiers as well as allowing the more simple professional treatment by photo labs.
DOS - Disc Operating System. Usually DOS describes the operating system developed by Microsoft for personal computers.
Dot - The smallest raster element of an image. Many dots together produce one pixel. For example, in the specification "8 bit colour depth", three "layers" of 256 dots each are on top of one another to produce one pixel.
Dot pitch - Used with monitors, it indicates the distance between individual dots. The smaller the distance between dots, the sharper the image. Good monitors usually have a dot pitch of between 0.25 and 0.27 mm.
Double exposure - see Multiple exposure.
Double extension - characteristic of large format cameras which
enables the bellows to be extended to twice that of the focal length
of the lens in use. It is used for close-up photography.-
Download - Describes the process of receiving data, usually via either a →mailbox, the internet or from another device like a digital camera to a PC.
DRAM (Dynamic Random Access Memory) A type of memory that is lost when the power is turned off.
DRAM Buffer Fixed memory used for image processing before the image is stored. Cameras with a burst mode have much larger DRAM buffers. This also makes them more expensive.
driver - The software that allows a peripheral device (camera, card reader, printer) to communicate with and transfer data to a computer
Drop-in-loading - feature in all Advanced Photo System cameras
that virtually eliminates film-loading problems by automatically
accepting the leader less cassette.
Dry down - refers to the amount a print darkens after drying.
Drying cabinet - vented cabinet equipped with suspension clips
for drying films.
Drying marks - marks on the film emulsion caused by uneven
drying and resulting in areas of uneven density, which may show
up in the final print.
Dry mounting - method of attaching prints to mounting surfaces
by heating shellac tissue between the mount and the print.
Dry plates - term used to describe gelatin coated plates in the
days when wet collodion process was still popular.
Driver - A small program that allows the communication between the application program and a certain device, for example a printer or digital camera.
DTP - Desktop Publishing. This refers to the design and illustration of texts and graphics directly on the monitor screen.
DVD-ROM - Digital Versatile Disc. A standard for CD-ROM with a much greater capacity (e.g. 9.4 GB) than a regular CD-ROM.
DX coding - method, whereby films can automatically set the film
ISO speed.
Dyad - pair of complementary colors or any two colors considered
visually harmonious.
Dye coupling - process creating a colored image from the
reaction between by-products of color development and couplers.
Dye destruction process - method of producing a colored image
by partially bleaching fully formed dye layers incorporated in the
sensitive material.
Dye-image monochrome films - black & white negative films
designed for color processing.
Dye sensitizing - defined as all silver halides used in black &
white emulsions are sensitive to blue light. Early photographic
materials possessed only this sensitivity.
Dye transfer print - method of producing color prints via three
color separation negatives. Negatives are used to make positive
matrixes, which are dyed in subtractive primaries and printed in
register.
Dye- sublimation - A printing process where the ink is thermally transferred to printing media. Usually expensive but providing extremely high quality. Thermal dye printers require special paper.
Dye Sub See abow
Dynamism - picture structuring which relates to a sense of
movement and action.
Dynamic range (DR )- is expressed in logarithmic units of optical density (OD)
The range of light intensity in a scene from the brightest area in the scene to the darkest shadows. Measured in Stops of light.
The DR rating of a sensor, scanner, film or print paper indicates how broad of a range of light that the sensor/film/paper/scanner can record at any given
time.
The greater the dynamic range, the more brightness levels that are avialable for that Medium.
read more in raw pipeline by Ted dillard