Photographic Glossary-UVWXYZ

UD
Ultra Low dispersion lens, pls refer to ED, LD sections.

Ultraviolet
The part of the spectrum just beyond violet. Ultraviolet light is invisible to the human eye but strongly affects photographic materials.

Ultra-wide angle lens.
Extra-wide angle lens, usually those with an angle of view greater than 90°. For 35 mm cameras the description usually applies to lenses of shorter focal length than about 24 mm.

Umbrella
Another source of diffusing the light from a flash unit is an umbrella. The use is similar to that of a Softbox except that the diffusion ability is slightly lesser.

Undercolour removal
A separation technique in which black ink is used to replace approximately equal amounts of cyan, magenta, and yellow ink in neutral tones, primarily in the shadows, so as to reduce the total ink coverage.

Under-development
Is a reduction in the degree of development. It is usually caused by shortened development time or a decrease in the temperature of the solution. It results in a loss of density and a reduction in image contrast.

Underexposure
A condition in which too little light reaches the film, producing a thin negative, a dark slide, or a muddy-looking print.

Unipod
Also refer as monopod. A one-legged support used to hold the camera steady. Also see "tripod".

Unsharp masking
A process by which the apparent detail of an image is increased; generally accomplished by the input scanner or through computer manipulation.

Untagged
A Photoshop file that does not contain an embedded ICC profile. To be used in a colour-managed workflow an untagged image must be resaved in Photoshop (with the Embed profile checkbox selected) or tagged with the assign profile command.

Upgrade
To improve some aspect of a computer system. Upgrades include the newest versions of software applications, computer models or peripheral devices. Usually, upgrades are denoted by a version number.

URL
Uniform Resource Locator. A standard addressing scheme used to locate or references file on the Internet. Used in World Wide Web documents to locate other files. A URL gives the type of resources (scheme) being accessed and the path to the file. The syntax used is: Scheme://host.domain;port/path filename.

USB
Universal serial bus. The USB offers a simplified way to attach peripherals and have them recognized by the computer. USB ports are about 10 times faster than a typical serial connection. These USB ports are usually located in easy to access locations on the computer.

USM
( Unsharp Mask ) The term comes from a conventional colour separation camera technique that uses a unsharp photographic mask to increase contrast between light and dark areas of the reproduction and gives the illusion of sharpness.

UV filter
Is a filter which is used to absorb ultraviolet (UV) radiation.

UV
The ultra violet ray. This is beyond the visible spectrum i.e. it's invisible electromagnetic radiation of the sunlight. UV lenses is very expensive, only Nikon has a offering in its Nikkor lens line.

Vacuum back
Is a camera back with a perforated plate through which air is drawn by a pump. A sheet of film is therefore sucked flat against the plate and held firmly during exposure used for special large format cameras such as copying devices where dimensional accuracy is critical.

Vacuum easel
Is a compact printing frame which ensures firm contact between the film and paper by excluding air between the surfaces. Some types are used to hold up the paper flat on the enlarger baseboard when enlarging.

Value
A measure from white to black, the higher the value, the darker the image.

Vanishing point
Is the point at which parallel lines, viewed obliquely, appear to converge in the distance.

Vapor lamp
A lamp containing a gas or vapor that glows with light when an electric current passes through it. Mercury, neon and sodium vapor lamps produce strongly coloured light. The light from fluorescent tubes is closer to daylight.

Variable contrast paper
Is a printing paper in which contrast can be varied depending on the colour of the printing light. This can be altered by using different colour filters.

Variable focus lens
Lens of which the focal length can be continuously varied between set limits. The lens must be refocused with each change in focal length.

Variable-Contrast Paper
Photographic paper that provides different grades of contrast when exposed through special filters.

Vector
An electronic or computer-readable image format incorporating a formulate representation of graphical line art. Vector format is used during the markup process, to keep redlines separate from images and to facilitate easy modifications. This format is also often used during the edit process.

VESA
Video Electronics Standards Association. A 32 bit display or other hardware card.

View camera
A camera with movements in which the taking lens forms an image directly on a ground-glass viewing screen. A film holder is inserted in front of the ground glass for exposure. Also called large-format camera (typically producing images 4x5 inches or greater). Most Large Format cameras are view cameras. Rather than having a prism reflect light from the lens to an eye piece, or be operated like a Rangefinder camera, a view camera projects the image directly from the lens onto a ground glass focusing screen. Once the image is properly focused and composed the film holder is slid into the camera in front of the focusing screen. and the film is then exposed. The lens is then closed, black cover is slid away from in front of the film, the shutter release is tripped and the film is exposed. The black cover is the placed back in front of the film and the film holder is removed. Each negative must be individually loaded in a view camera.

Viewfinder
Device or system indicating the field of view encompassed by the camera lens. The term is sometimes used as a description of the type of camera that does not use reflex or "straight-through" viewing systems and therefore has to have a separate viewfinder. Either an optical or electrical display used to frame in the camera.

Viewing lens
The lens on a camera through which the photographer's eye sees the subject.

Viewpoint
Location of the camera relative to the subject.

Vignetting
Is a printing technique where the edges of the picture are gradually faded out to black or white. It also refers to a fall off in illumination at the edges of an image, such as may be caused by a lens hood or similar attachment partially blocking the field of view of the lens. Underexposure of image corners produced deliberately by shading or unintentionally by inappropriate equipment, such as unsuitable lens hood or badly designed lens. A common fault of wide-angle lenses, owing to reflection cut-off, etc. of some of the very oblique rays. May be caused in some long-focus lenses by the length of the lens barrel.

Vintage
A photograph printed within a very few years of the date when the negative was made. Prints made recently from original negatives that are old are called modern prints.

Virtual memory
Disk space on a hard drive that is identified as RAM though the operating system, or other software. Since hard drive memory is often less expensive than additional RAM, it is an inexpensive way to get more memory and increase the operating speed of a application.

Virus
Describes a part of a computer program that automatically duplicates itself, usually resulting in the damage or destruction of software and/or data. A virus can make a computer "crash".

Visible light
The portion of the electromagnetic spectrum that the human eye can see.

Visible spectrum
The electromagnetic spectrum of visible light; red, orange, yellow, green, blue, indigo, violet.

Warm colours
Are any colour which, by association suggest warmth, such as red, orange and yellow.

Washing aid
A chemical solution used after fixing and washing the film or paper. It shortens the washing time by converting residues from the fixer into forms more easily dissolved by water. Also called hypo clearing agent.

Washing
Is the final part of the processing cycle, which removes residual chemicals and soluble silver complexes from the emulsion.

Water bath
Are large water filled containers used to maintain processing trays, tank or chemicals at the correct temperature.

Watermark
Bits altered within an image to create a pattern which indicates proof of ownership. Unauthorized use of a watermarked image can then be traced.

Wavelength
Describes the distance from wave-crest to wave-crest between two corresponding waves of light in the electro-magnetic spectrum. Wavelength are measured in nanometers (nm) and Angstrom units (A).

Web Optimization
When a photo or graphic is produced its file size is often too large for use on a website. Optimization is achieved by reducing the size of a large file by converting it to GIF or JPEG format.

Web Safe Colours
Colours in which will display accurately and consistently on every version of internet browser (Internet Explorer, Netscape Navigator, etc.) or computer platform (PC or Mac). There are 216 web safe colours.

Wetting agent
A chemical solution used after washing the film. By reducing the surface tension of the water remaining on the film, it speeds up drying and prevents water spots. Kodak version of this is called Photo-flo.

White point adjustment
An adjustment made that will determine the amount of highlight detail in an image. It is considered proper to set the white point so that the lightest part of an image will only just have zero detail.

White balance
The perceived colour of an object is affected by the colour of the lighting under which it is viewed. The human brain is able to detect and compensate for such changes in perceived colour. As a result, a white object will look white to humans whether viewed in sunlight or under overcast skies, or indoors under incandescent or fluorescent lighting. A digital camera must emulate the human brain and adjust colours accordingly to lighting so that colours appear white when viewed directly also appear white in the final photograph. This adjustment is called “White Balance”. Most video systems use a "white balance" to aid in overcoming colour problems created by adverse lighting conditions. The colour balance assumes that under normal conditions, that if a white object can be made to look white, then the remaining colours will be accurate too. If the original lighting is not close to the proper colour temperature (typically daylight), the "white balance" may reproduce white at the expense of other hues. Most digital cameras feature automatic white balance, this means that the camera looks at the overall colour of the image and calculates the best-fit white balance, however these systems are often fooled (especially if taking a photograph dominated by one colour, say green). Modern "prosumer" digital cameras also allow "white preset" which simply means measuring the white point from a white sheet of paper or card (or nearby wall), the camera will then record that temperature and use it to correct all images until you reset it.

White light
Light containing equal amounts of the primary additive colours of light. The human eye sees this light as colorless.

White point
The results of combining the additive primary colours, Red, Green, Blue.

White
The result of combining the additive primary colours (Red, Green and Blue).

Wide-Angle Lens
A lens that has a shorter focal length and a wider field of view (includes more subject area) than a normal lens. Also can explained as a lens whose focal length is shorter than the diagonal of the film frame; in 35mm photography, lenses shorter than 50mm; also referred to as a "short" lens.

Wide-angle lens
In 35mm format cameras, lenses with a focal length of approx. 35mm are called wide-angle lenses.

Working aperture
The widest aperture at which an acceptable image can be achieved.

Working distance
The distance from the front of the lens surface to the subject. The more frequently used term "shooting distance" refers to the distance between the subject and the film plane.

Working solution
A chemical solution diluted to the correct strength for use.

Worm
Write Once Read Many. Most common to optical disks. Worm refers to data storage that cannot be change once written. However, it may be read as many times as desired.

Wrong reading image
An image that is backward relative to the subject (a mirror image).

WS ( Watts per second)
For flash mode, the measurement of electrical energy in the flash.

WS
Watt per second. For flash mode, the measurement of electrical energy in the flash

WWW
World Wide Web. An interconnected network of electronic hypermedia documents are marked up in Hypertext Markup Language. Cross references between documents are recorded in the form of URLs.

WYSIWYG
An acronym for What You See Is What You Get. Refers to the ability to output data from the computer exactly as it appears on the screen.

X (setting)
Electronic flash units fire virtually instantaneously and reach full brightness immediately. Therefore no time delay is required. Also refer as X sync. Real time setting that causes the flash to burst in synchronises or instantaneously as the shuttle open up. For older manual camera, the X synch speed usually refers to the maximum speed that the camera can have its shuttle curtain open long enough to synchronise with the flash. In fact, if there is a time delay, the electronic flash may be all over before the shutter gets open. To fire electronic flash with a focal-plane shutter, the switch in the camera is closed at the instant the first curtain of the focal-plane shutter reaches fully open-called X synchronization.

X ray film
is spectral sheet film for radiography, having a thick emulsion coated on both sides of the support to increase the absorption of X rays.

X ray
are electromagnetic radiations beyond ultraviolet which, when passed through a solid object and allowed to act upon a sensitive emulsion, form a shadow image of the internal structure of the object.

X setting (X sync)
is the setting that causes the flash to burst in synchronization with the shutter. For some manual cameras, the X synch speed refers to the maximum speed that the camera can synchronize with the flash.

X Sync Terminal
Electronic flash units are available which mount on the hot shoe and are triggered by the electrical contact in the shoe. Other types use sync cord which connects to the sync terminal on the camera. also referred to PC Terminal section.

Xenon
is a rare gas sometimes used with electronic flash tubes and enclosed arc light sources.

Xerography
is a photographic process which uses an electrically charged metal plate. On exposure to light the electrical charge is destroyed, leaving a latent image in which shadows are represented by charged areas. A powdered pigment dusted over the plate is attracted to the charged areas, producing a visible image.

Xography
is a system of photography which produces prints and transparencies with a three-dimensional effect. A cylindrically embossed lenticular screen is placed in contact with the film and a shutter behind the lens is arranged to scan the subject during exposure.

Yellow
A subtractive primary, and one of the four process ink colours; yellow reflects red and green light, and absorbs blue.

Zip
To compress a file or files into one file. Commonly used to reduce the size of a file to speed up transmission over the Internet.

Zirconium lamp
is an arc lamp used in powerful enlarges and projectors.

Zoetrope
is an early device for creating illusion of continuous motion. A sequence of still pictures was viewed so quickly through slits in a rotating drum, that the images appeared to merge.

Zone focusing
is a method of focusing the lens so that the depth of field extends over a preselected range of distances.

Zone system
is the method of determining exposure and development required for individual scenes, invented by Ansel Adams. It is based on analysis of subject luminosities in terms of ten gray tones, labeled zones 0 through X and previsualizing them as print densities. By measuring each subject luminance with a hand meter it is possible to determine how much the range of values must be contracted or expanded by negative development control to give the required values in the print.

Zone system
A method of planning film exposure and development to achieve precise control of tones in a print. Pioneered by photographers such as Ansel Adams and Minor White. To some people the Zone System is the only method that one should use to meter a scene. The zone system involves the creation of 11 zones numbered 0 - 10 where 0 is the blackest black and 10 is the whitest white. A zone 5 is what a grey card should render, or 50% white and 50% grey, and which reflects 18% of the light falling on the object. By using a gradient scale between 0 and 10, each zone change being equivalent to one f-stop, a photographer should be able to meter the scene to be properly exposed for any portion of the scene by realizing that a camera meter will meter any scene to be a zone 5. Example: Human Caucasian skin is approximately a zone 6. If a light meter metering the skin indicates that the proper shutter speed is 1/ 125 at f:4 then to properly expose the skin one would need to overexpose by on stop, shoot at 1/ 60 at f:4 and the skin should be exposed at the proper tone. If one were to shoot at the indicated settings the metered object should render a zone 5, or mid grey, when printed.

Zoom, Optical vs. Digital
Whereas an optical zoom uses the optics (lens) of the digital camera to move you closer to your subject, a digital zoom simply uses the existing image and enlarges it digitally. Enlarging the image digitally reduces picture quality, and should therefore usually be avoided. However, a judicious use of digital zoom may sometimes yield images that are of quite acceptable quality. So, use with caution. What is important when comparing digital cameras is the optical zoom. Digital zoom can always be achieved later in an image editing software, such as Photoshop, so should not really be a determining factor when choosing a digital camera.

Zooming
Enlarging a portion of an image in order to see it more clearly or make it easier to alter. Opposite of zoom-out, which is useful for viewing the entire image when the full image is larger than the display space.