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Glossary "F"

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The lens focal length divided by effective diameter of the aperture gives the f/number that's used to indicate the aperture value. Each full f/number, also called a stop or f-stop, halves or doubles image brightness and some lenses can also be controlled in half or third steps. The most common f/numbers are 1.4, 2, 2.8, 4, 5.6, 8, 11, 16 and 22. They are usually preceded by an "f". The larger the f-number, the smaller the lens opening. In the aforementioned series of numbers, f/1.4 is the largest opening and f/22 the smallest. The smaller stops (larger f numbers) give the greater depth of field in a photograph, and vice versa.
A film that produces a photograph with significantly different colours than our eye sees, such as Ektachrome Infrared.
A modem that can also be used to send or receive fax messages.
A digital method of softening the edge of a selection or brush to ensure a less sharp edge or seamless blend when cloning, painting and pasting images.
A printing paper that doesn't have a resin coated surface. It takes much longer to wash and dry but the results can look better and it has better archival qualities.
A folding view-camera that's usually made of wood or light metal for use on location.
As you look through the viewfinder of an SLR it should give you as near as possible what will appear in your image. Because of the design, position and size of mirror/pentaprism, etc., this is not always possible and you often see less than 100%. The higher this figure is, the more accurate the results will be. It's usually only professional cameras that give 100% accuracy.
A distance, or angle, measure given by binocular manufacturers that's similar to angle of view on a lens. It's usually indicated in degrees or as a width in meters at 1000m. A pair of binoculars with, for example, 6 or 105m at 1000m indicates that you will see a 105m span when you're viewing a subject that's 1000m away. A wider field of view is better for looking at wider expanses - birds in flight, horse racing, starry skies, etc.
Common name for an electronic document or digital image.
The way that a file is saved so it can be seen and is compatible with other applications/computers. Digital images are saved in a format such as TIFF, EPS, JPEG, PNG, BMP or Photo CD that can then be opened on different computers.
The amount of data held in a file determines its size. High resolution digital images can be 50 megabytes, for instance, while a text document may only be a few hundred kilobytes or less. Images can be compressed to save space, and folders of text and pictures can be grouped and reduced in size using programmes such as Stuffit, WinRAR or WinZip.
A way of reducing harsh contrast by adding light to darker or shaded areas of the subject using a reflective material or flash.
The light-sensitive material used in most non-digital cameras to record an image.
This is used to describe the area of a film used by a camera to record a photo. A 35mm format camera records a 24x36mm image on the film. Medium format cameras record anything from 6x4.5cm to 6x17cm on 120 and 220 roll film. When choosing a medium-format some photographers prefer the square 6x6cm format because it offers an alternative shape to the conventional oblong, but also saves you having to think in a portrait or landscape way. The cropping can be done later when printing the results. As the format increases, potential quality improves, while the number of pictures that can be recorded on a roll of film decreases. You can shoot 15 pictures on a 6x4.5cm camera, 12 on a 6x6cm camera and 10 on a 6x7cm camera and just 4 on a 6x17cm camera.
A two-sided frame that holds a sheet of film on either side for use with large format cameras.
The area in the back of the camera where film is positioned during exposure.
A unit used to record digital images onto transparency or negative film.
A peripheral that scans slides or negatives and converts them into high resolution digital images.
Used to indicate the light sensitivity of a film as ISO. Digital cameras also use the ISO rating to indicate the CCD sensitivity.
Most cameras now set the speed film automatically using DX coded film cassettes, but if there's a dial you can usually override. This can be used to uprate a film or adjust to suit your shooting preferences or to bring an out of calibration exposure meter back in line.
The range of films that can be used by the camera. Most modern cameras set this speed automatically using DX coding, some have manual settings that have a slightly wider acceptance range. The range quoted is for the maximum that can be used.
A rotating set of four icons on the base of an APS film cartridge that indicates what stage the film is at unexposed, partly-exposed, fully-exposed but not processed and processed.
Glass or plastic item that goes in front of the camera or enlarger lens to either absorb and remove selected wavelengths of light or add special effects such as soft focus, starbursts or multiple images. There are different ways of attaching filters, for instance screwing a round filter in front of the lens, or sliding a square or rectangular filter in a filter holder which is attached to the lens with an adapter ring.
Part of a software programme or plug-in for a programme that is used to alter the appearance of a digital image. Countless options are available to distort, blur, sharpen or add artistic effects.
Indicates the amount the unfiltered exposure should be increased when an optical filter is attached.
Most SLR cameras, some digital and a few compacts have a threaded ring at the front end of the lens. This is used to attach coloured and special effect filters as well as other accessories to alter the light that reaches the film. The diameter of the lens' filter thread is measured in millimetres. Stepping rings can be bought to allow one size filter to fit on a different size thread. It's better to step up (use a filter with a larger thread than the lens) to avoid corners being cut off resulting in dark edges to your pictures. Buying advice: If you're considering buying a camera for use with a particular lens accessory, make sure you can either fit the accessory direct to the camera lens or at least adapt it to fit.
An automatic exposure mode which selects a high ISO sensitivity and shutter speed of about half a second, which is perfect for capturing the colours of a fireworks display.
Extreme wide-angle lens that gives 180 degrees coverage and is uncorrected for curvilinear distortion so you produce a heavily distorted photograph. If the photo turns out to be rectangular or circular, and how distorted it looks, depends on the lens and the camera. There are basically two kinds of fish-eye lenses for photography: 1. Lenses that produce a circular image, typically 8 or 10mm lenses, used on 35mm cameras or full-frame digital cameras. They produce a circular image with dark corners (due to most photos being rectangular). A similar lens is available for digital cameras with a so-called "cropped sensor". To achieve the same circular effect, it's a 4.5mm lens. 2. Lenses that produce a rectangular image. These lenses enlarge the image to cover the whole rectangular frame of a photograph. They are typically 15 or 16mm lenses. On a 35mm or digital full-frame camera they produce rectangular but still heavily distorted images without dark corners. The same lenses on a digital camera with a cropped sensor will still have a distorting effect, but less so. Fish-eye lenses used to be prime lenses only, but one company has gone so far as to produce a 10-17mm fish-eye zoom lens. This lens still produces distorted, curvy images, but zooming in lessens the distortion.
(Not be confused with Fixed focus lens!) A lens that only has one focal length (as opposed to a zoom lens). A fixed focal length lens (also called 'prime lens') will often have good brightness, contrast, and be optically well-corrected. For that, it doesn't need any special glass or aspheric lens elements. Fixed focal length lenses are always superior to zoom lenses if they're made with the same optical materials and standards. They usually offer a wider maximum aperture than zoom lenses. They're often preferable for indoor shooting, but are also favourite choices as long telephoto lenses used for wildlife, sports and news photography.
A low-cost lens that doesn't have a focusing ring. Found in very basic cameras. The lens is set to a distance of around three meters and relies on the depth of field to bring everything from about one and a half meters to infinity. The quality is always a compromise over a lens with adjustable focusing.
Chemical used after developing and before washing to remove remaining light-sensitive halides by converting them into soluble salts. An image becomes stable to light once it's fixed.
Keys on many keyboards that can be assigned to perform additional tasks such as short cuts to print, e-mail or save pictures/documents.
Flare is unwanted light reflecting within a lens or camera that reduces contrast and creates bright streaks or patterns on the image.
Many cameras now have a built-in flash that is used to take pictures inside when the light levels are low. Most cameras will have an Auto mode and there are usually several other modes including, Red eye reduction, Off, On, Slow sync.Most SLRs and some compacts have the option of attaching an external flash on an accessory shoe. Some have a sync socket so you can attach a studio flash off the camera for more controllable results. Buying advice: The flash range is often quoted and ones with more power will allow well-exposed pictures to be taken at greater distances. Having several modes increases the camera's versatility. If you would like to use studio flash you can fire heads remotely using your camera's built in flash and a slave unit, but watch out on digital cameras - the flash may not be synchronised correctly. It's better to use a camera with a sync socket. The most useful feature of an auto camera is Flash Off so you can avoid flash when you want to shoot in low light and Flash On to force the flash to fire to get good fill-in light in contrasty conditions.
A time measure taken from a flash between it reaching 50% of its peak value to the point when it has diminished to the same value.
A type of memory that can hold data without needing power. It's used in SmartMedia and CompactFlash cards so photographs are safely stored when the camera is switched off.
A meter used to measure the light that is emitted from an electronic flashgun. The meter suggests what aperture should be used to obtain a correct exposure. Some meters are purely for flash, others are multipurpose.
Many cameras now have a built-in flash that is used to take pictures inside when the light levels are low. The camera detects when flash is needed and automatically fires it, there are usually several other modes to increase the flash's versatility. Red eye reduction fires a pre-flash to prevent large red eye pupils appearing. 'Off' turns an automatic flash off so that the camera can be used with a long shutter speed for night photography. 'On' forces the flash to fire as a fill-in for daylight pictures that have harsh shadows or to illuminate a close subject in a night scene. Slow sync fires flash and records the ambient exposure, which is great for creating image trails and creative subject movement.
Flash units often have a range of settings that controls the amount of flash emitted. With portable on-camera flash this is normally controlled automatically by either the camera or a sensor on the flashgun. Studio flash are often less sophisticated and have a slider or switch offering half or quarter power. Some of the more expensive models can be adjusted more accurately though a greater range of stops.
An electronic flash has a maximum distance that it is capable of illuminating. There's also usually a close point where it will start to become too bright and overexpose the subject. The distance from the closest to the furthest point that it can illuminate is the flash range. The range can be increased by using a faster film or more sensitive CCD, and reduced by diffusing the light source using ND filters or material. The range quoted is usually based on using ISO 100 film or a CCD with equivalent sensitivity. APS cameras are, for some reason, quoted using ISO 200 film.
A socket on the camera used to plug-in an electronic flash gun cable so that the flash can be triggered at a distance from the camera.
The maximum shutter speed that can be set when using electronic flash. You can use shutter speeds below this setting but ones above will make some of the picture dark because the shutter would have partially closed before the flash had fired.
Old type of flash light that ignited by simple battery/capacitor system and was used once.
A technique used by advanced printers to lower contrast by giving a brief exposure to the sheet of printing paper either before or after the image has been exposed to it.
Term given to a photograph that lacks contrast because of its minimal tonal range.
Computer peripheral with a glass plate that you lay photos prints, artwork or transparencies on to scan and convert into digital images. Most models have an a4 scanning area and cover A3.
A flexible magnetically-sensitive disc that's held inside a 3.5inch square hard plastic case. It has a storage capacity of 1.4Mb which is ideal for transporting text or low resolution or highly compressed digital images. The format is gradually becoming antiquated as advanced storage options such as removable media compete.
A neon-like glow that's radiated by some substances when exposed to ultra-violet light.
Indicates the magnification and angle-of-view of a lens. The human eye sees things roughly the same as a 43mm focal length of a lens for a 35mm camera. Anything shorter is classed as a wide-angle, while longer focal lengths are telephoto. Because of the comparatively small size of the CCD in a compact digital camera it has a standard focal length of between 6mm and 8mm while a medium-format camera is around 80mm.
The area behind the lens where light is gathered to form a sharply-focused image. It's here where the film or CCD is placed.
A position where rays of light converge through a lens to create a sharp image. (This position is sometimes also called an "image point".) "To focus" means adjusting the distance setting on a lens to create this image point, which defines the subject sharply. With a photo camera, this is done by moving the lens physically towards or away from the film or sensor, or by moving the front of the lens towards or away from the rear part of the lens, which alters the focal length. (There are exceptions to this method: Contax, for instance, has a system where the autofocus operation actually moves the film and not the the lens.) When something is "in focus", it's sharp.
With focus stacking (also simply called 'stacking') one combines multiple images in a software program, each image with a slightly different focus, in order to increase the depth of field or the sharpness of an image. It is mainly used for astronomy, macro or micro photography.
The action of adjusting the lens so that the subject appears sharp on the film or CCD. Most cameras now have automatic focus (AF), some have manual focus override (MF) and some have a fixed focus (F) lens that ensures things from about 1.5 meters to infinity are relatively sharp. A few cameras have a power focus (PF), which is a manual method but using a motorised focusing ring. Buying advice: Autofocus is essential if you want to use the camera effortlessly, but occasionally the system is fooled, so make sure the camera has a focus lock or infinity setting or, better still, full manual control. Also check what the closest range is. Some only go down to about one meter which is useless if you want to fill the frame with a small object such as a flower or piece of jewellery.
The ring used to adjust the lens so that the subject appears sharp on the film or CCD. Most cameras now have automatic focus (AF), some have manual focus override (MF) and some have a fixed focus (F) lens that ensures things from about 1.5 meters to infinity are relatively sharp. A few cameras have a power focus (PF), which is a manual method, using a motorised focusing ring. Lenses with a ring that allows a good grip make it easier to adjust and focus manually.
Indicates the distance from the film plane to the subject, usually in both feet and meters. Some digital cameras can use lenses originally designed for analogue/film cameras, and in case of digital cameras with cropped sensors the owners should take the crop factor into account when using the focusing scale.
Indicates the number of positions a lens stops at when focused. In theory, lenses with more stops offer a greater stage of focusing zones for sharper results, but in practice this is difficult to see when using a compact camera with more than 30 zones.
Where you accidentally expose an unprocessed film to light and create an unwanted veil of density. Sometimes cameras have a light leak around the sealed film chamber and the fogging appears as orange streaks spreading across the film.
A place on the computer where programs and files can be stored in an organised way. Computer users who were used to older computers and operating systems than the current ones, often refer to folders as 'directories'.
Typeface or text style used in word processing, desk top publishing or image captioning.
A technique which, through optical illusion, makes an object appear farther, closer, larger or smaller than it actually is. With this technique, the photographer manipulates our visual perception by using scaled objects, as well as the correlation between them and the vantage point of the viewer or the camera.
Format (noun) is used to describe the area of a film used by a camera to record a photo or the way a digital file is saved (see film format). Or it is the way that a file is saved so that it can be seen and is compatible with other applications and/or certain computers (see file format). 'To format' (verb) is to lay-out or organize text on a computer, or to prepare a digital disk for use with a certain type of computer.
The Foveon X3 direct image sensor is a new technology that works like film. Foveon pioneered the development of the direct image sensor using advanced developments in semiconductor design, image processing, and signal processing. Their X3 sensor directly captures red, green, and blue light at each point in an image during a single exposure. Similar to the emulsion layers used in colour film, Foveon X3 image sensors have three layers of pixels. The layers of pixels are embedded in silicon to take advantage of the fact that red, green, and blue light penetrate silicon to different depths - forming the first and only image sensor that captures full colour at every point in the captured image.
Flash synchronisation that was once used with focal plane flashbulbs.
Hardware used to pull one frame from a movie sequence taken with a camcorder and digitise it. Software can also be used with digital camcorders to grab an already digitised picture.
A method of transferring files and data over a network. You use an FTP program to upload web pages created on your computer to a server so they can be accessed on your web site.
An imaging sensor with the same size as film used for the respective format of camera. See also Crop factor and APS-C.