E to I


Emulsion Light-sensitive coating on photographic film and printing paper consisting of silver halides suspended in gelatin.

Enlargement Any size of print that is larger than the transparency or negative from which it is produced.

Enlarger Darkroom device that projects the image of a negative or transparency onto a piece of photographic printing paper.

EXIF (Exchangeable Image File) Data recorded by many digital cameras as part of the image file. This data automatically records a wide range of information about the picture, including the date and time it was recorded, aperture, shutter speed, model of camera, whether flash was used, number of pixels used, metering mode, exposure mode, exposure compensation used, and zoom setting. This information can be read by certain software. However, the information can easily be lost if the image is subsequently saved in an incompatible file format.

Exposure Amount of light received by a photographic emulsion or imaging chip. Overall exposure is the product of the intensity of the light, the aperture size, and the shutter speed.

Exposure latitude Amount by which a film may be over- or underexposed and still produce an acceptable result when given standard processing. Fast films in general have a wider exposure latitude than slow films.

Exposure latitude will depend on the contrast range of the subject.

Exposure lock Feature found on many automatics SLR cameras that allows the photographer to take a light reading from one part of a scene, lock the reading into the camera, and recompose the picture and shoot. A useful feature when the subject is backlit or when the main subject is either much lighter or darker than the surrounding scene.

Exposure meter A device that measures the amount of light reflected from or falling onto the subject, assesses the film speed, and recommends a shutter speed and aperture to achieve the correct exposure. Can be built into the camera or hand-held; it is also known as a light meter.

Extension bellows Close-up attachment for SLR cameras and view cameras that fits between the camera body and the lens. The bellows unit is made of flexible material and mounted on rails.

Extension tubes Similar in principle to an extension bellows, extension tubes are made of metal in different lengths and can be used singly or in combination to give different degrees of subject enlargement. 

Electronic Flash - Type of flash that discharges an electric current through a gas-filled tube to produce a short burst of bright light. 


Feathering Technique used in digital manipulation to soften the edge of a selection or an effect. A certain amount of feathering is necessary with most selective operations so that the joins between images do not show.

File format The way in which a digital file is saved. A digital image can be saved in a wide variety of file formats – the most commonly-used being TIFF and JPEG. The format dictates which programs will be able to read and open the file. It also dictates the amount of information and the detail that

is stored. Other formats include RAW, GIF, and Photoshop.

Fill-in light Supplementary lighting from a flash or reflector that is used most often to lighten shadowy areas of the subject and reduce overall contrast. Also used to add highlights if the subject is flatly lit.

Film back Preloadable film holder designed for use with a medium-format camera. It is possible to change from black and white to color or from color negative to color transparency film at any time (even halfway through a film), simply by removing the film back from the camera and attaching another, loaded with the appropriate film. A thin, dark plate protects the film from accidental exposure. Digital backs are also available. 

Film plane Plane on which the film lies in a camera. The camera lens is designed to bring images into focus precisely at the film plane to ensure correctly exposed pictures.

Film speed The more sensitive a film is to light, the “faster” it is. The speed of a film is indicated by its ISO number. Each doubling of the ISO number represents a doubling of light sensitivity (for example from ISO 100 to 200 or from ISO 400 to 800). Slow films are in the range ISO 50–100; medium-speed films ISO 200–400; and fast films ISO 800–3200.

Filter Glass, plastic, or gelatin disks or squares that fit over a camera lens or, less commonly, the light source, in order to change the appearance of the finished image.

Filter factor Most filters subtract some of the light passing through them. Through-the- lens (TTL) exposure-metering cameras automatically compensate for any extra exposure required, but for non-TTL and manual cameras, the mount of the filter
may be engraved with a filter factor that indicates the additional exposure that has
to be given.

Fisheye lens Extreme wide-angle lens that produces highly distorted, circular images, sometimes with an angle of view in excess of 200 ̊. Depth of field at every aperture is so extensive that focusing may not be necessary.

Fixed-focus lens Lens that is set to one subject distance from the camera and cannot be selectively focused closer than or beyond the subject. Used on the simplest of cameras, the lens is usually set at the hyperfocal point, which, when coupled with a small maximum aperture, renders most subjects relatively sharp. See also Hyperfocal point.

Flare Non-image-forming light caused by light scattering as it passes through the glass surfaces of a lens, or light reflected from inside the camera body itself.

Flash See Electronic flash.

Flash fall-off Progressive underexposure of those parts of a subject that are beyond the working distance of the flash.

Flash fall-in See Fill-in light.

Flash meter Type of hand-held exposure meter designed to register the very brief burst of light produced by a flash. Some exposure meters can be used in both continuous light and flashlight.

Flash synchronization speed Fastest shutter speed available that ensures the shutter is fully open when the flash is fired.

Flash umbrella Umbrella-shaped reflector that casts a broad area of soft, diffused 

light onto the subject when flashlight is bounced off its inside surfaces. Also known as a brolly.

Flashgun Any type of add-on flash unit. Floodlight Studio light designed to produce a

broad beam of light.

f-number Series of numbers engraved on the barrel of a lens that represent the sizes of aperture available. Moving the aperture ring up one stop (for example from f4 to f5.6) makes the aperture smaller and halves the amount of light passing through the lens. Moving the aperture ring down one stop (for example from f11 to f8) makes the aperture larger and doubles the amount of light passing through the lens. The scale of f- numbers is calculated by dividing the focal length of the lens by the effective diameter of the aperture, so a 110mm lens and an effective aperture diameter of 10mm
would equal f11. f-numbers are also known as f-stops.

Focal length Lenses are most often described by their focal length, measured in millimeters (mm); this is the distance between the optical center of the lens when the lens is focused on infinity, and the focal plane. Zoom lenses offer a range of focal lengths.

Focal plane Plane at which light from the lens is brought into focus. In order to ensure sharp images, the focal plane and the film plane must precisely coincide.

Focal-plane shutter Type of shutter consisting of fabric or metal blinds situated just in front of the focal plane. Focal-plane shutters are normally found only in cameras with interchangeable lenses.

Focal point Point of light on the optical axis where all rays of light emanating from a given subject converge and come into sharp focus.

Focus lock Feature found on autofocus SLR cameras and many compact cameras that allows the photographer to focus the lens on one part of a scene, lock that setting into the camera, and then recompose the picture and shoot. A useful feature when the subject is off-center, as most AF systems focus on anything that is positioned in the middle of the frame.

Focusing Adjustment of the lens-to-film distance in order to achieve a sharp image of the subject.

Focusing screen Glass or plastic screen mounted inside the camera that allows the image to be viewed and focused accurately.

Format Size or shape of a film original, printing paper, or camera viewing area.

f-stop See f-number


Gain Amplification of an electrical circuit. Used in digital cameras as a way of electronically boosting the sensitivity of the imaging chip in lowlight. This allows digital cameras to allow a range of different sensor sensitivities, equivalent to using film with different ISO ratings.

Gamma A method for measuring or setting contrast.

GIF (Graphic Interchange Format) Digital file format that can be used for saving graphics and images.

Grain Exposed and developed black silver halide grains making up a photographic image.

Graininess Term describing the visual appearance of irregular clumps of exposed and developed silver halide grains on films and printing papers. Graininess is most apparent in light-toned areas of an image.

Granularity Qualitative measurement of the degree of clumping together of silver halide grains within a photographic emulsion.

Guide number Measure of the maximum output of an electronic bulb or flashgun that varies according to the film speed used. Lens apertures can be calculated by dividing the guide number by the distance between the subject and the flash. Suppose the number is 40 (metres with ISO 100 film), then at 10m (33ft) the lens would be set at f4, at 5m (16ft) f8, and so on. 


High-key image An image composed predominantly of light tones or colors. See also Low-key image.

Highlights Brightest parts of an image.

Histogram Graphical display – used as a way of depicting and manipulating the brightness, tonal range and contrast of a digital image.

Hot shoe Metal plate usually found on the top of the camera, which is designed to hold a flashgun securely. Electrical contacts on the base of the hot shoe correspond to contacts on the bottom of the flash, so completing a circuit when the shutter is fired.

Hybrid camera A compact digital camera that is designed to handle like an SLR. Combines the fixed lens of a standard compact camera with SLR features such

as adjustable aperture, shutter speed, and color balance. 

Hyperfocal point The nearest point of

sharp focus to a camera when a lens is focused on infinity (for a particular aperture). If the lens is focused at the hyperfocal point, depth of field extends from infinity to a point halfway between it and the camera. 


Incident light The light falling on a subject, as opposed to that being reflected by it.

Infra-red (IR) film Film that is sensitive to invisible infra-red light. IR film is most commonly used for black-and-white photography because it is relatively insensitive to blue. This produces dark, moody images, which can be made even more dramatic by using a red filter. Colour IR film available but less widespread.

Inverse square law Law that states that a doubling of the distance between a subject and a compact light source, such as a flash, results in a quartering of the light illuminating the subject.

ISO Abbreviation for International Standards Organization, the internationally agreed film speed rating system that amalgamated the older ASA and DIN scales.

IX240 Another name for the APS film format.