Glossary of Photo Terms



EF  – Electro-Focus
Canon lens designed for their EOS cameras, both film and digital.

EF-S – Electro-Focus – APS-C only
Canon designation for a lens designed for the smaller image circle required by an APS-C sized sensor. Cannot be used on a film or full-frame camera.

ELD  – Extra Low Dispersion
A type of glass that refracts all wavelengths of light even more equally than LDglass to reduce Chromatic Aberration. 

E-TTL – Evaluative Through The Lens (Also ETTL II)
This is Canon’s term for their advanced electronic flash technology. It allows the camera to evaluate the exposure for the flash by using a pre-flash and measuring the exposure before firing the main burst.
EV – Exposure Value -A scale denoting relative illumination as it relates to photographic exposure with EV 0 equaling 1s at f/1.0 (or 2s at f/1.4) at ISO100. A typical indoor scene would be around EV 5-7 and outdoors on a sunny day would be EV 15.
EVF – Electronic Viewfinder
Camera viewfinder that uses video imaging to display the image directly from the camera’s sensor in real-time.

EVIL – (also ILC), Mirrorless
Electronic Viewfinder, Interchangeable Lens. A early name for the class of cameras that use a larger (DSLR-sized) 4:3 or APS-C sensor in a compact camera body with an electronic viewfinder linked to the camera’s sensor. This eliminated the mirror box and theoretically allowed for a much smaller camera body with more compact lenses than those for a DSLR. The Micro Four-Thirds standard was based on this concept but Sony and Samsung used APS-C sensors in their early models. Nikon chose the much smaller CX (1″) sensor for their first entry (now discontinued).

EXIF – Exchangable Image File Format
Exif file data is embedded in JPEG files by the camera to record information about exposure, focal length, time of day, camera model and many other specific bits of information. Most editing programs and image viewers can access this data and some can add additional information like copyrights geo-location coordinates and comments.

f/-Stop – Also: Aperture
The lens f-number (usually called an  f/-stop) is a ratio determined by dividing the diameter of the hole (aperture) in the lens body that lets light in by the focal length of the lens.  Since the ratio value gets larger as the diameter decreases, a lower f-number allows more light in than a larger one.

FF – Front Focus
An out-of-calibration condition where the camera’s focusing system indicates focus, but the lens is actually focused slightly In front of the target.

FF (again) – Full Frame 
Refers to imaging sensors that are approximately the same size and aspect ratio as the standard 35mm film frame. 36mm × 24mm.
Fill Flash – Fill-in Flash -This is a technique for adding a small amount of flash to a scene to balance the subject against the ambient light. Often used to compensate for back-lighting or to brighten up shadows on subjects that are lit from the side or in bright sun.
Fisheye – Fish-eye -Fisheye lenses got their name from the simple fact that the front element of the lens bulges out to the point of being almost a half-sphere, making it look like a fish’s eye.  These are specialized wide angle lenses that usually provide a full 180° field of view. Because no effort is made in the design to correct for spherical distortion, the images taken with these lenses are very distorted with straight lines curved heavily outward, especially toward the edges. Originally developed for taking pictures of the entire sky to record cloud formations for meteorological studies, they are now used to make images where the extreme distortion can provide an artistic effect.

FL – Focal Length
Technically, the distance from the nodal point of a lens to the focal plane when the lens is focused to infinity. Practically, it denoted the relative magnification of a lens with approximately 50mm equaling what the human eye sees, or 1x. Longer lenses magnify (300mm = 6x) and make objects seem closer. Shorter lenses give a wider view (24mm = .5x).
Focus Peaking – Same as Peaking -On advanced video and still cameras, focus peaking superimposes a dense pattern of bright dots over areas of high contrast corresponding to areas of the image that are in sharp focus. This is especially helpful when focusing manually.

Four Thirds – Also 4/3
This is a standard developed jointly between Kodak, Olympus, Panasonic and through Panasonic, Leica in 2006 to provide a designed-for-digital format that would allow for compact, fully-functional DSLRs that uses a defined sensor size and could interchange lenses between manufacturers via a standard mount. The name comes from the agreed-upon standard sensor’s aspect ratio that is 4:3 which is similar to most P&S cameras rather than a typical DSLR which has a 3:2 aspect like 35mm film. This format was short-lived and was superseded by the Micro Four Thirds format in 2008 which used the same mount but removed the necessity for DSLR mirror box and replacing it with live-view on the LCD or an EVF for composing.

FP – Focal Plane
The fixed plane in a camera’s design where the image transmitted through the lens is to be rendered in focus. The sensor or film is always mounted at the Focal Plane. On most advanced cameras it is identified on the top of the body with a ɸ symbol.

FPS – Frames Per Second
The number of images a camera captures every second, whether shooting stills in bursts or movies.

Frame Rate – Same as FPS -The number of images a camera capture every second, whether shooting stills in bursts or movies.

FTM – Fulltime Manual Focus -Camera/lens setting that turns off autofocus completely and requires the lens to be focused manually. Old reference.

G – Grrrrrreat! (?)
Designation given to the highest tier of Minolta lenses. Now used to designate the premium non-Zeiss Sony lenses.

G – Gone! (?)
G-type Nikon lenses are designed for use with Nikon SLRs aand DSLRs where aperture is controlled from the camera body. The lack of an aperture ring limits the backward compatibility with some older film SLRs.

GB – Gigabyte
Equal to 1,073,741,824 bytes (closest exponent of two to one billion). Unit of measure commonly used to denote the capacity of computer-related media such as memory chips or discs.

GIF – Graphics Interchange Format (.gif)
Developed in the late ’80s by a team at CompuServe to allow for smaller file size for images. Intended for images containing logos consisting largely of solid areas of color, it only supports 256 colors per pixel and is poorly suited for large complex images. It supports transparent areas as well as simple animation. It is also almost universally viewable by any program that uses graphics.

HDR – High Dynamic Range
A technique that uses two or more bracketed exposures of the same subject and blends them to create a single image that covers a wider Dynamic Range that the camera is capable of in a single shot. The result is an image that retains more detail in both the highlight and shadowed areas to more closely represent what the human eye sees. It also refers to displays such as computer monitors and TVs that can display such images to good effect.

HS – High Speed
Minolta designation for lenses from their film era that were redesigned to take advantage of later model’s faster focusing capability.

HSM  – Hyper-Sonic Motor
Sigma term for their in-lens motor technology

Hybrid AF – Hybrid Autofocus
A type of autofocus that uses both phase detection and contrast detection simultaneously. This is a very effective method since the phase-detection can provide the gross directional information that can be refined by the contrast-detection segments when the lens gets close to being in focus.