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Photographic Glossary (Q to Z)

The meaning of the more common terms and phrases used in photography…

A

Abberation
Causes completely blurred images. There are six types of aberrations: spherical, coma, astigmatism, curvature of field, distortion and chromatic.

AF (Autofocus) Lock
Locks the focus once the subject is in focus.

AF Sensor
The sensor used to detect the focus in cameras equipped with autofocus operation.

APS
Advanced Photo System. A photographic system that can be printed in three formats: High Definition, Classic and Panoramic. Most APS models are point and shoot cameras.

Aperture
Sometimes called “F-stop”. The adjustable opening in a camera lens used to control the amount of light reaching the film. The size of this hole is called the f-stop.

Apochromatic
Refers to lenses designed to correct for color aberrations. Usually used in telephoto lenses that have large maximum apertures. (See Chromatic Aberration.)

ASA
Abbreviation for American Standards Association. In conjunction with a number, e.g., ASA 400, refers to film "speed" or sensitivity. The higher the number, the more sensitive the film.

Aspherical
Not a continuous curve. Refers to elements in lenses which have been designed to compensate for distortion by having different curves on individual elements. Allows for a more compact lens.

Astigmatism
An optical defect that causes light rays from an off-axis point to form images at different positions.

Av mode (Aperture Value)
A setting on an SLR camera allowing you to dictate the F-stop of the lens (aperture) and let the camera`s metering system select the appropriate shutterspeed setting.

 

B

Backlighting
Light coming from behind the photo subject. Can cause underexposure of the main subject with autoexposure systems.

Bellows
Accordion-like device on cameras that allows the lens to move toward or away from the film-plane. Usually used for close-up or macro work.

Bit Depth
The term "bit depth" is used to describe the number of bits used to store information about each pixel of an image. The higher the depth, the more colours that are available for storage.

Black and White film
Light-sensitive film that, when processed, produces a black and white, negative image. The resulting "negative" is projected onto light-sensitive paper to make black and white photographic prints.

Bleed
Running of colours along or off the page when a photograph is printed.

Blur
Unsharp. Caused by inaccurate focus or excessive movement of the camera or subject.

BMP (Bitmap)
A windows computer file format for image files.

Bracketing
This is the custom of altering exposure settings to ensure accurate exposure of a subject; e.g., exposing "one stop under" and "one stop over".

Bulb
Shutter speed setting where the shutter stays open as long as the shutter release is depressed. Usually indicated by a B on the shutter speed selector.

 

C

C-41
The process used to develop colour negative film. Some types of Black and White negative film can be processed in this way also.

Cable Release
A cable device for releasing the shutter. Usually used for slow shutter speeds when the camera must remain absolutely still.

CCD (Charged Couple Device)
A photosensitive microchip, essentially the “film”, found in digital cameras.

Chromatic Aberration
A type of image distortion that usually appears as a rainbow on the edge of objects towards the outside of an image. Occurs when light rays passing through a lens focus at different points, depending on the light wavelength. An "apochromatic" lens corrects for this problem.

Chromagenic Film
Black and white film made for processing in C-41 color chemicals.

Color-negative Film
Light-sensitive film that, when processed, produces a coloured, negative image. The resulting "negative" is projected onto light-sensitive paper to make photographic prints.

Continuous AF
Used to allow the camera to continue focusing as long as the shutter release is slightly pressed. This allows an AF camera to take a picture even if the picture is not in focus. Used for taking pictures of fast moving subjects. Also known as "Predictive Autofocus".

Contrast
The difference between light and dark values. Usually refers to the progression between black and white with less grey being described as High Contrast. Lots of   shades of grey can be described as low contrast.

Copyright
Protection provided by the laws of all countries to the authors of original works. This includes literary, musical, artistic and other intellectual works and is available in published or unpublished form. Allows the author to authorise the use (usually for payment) of copyrighted material by non-copyright holders.

Crop
To cut out parts of an image while enlarging or reducing the size of the print.

Curvature of Field
When light rays passing through a lens tend to focus on a curved plane rather than a flat plane resulting in images that are not in focus in the centre of the image at the same time as the outside of the image.

D

D-Type Lens
A lens design by Nikon that provides distance information as part of flash and ambient light exposure calculations.

Darkcloth
Dark material used to cover the photographer's head and the ground-glass viewing screen on large format cameras.

Darkroom
A lightproof room for processing and printing photographic materials.

Dedicated Flash
Electronic flash designed to work with the meter and exposure system of a specific make of camera.

Depth of Field 
The distance between the nearest and farthest points in a photograph that are in focus. Depth of Field can vary according to lens focal length, aperture, camera to subject distance.

Developer
Chemical that converts the silver halide on film to a visible, black image.

Diaphragm
The opening of a lens that allows the light through to the film or image sensor. Also known as Aperture.

Diffraction
Bounced light. Light "refracts" off opaque materials softening and blurring an image.

Diffused Light
Soft light – a good example is daylight through the clouds.

Diffuser
Material that softens and "diffuses" light in order to soften the edges in an image.

Dispersion
Light rays of different wavelengths deviate different amounts through a lens causing a rainbow effect around points and edges.

Distortion
Optically, where straight lines are not rendered perfectly straight in a focused image. The two types of "distortion" are barrel and pincushion.

DX Coding
Type of bar coding used to electronically communicate film speed (ISO) to the camera.

 

E

ED (Extra Low Dispersion Glass)
Lens type by Nikon that has at least one element made from Extra Low Dispersion glass, which improves sharpness in the image.

EF Lens
Type of Autofocus lens designed by Canon for use with EOS cameras.

Emulsion
The light sensitive, chemically active surface on photographic film and paper.

Enlargement
A photographic print made by "enlarging" an image from a piece of film or digital image.

Exposure
The combination of shutterspeed and aperture (F-stop) that allows light through the lens onto the film/or camera sensor to allow a photograph be recorded.

Extension Tubes
Hollow metal tubes used to extend the length of a lens. Used for "macro" or close-up photography.

 

F

F Numbers
Numbers on the outside of the lens corresponding to the aperture opening. When the number is large (eg. F22), the aperture or opening is small. And when the number is small (eg. F2.8), the aperture is large. The f-number is equal to the focal length divided by the aperture diameter.

Film
Photosensitive material used in a camera to record an image. Made from a thin, transparent base coated with light sensitive chemicals.

Filters
Transparent lens attachments used to change the color, or other characteristics, of an image. They are used both on the camera and in the darkroom.

Fisheye Lens
Super wide-angle lens. Angle of view can approach 180 degrees. Nearly infinite depth- of-field.

Fixed Focal Length
Usually refers to the focal length of a non-zoom lens, the focal length therefore, is fixed and cannot be changed.

Flare
Reflected light from lens elements, metal, etc. Appears as a non-uniform haze or bright spots on the film. Usually occurs when bright light (sun) enters the lens.

Flash
An artificial light source. Can be referred to as electronic flash and is usually camera mounted but there are also larger studio models called strobes.

Flash Sync (Synchronisation)
The shutter speed that corresponds to the timing of the flash. Any faster and the shutter won't be open for the duration of the flash. Any shorter and subject movement might cause blur.

Focal Length
The distance between the back lens element and the focal plane. In 35mm format, lenses with a focal length of approximately 50mm are called standard (prime), lenses 35mm and shorter are called wide-angle, and lenses with a focal length of more than approximately 135mm are called telephoto lenses.

Focal Plane
The area of the camera where the lens focuses on the film. Usually marked on the camera body by a circle with a line through it.

Focal PLane Shutter
A shutter placed just off the surface the focal plane.

Focal Point
The point in an image that is focused upon before taking the photograph, and is in sharp focus. The technical explanation is the point on the optical axis where light rays form a sharp image of a subject.

Focus
To move the lens, or film, in relation to the focal plane in order to record a sharp image on the film.

Focus Mode
Three basic types of focus modes exist for AF cameras: Single servo AF, Continuous AF and Manual AF.

Focus Priority
A camera mode where the shutter cannot be released until the subject is in focus.

Focus Tracking
Also called Predictive Autofocus. Where the camera analyzes a moving subject's speed, and anticipates the position of the subject at the exact moment of exposure, and focuses the lens based on this information.

Focusing Screen
A screen in a camera that the image is projected onto (via the mirror in Single Lens Reflex) and enables the user to maintain a focussed image. These can contain different markings to help this.

Format
Can mean either the size of the camera or the size of the film. For camera sizes there are APS, 35mm, medium and large formats. For film formats there are APS, 35mm, 645, 6x6, 6x7, 6x9, 4x5, 5x7, 8x10, etc.

G

Grade
Refers to contrast rating of black and white enlargement papers. Zero is the lowest contrast and 5 is the maximum contrast.

Grain
Small dots that appear on some high speed films when exposed. This can also refer to “noise” on lowlight images captured using a digital camera.

Guide Number
A number used to describe the output power of a flash. This is usually expressed using an ISO film speed of 100 and a foot or meter distance.

 

H

High Key
A high contrast image consisting mostly of highlights with little shadow detail.

Highlights
The bright to white range of tones in an image.

Hyperfocal Distance
The closest distance at which a lens can be focused while keeping objects at infinity acceptably sharp. In other words, the focus distance with the maximum depth of field. When the lens is focused at this distance, all objects at distances from half of the hyperfocal distance out to infinity will be acceptably sharp.

 

Related Articles;

Beginners Guide

Glossary I to P

Glossary Q to Z