Aberration - Deficiencies within a lens or optical system cause imperfections in an image and these can be aberrations of shape, sharpness and colour.
Ambient Light - The Natural light in a scene
Aperture - The circular opening inside the camera's lens. The diameter of this can be changed to control the amount of light reaching the camera's sensor.
Application - A computer program such as an imaging package (photoshop/elements/lightroom) or a web browser such as Internet Explorer/Safari/Flock.
Archival Quality - Materials such as paper/cd/dvd/etc have a time period of acceptable performance and a time period before they start to degrade. If the material exceeds an acceptable defined time period before starting to degrade, it is said to be of archival quality.
Artifact - An unwanted visual aberration within a digital image, often caused by over-compression
Aspect Ratio - The proportions (or ratio) of a picture's width to its height
Backing-up - Making copies of important computer files and applications/programs in case the originals are damaged and cannot be accessed
Buffer - Before the photos are written to the memory cards they are stored by a memory reservoir built into digital cameras.
Burning (image editing) - Selectively darkening part of a photo with an image editing program such as photoshop
Cast - The effect of one (unwanted) colour dominating the look of an image. Often caused by exposure errors or incorrect settings of a digital camera's white balance for the ambient/artificial lighting.
CCD - Charge coupled device. One of the two main typed of image sensors (see also CMOS) used in digital cameras. When you take a picture, the CCD is struck by light coming through the lens and the millions of tiny pixels that make up the CCD convert the light to electrons. The number of electrons is measured and converted to a digital value, a step that occurs outside the ccd, in the camera's analogue-to-digital converter.
CMOS - Complementary metal-oxide semiconductor. One of the two main types of image sensors used in digital cameras. Its basic function is the same as that of the CCD.
CMYK - Cyan, Magenta, Yellow, Black. The four colours of many photo quality printers. Some more expensive photo-printers use six, seven or even eight inks to achieve smoother, more photographic prints.
Compression - Helps to maximise storage space by removing redundant and/or non-critical information within a digital image and thus reducing the file size of digital data files
Contrast - The difference between the darkest and lightest areas in a photograph. The greater the difference, the higher the contrast.
Copyright - Legal protection against copying and the specific rights allowing the copying applying to original works such as photographs.
Depth of Field (DOF) - The distance between the nearest and farthest points that appear sharp focus in a photo. DOF varies with lens aperture, focal length and camera-to-subject distance.
Dodging - Selectively lightening part of a photo, using image editing software such as photoshop.
DPI - Dots per inch. Measurement of the resolution of a digital photo print or digital device such as an inkjet printer. The higher the DPI number the greater the resolution.
EXIF - Exchangeable image file. Image data (such as shutter speed, aperture and ISO) that's stored directly in the image file generated by a digital camera. The data can be read by any application that supports JPEG and TIFF file formats.
Exposure - Exposure is measured in EV and the higher the EV, the more light there is, exposure is the amount of light allowed to hit the camera's sensor.
Fill Flash - A flash technique used to brighten deep shadow areas, for example, outdoors on sunny days.
F-stop (or F-number) - The measure of the size of a camera lens' aperture. The higher the F-stop, the smaller the aperture and vice versa.
Greyscale - An image made of varying tones of black and white.
Highlights - The brightest parts of a photo
Histogram - A graphic representation of the range of tones from dark to light in a photo.
Image Resolution - The total number of pixels used to make up a digital photo.
ISO Sensitivity - This it the camera sensor's sensitivity to light. The higher the ISO number (100, 200, 400 etc) the more sensitive to the light the camera becomes, but as ISO speed climbs, image quality drops. (see noise).
LCD - Liquid crystal display
Noise - Unwanted random artifacts within an image created by the electronics within a camera and other environmental factors such as heat. Often used together with the term signal-to-noise ratio, which describes the actual image information (the signal) and the level of background noise. A high signal-to-noise ration is desirable.
Panning - Photo technique in which the camera follows a moving subject, keeping the subject sharp whilst blurring the background giving a sense of movement in the photo. Used a lot in sports/action photography.
Pixel - A picture element and building blocks of a digital photo. Millions of pixels make up a digital photograph.
Pixelated - Poor quality images where the balance between image resolution and output is not correct when printing. For example, is a low resolution image (say 72dpi) is enlarged by 200% and printed, the pixels become visible - hence pixelated - giving a jagged effect to the printed image.
PPI - Pixels per inch. Measurement of the resolution of a digital image is made in PPI. The greater the ppi the greater the resolution.
Redeye - the reflected red glow from a subjects eyes when light from flash is coloured by the blood vessels in the retina.
Resolution - The ability of a lens or optical system to show fine detail. The higher the resolving power of a lens the more detail can be captured.
RGB - Red, green, blue. The three primary colours into which digital cameras split/convert an image.
Saturation - Measure of how richly colours are rendered in a photo.
Sensitivity - see ISO
Sensor - see CCS AND CMOS
Sharpness - The perceived clarity of detail within a photo. Can usually be adjusted in the camera or later with image editing software.
Shutter Speed - Measure of how long the shutter stays open as the photo is taken.
White balance - A function on the camera that allows for compensation for the different colours of light being emitted by different light sources.
I will add more as i come across them