| 24-bit image |
This type of digital image has pixels that are allocated 24 bits of storage (usually with eight bits for red, eight for blue, and eight for green), allowinga representation of 256 by 256 by 256 (or more than 16 million) different colour combinations. |
| 8-bit image |
This is a digital image composed of as many as 256 possible colours or shades of grey. |
| AF sensor |
The sensor used to detect and help correct the focus in cameras that are equipped with an autofocus feature. |
| Angle of view |
The width of the area a lens can see which is measured in degrees. |
| Aperture |
The opening behind a camera lens through which light passes to make a photographic exposure. The range of sizes to which the aperture can be set is described by the f-stop numbers (for example, f/1.8 through f/22). Lower numbers indicate larger aperture sizes; the larger the aperture, the more light enters the camera. |
| Aspect Ratio |
This is the ratio of height to width of an image or LCD screen. Images will become distorted if they are forced into a different aspect ratio during enlargement, reduction or transfers resulting in a loss of quality. |
| Autofocus |
A camera feature that uses an infrared beam or sonar to set its focus correctly under a number of lighting conditions. |
| AVI |
Short for Audio Video Interleave. This is the file format for Microsoft's Video for Windows standard, one of several video technologies used on computers. An AVI file is essentially a video clip. Most digital cameras will now record short video clips that can be transferred to a computer and uploaded to YouTube for example. |
| Backlighting |
Illumination of the subject of a photo from behind using artificial or natural light. |
| Bit |
Short for binary digit, which is a computer value of zero or one, on or off; this is the most basic language used by computers but it's not something you really need to be concerned with when buying a digital camera. |
| Bit depth |
This is the colour or grayscale of an individual pixel. A pixel with 8 bits per colour produces a 24-bit image; 8 bits multiplied by three colours which are red, green, and blue - and this equals 24 bits. CCDs are coloured in a pixel-by-pixel way using the following guidelines:
- 32-bit colour (true colour) contains billions of colours; suitable only for high-end professional/commercial use
- 24-bit colour (true colour) contains 16.7 million colours
- 16-bit colour (high colour) has 32,000 colours; the accepted standard for Apple Macintosh
- 8-bit colour has 256 colours; this is the basic setting for Windows
- 8-bit grayscale has 256 shades of grey
- 4-bit is 64 colours or greys
- 2-bit is only black and white
|
| Bitmap |
A way of describing and displaying a graphic image onscreen, pixel by pixel. |
| Byte |
Short for binary term if you must know! This is a unit of storage capable of holding a single character; on almost all modern computers, a byte is equal to eight bits. |
| Card |
Memory chip/card that can be used to store images and data on. Various forms exist, the most popular is Secure Digital (SD) Card. Other formats include CompactFlash, Memory Stick and XD-Picture Cards. The cost of SD cards continues to fall as technology advances. These days you can pick up an 8 Gb SD Card for under $30. |
| CCD |
Short for charged coupled device; which is essentially a mechanism that converts light into a proportional electrical current; the two main types of CCD are linear arrays, used in flatbed scanners and digital copiers for example, and area arrays, which are found in camcorders and digital cameras. |
| Colour balance |
Compensating for too much of one colour in a photo by adding that colour's opposite. For example if a photo has too much blue then adding a larger percentage of yellow would help achieve the right balance. |
| Compression |
This is the reduction of data to reduce the size of a file. Many photo editing packages will suggest compressing images before uploading to the web to reduce the fize size. |
| Contrast |
The rate of change of brightness in an image. A high contrast suggests content consisting of dark blacks and bright whites; medium contrast suggests a good spread from black to white whereas low contrast is a small spread of values from black to white. |
| Depth of field |
This is a way of describing the area of a photograph that is in focus. |
| DPI |
Short for Dots Per Inch which is a measurement based on the dot density of either a printer's resolution or a video monitor image. Most laser printers have a resolution of 300 dpi. Web images are often only 72 dpi. |
| Exposure |
The amount of light that reaches the film due to the combination of f-stop and shutter speed which controls the amount of light that passes through the lens to the film. |
| File format |
A format for encoding visual information in a file. Some common image file formats include JPEG, TIFF, PICT, and EPS files. |
| Filter |
This is a tinted-glass or plastic lens that fits onto the camera lens in order to alter the visual field. |
| Fish-eye lens |
This is a wide-angle lens. A fish-eye lens magnifies the parts of the image near the centre of the image and reduces the parts that are far away from the centre. |
| Flash card |
A memory card that works with the flash memory. This allows the camera to retain your data after the system has been switched off. |
| Flash memory |
A memory chip that has the ability to retain image data even after the camera has been shut off. So, even if the digital camera's battery dies, the image data will remain stored in the camera's memory. |
| Focal length |
The distance from the surface of the lens to the focal point or centre point at which light rays converge. Basically the focal length determines the length of the lens. |
| Focus |
To move the lens or image sensor in order to record a sharp image. |
| GIF |
Short for graphic image format which is an image file format widely used on the Web providing high-quality image compression. |
| Grayscale |
Describe an image that ontains shades of gray, as well as black and white. |
| Halftone |
An image that is reproduced through a series of dots to simulate shades of gray in a photograph. Halftone has been traditionally used by newspapers and magazines for the production of images. |
| Hue |
This is the tint of a colour as measured by the wavelength of light. |
| Image editor |
A graphics program, such as Adobe Photoshop, that provides a whole host of special features for modifying bit-mapped images for photographs and images. |
| Image Stabilisation |
Helps to steady the image projected into the digital camera to compensate for those of us with shaky hands! |
| IR |
This is short for infrared. |
| ISO |
This is a a rating that determines the light sensitivity of the film. ISO (International Standards Organization) provide a standard measure by which all photographic film speeds are determined. All digital cameras rate their CCD's sensitivity as equal to that of a given ISO standard. |
| JPEG |
Joint Photographic Experts Group = JPEG. This is a highly compressed image fil, which takes an area measuring 8 by 8 pixels and compresses this information to the lowest common value. JPEG images tend to be slightly lower in quality compared to other image formats but their minimal size makes it possible to store more images, especially useful if you have limited storage space. |
| LCD |
LCD = liquid crystal display. This is a small, flat screen that employs liquid crystal technology in order to display images. |
| Leaf Shutter |
The leaf shutter is located in the lens. This camera shutter utilises a spring with the aperture control device to control the exposure time. |
| LED |
LED = light emitting diode which is an electronic device that lights up when electricity passes through it. Since they can be seen in the dark, LEDs are usually red and used for camera viewfinder displays. |
| Lens |
A lens is an optical device that focuses light rays. In digital cameras the lens is the device on the front face, or in the tube you will see extending from the front face on certain models, that collects the incoming light and concentrates it so that it can be directed towards the imaging device in a digital camera. |
| Lossless compression |
This is a compression format that minimises the size of files by creating an internal shorthand code which restores the image to its original state before compression. |
| Lossy compression |
This is a compression method that minimises file size by eliminating unnecessary data which often causes a slight degradation of image quality. |
| LPI |
LPI = lines per inch, which refers to the frequency of horizontal and vertical lines on a halftone screen. |
| Luminence |
Luminence refers to the black and white information, including brightness, sharpness and contrast, encoded in a graphic image. |
| Macro |
Macro is the ability of a lens to focus at very close range i.e. when taking close-ups of flowers for example. |
| Map |
Mapping, or to map, is the process of making one image conform to the size, shape or texture of another. |
| Mask |
This is a defined area used to limit the effect of the image editing operations to certain areas of an image. Masks can be drawn manually with a mouse or they can be created automatically using photo editing software. |
| Megapixel |
A megapixel is a measurement of 1,048,576 pixels (approximately 1 million pixels if you will). The more megapixels, the better the potential image quality will be. |
| Memory Stick |
Sony based storage media used mainly in Sony's digital cameras. |
| Negative |
This is a section of a processed film where the image is reversed so that the shadows are light and the highlights are dark. |
| Normal Lens |
This is a lens that accommodates an image of approximately the same angle of view that the human eye is capable of. |
| Opacity |
Opacity is the amount of transparency when combining a fill colour, painted colour, floating selection, pattern or layer with another layer or background. |
| Palette |
A computer graphics term that describes the collection of colours and shades available to a graphics program. |
| Pan |
Pan is a camera technique in which the point of view is adjusted by moving the camera direction along the horizontal plane i.e. following an object such as panning from right to left. |
| PICT |
This is a Macintosh file format used for graphics. |
| Pixel |
Pixel is short for picture element. Aa pixel is a single point in a graphic image. The higher number of pixels, the better the image quality. |
| Pixelisation |
The graininess in an image that results when the pixels are too big to the size of the image. Often when a picture is said to be too grainy it is the result of pixelisation. |
| Polarisation |
This is the use of specific filters to control the direction that light travels. Effects of polarisation include the reduction of glare and reflections, plus the saturation of colours particularly prevalent in landscapes. |
| Posterisation |
Posterisation is an effect produced when a photographic image is displayed or printed with a small number of colours or shades of grey. |
| PPI |
Pixels per inch. This is the measurement of resolution for display or print elements. |
| Primary Colours |
No, not the movie starring John Travolta! Three colours (red, yellow and blue) which when combined at various proportions can produce every other colour! |
| Quadtone |
A printed image created with four different colours of ink, hence quad! |
| Redeye |
The red 'devil' like eyes you often see in photographs are the result of redeye. This is caused by light reflecting off the interior surface of the eye which produces a red glare within the eye. Many photo editing packages can now correct this problem reasonably well. Picasa is one such program. The Retouch tool allows removal of unsightly blemishes and improves photo quality. |
| Reflectance |
This is also known as reflectivity. Reflectance is the fraction of the light incident on a surface that is reflected. |
| Relative Aperture |
Known also as the f-stop. This is the diameter of the aperture of a camera divided by the focal length of the lens. |
| Resolution |
The main thing you need to know is that the higher the resolution, the finer the detail that can be achieved which in turn means better quality images. |
| RGB |
Short for red, green, blue. This is the colour model used for generating video on a display screen as varying intensities of red, green and blue dots. |
| Saturation |
This is also known as colour purity or the amount of colour density. Basically this is the degree to which a colour is diluted by luminance or white light. You can increase the saturation levels to give your photos are burst of colour (assuming the original is not in black and white of course!) |
| Scale |
Scale is enlarge or reduce an image by increasing or decreasing the number of scanned pixels. |
| Sharpen |
Many graphic programs enable you to enhance the contrast on the edges of light and dark shapes to make images appear more in focus or sharper. |
| Shutter |
Not the 2008 horror flick about a newly married couple how discover disturbing, ghostly images in photographs they develop after a tragic accident! No, in this instance the shutter is a camera mechanism that opens and closes at specified intervals in order to allow light to pass through the lens. |
| SVGA |
SVGA - This is short for Super Video Graphics Array, originally defined by IBM. This represents a computer graphics adapter capable of 800 by 600 resolution. |
| Thumbnail |
Not the nail of the thumb, but a small representation of an image used as an aid previewing graphics and images. |
| TIFF |
TIFF is short for Tagged Image File Format which is a computer graphics file format developed by Aldus, Adobe and Apple! |
| UCR |
UCR is s hort for undercolour removal which reduces the cyan, magenta and yellow inks from the darkest shadow areas in an image by replacing them with black ink. |
| Viewfinder |
An optical or in the case of digital cameras, an electronic display used to frame an image in the camera. One can look through the viewfinder in order to see the image that will be captured by the camera. A preview screen if you like. |
| Watermark |
These are bits altered within an image to create a pattern, stamp or marker of some sort that indicates proof of ownership. Unauthorised use of a watermarked image, even an invisible watermark, can be traced. Getty images are one such company who have used this technique to find their unauthorised stock library images being used on the web. |
| White Balance |
This is the balancing of colour components to create pure white colour when scanning a white object. |
| Wide-angle Lens |
This is a lens that has an angle of view greater than that of a standard lens. This kind of lens is used to include more of a subject or scene within the confines of the image. For example, to capture a landscape scene one would use a wide angle lens. |
| Zoom |
Digital camera advertisements will boast about having both optical and digital zoom. These are very different and the numbers can be misleading, so it’s important to know which zoom will actually give you quality results.
Optical zoom lenses actually "move" one closer to the subject of the photograph without sacrificing on the quality. The higher the optical zoom rating on a camera, the farther away you can be to take a photograph and still get a really clear, close-up qualityimage. The concept of optical zoom essentially the same as the zoom on a movie camera. Optical zoom is the number you want to pay close attention to, not the digital zoom.
Digital zoom is not bringing you closer to the item at all. No, in this case the camera crops the entire image, and then digitally enlarges to the size of the viewfinder the portion you want to zoom in on. This results in a loss of quality and is no different than cropping and enlarging an image with editing software such Photoshop. The benefit of using image editing software instead of the digital zoom on a camera is that you can decide how much to crop. But of you use digital zoom on the camera the image quality is lost.
In short, forget about the digital zoom when comparing the specificaitons of cameras. It is the optical zoom should be interesed in. The higher the better! |
