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A photograph or work of art which is made up of pixels.
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Term that describes using a computer program to change a digital image is also known as image processing or image enhancing. A simple form of manipulation is to remove scratches and dust or to change the subject's colour.
Part of a software programme or plug-in for a programme that is used to alter the appearance of a digital image. Countless options are available to distort, blur, sharpen or add artistic effects.
A device found in digital cameras and scanners that converts analogue picture information (continuous tone subject) to digital data (digital image).
A measure of the brightness and contrast of a monitor or the midtone brightness of a digital image. Adjusting the Gamma slider within an image-editing program will adjust the midtones while maintaining detail in the highlight and shadow areas. Adjust the monitor gamma to make the image appear more natural to your eye. A setting of around 18 is right for a Mac monitor while a 2.5 setting is more appropriate for a PC.
An image sensor is a type of transducer (an electronic device that converts one type of energy to another). This particular type of transducer converts light (visual images) to electronic signals, in essence capturing images in an electronic form: pixels. Image sensors are used in digital cameras and other imaging equipment and usually consist of an arrangement of charge-coupled devices (CCD).
The number of bits used to represent each pixel in a digital image. This figure suggests the image colour or tone range.
A digital photo that contains enough pixels per inch to suit the media it will be displayed on. If it's only being viewed on a PC monitor 72dpi is fine (although not high resolution) while an image being printed in a magazine has to be 300dpi.
An image editing device used to cover part of a digital image that can then be left untouched while you apply a filter or effect to the rest of the picture.
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A digital image formed by a grid of pixels. The computer assigns a value to each pixel - ranging from 1 bit of information black or white) to as much as 42-bits per pixel.
Where pixels are added to make a digital image look smoother.
Common name for an electronic document or digital image.
Software program that may be used to view, store, catalogue and enhance digital images.
Where pixels are removed (lost) to make the file size of a digital image smaller. When compressing images using the JPEG format you have the option of varying the level of compression. A higher level makes the file size much smaller but removes more pixels.
Where the data of a digital image is changed or optimised without removing pixels. This is necessary when using pictures on the Web that need to be as small as possible. Some programs have an auto optimising feature that will convert the picture to a JPEG and include the necessary colour palette to ensure the picture looks as good as it did before optimisation.
Name used to describe a print or transparency that's produced from a digital image.
A lossless compression file format thats ideal for digital photography.
Extreme wide-angle lens that gives 180 degrees coverage and is uncorrected for curvilinear distortion so you produce a heavily distorted photograph. If the photo turns out to be rectangular or circular, and how distorted it looks, depends on the lens and the camera. There are basically two kinds of fish-eye lenses for photography: 1. Lenses that produce a circular image, typically 8 or 10mm lenses, used on 35mm cameras or full-frame digital cameras. They produce a circular image with dark corners (due to most photos being rectangular). A similar lens is available for digital cameras with a so-called "cropped sensor". To achieve the same circular effect, it's a 4.5mm lens. 2. Lenses that produce a rectangular image. These lenses enlarge the image to cover the whole rectangular frame of a photograph. They are typically 15 or 16mm lenses. On a 35mm or digital full-frame camera they produce rectangular but still heavily distorted images without dark corners. The same lenses on a digital camera with a cropped sensor will still have a distorting effect, but less so. Fish-eye lenses used to be prime lenses only, but one company has gone so far as to produce a 10-17mm fish-eye zoom lens. This lens still produces distorted, curvy images, but zooming in lessens the distortion.
Advanced Photo System type-C should not be confused with the Advanced Photographic System (APS) camera/film system, since the former is digital and the latter is analogue. APS-C is a type of image sensor found in certain digital single lens reflex (DSLR) cameras. These sensors are smaller than the ones used for the conventional 36 mm x 24 mm (35 mm) sensor SLR cameras (also called full frame DSLR cameras). Being smaller causes a 1.x multiplier for the effect of the focal distance of the lenses, in comparison with the effect of those lenses on conventional 35 mm film SLR cameras or full frame digital SLR cameras. Several manufacturers produce cameras with an APS-C sensor and some even make lenses especially for them. These lenses are found in the Canon EF-S, Nikon DX, Pentax DA and Sigma DC ranges, to name the most popular ones. The most common multiplier ratios are 1.6 (Canon), 1.5 (Nikon, Fuji, Sony, etc.), 1.3 (Canon). (1.3 crop sensors are also sometimes called APS-H.) Most manufacturers not only produce cameras with these cropped sensors, but also offer DSLR cameras with full frame sensors.
A digital process that reduces the number of bits in an image to reduce the file size. The benefit is that it takes less storage space and can be e-mailed quicker. There are two types of compression – Lossy which permanently loses detail and Lossless that returns all the data. JPEG lossy compression is the common method for digital imaging and can be adjusted to offer low compression which maintains most of the quality or higher compression which starts to affect image quality.
Used to indicate the light sensitivity of a film. Digital cameras also use the ISO rating to indicate the CCD sensitivity. The standard rating is ISO100 and as this is increased it means that faster shutter speeds can be used. When the ISO is doubled, it doubles the available shutter speed. The drawback for digital cameras is that increasing the ISO increases the amount of digital noise in an image.
This is how the camera adjusts the shutter speed and aperture to ensure the right amount of light reaches the film or CCD. Early cameras only had a manual mode (M) where the user had to select the aperture and shutter speed manually to ensure the correct exposure. Over the years cameras have become more sophisticated and now offer several automated modes including Program (P) - a fully automatic exposure mode that sets the aperture and shutter speed; Aperture priority mode (AP) where the user selects the aperture and the camera sets the necessary shutter speed; and shutter priority (SP, or Tv on some cameras) where the user selects the shutter speed and the camera sets the necessary aperture. Auto bracketing (AB) takes a pre-selected number of photographs, one at the suggested exposure and one to either side, so you can be sure of one accurate result. There are also several subject-based program modes that we haven't listed here that tailor the camera for particular subjects such as sports (action), landscapes, portraits, or flowers (close-ups). Some digital cameras have black & white and sepia modes. Buying advice A full auto program mode is ideal for point-and-shoot photography, but it's also useful to have some control over the exposure. The beauty with digital is that you can see whether the camera has got the shot right by previewing the image on the LCD. If not, you try again. If there is no manual control you can often preset the exposure using an auto-exposure lock or exposure compensation. The subject based program modes are often a waste of time and don't really bring much to the package. Special effects modes on digital cameras are also throw-away because all these can be created using the computer later.
This is the eye of the camera and is used to capture the image it sees onto the camera's light sensitive film, or CCD in digital camera. The size of lens is measured and indicated as a focal length. Cameras come with either a fixed lens or zoom lens with a range of focal lengths (see lens range) and on some SLR and rangefinder cameras the lens detaches so others can be attached to increase versatility. With a detachable lens camera it's often possible to buy just the body with a lens of your choice.The amount of light passing through the lens is controlled by an aperture, which is often quoted with its maximum aperture setting.Buying adviceSLRs: If you intend buying a specific lens in the future make sure that it's available in the same mount as the camera you are considering or own. Also if you're upgrading cameras, buy one with the same lens fitting or one that can be adapted to save the cost of replacing all the lenses you own.Digital and compact cameras: A fixed lens camera can often be much smaller so could be selected if you need to travel light. It's also less expensive if your budget is tight. It's better, though, to choose a camera with a zoom if you can afford to, rather than using a digital zoom or cropping the picture later. Go for one with a wider angle zoom if most of your pictures will be landscapes, interiors or family group shots.Choose a version with a longer telephoto setting if you want to shoot long distance subjects, portraits and wildlife.
A charge-coupled device or image sensor. It consists of an integrated circuit with an array of linked ("coupled") capacitors which are sensitive to light. In digital photography, the CCD is used to capture images, which in analogue photography would be captured on film. CCD technology is not only used in digital photography, but also in astronomy and other branches of science.
The camera's light sensitive CCD converts the scene into a grid of pixels that make up a digital photograph. The resolution is the total number of pixels in the photo, for example, one million or 350,000. This is one factor that affects image quality, providing the image that's being formed on the CCD is sharp. CCDs with greater numbers of pixels should have higher resolution. Buying adviceUnless you have a specific need for a low resolution model choose a camera with the highest resolution you can afford. This will enable you to make bigger enlargements.