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Cameras offer different levels of image quality which is determined by lens quality and the resolution (number of pixels) delivered by the CCD. Basic cameras have VGA resolution CCDs that record images with 640x480 pixels. Next up are SVGA models that record 800x600 pixels and then the XVGA models that create pictures with over 1024x768 pixels. The latest super megapixel models go way beyond these figures – currently creating images up to 3040x2016. If you're buying the camera to take pictures for use on screen you only need to buy a VGA model, but if you demand photo quality you need at least a megapixel variety and even then the quality is only good to about 5x7inch from a normal inkjet printer.
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.
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.
The resolution of a computer monitor, scanner or printer. The more dots per inch, the higher the image quality - provided, of course, that the image is sharp in the first place.
Digital images are made up of square pixels and when the image is low resolution there are fewer pixels per inch. This creates a rough step-like appearance that is most noticeable on diagonal straight edges. This staircase effect is often described as "jagged".
A digital picture can be enlarged in size by adding new pixels to the existing grid. Some camera and scanner software do this as the picture is processed to give higher resolution results. The fact is, interpolation increases the picture by guessing what pixels are required and uses information from the surrounding pixels to achieve this. Although the overall picture count will rise image quality can actually suffer and definition is often reduced.
Unlike resampling here the image size is changed without modifying the resolution. For example if you resized a 10x8in 72dpi photo to 4x6in the dpi would be increased, whereas if you resample youd keep the same dpi.