FOR SCREEN PRODUCTS
Resolution issues for image use in webpages or multimedia production are much more straightforward than for print, since the designer knows that the audience will be viewing images on a monitor not dissimilar to the one on which the design was created – so the size you see is the size you’ll get. At 96ppi, roughly the resolution of the average modern PC monitor, images contain just 9,216 pixels per square inch, about a tenth the size of a 300ppi file. Apart from bringing file size (with compression) down within a practical range for the Internet transmission, this also means the designer’s software will work faster than when editing high-resolution print files.
Vector images allow for good-quality scaling both on screen and when output from a printer’s RIP (see page 66). When a vector image is re-sized, the mathematically formulae ensure that all the points and paths are repositioned so as to maintain their original relationships. Since colouring is simply the filling-in of a defined shape, the scalledshaped is automatically refilled. Objects described by outline information are memory-efficient, since a relatively compact set of numbers can describe quite complex shapes and color fills. Vectors, however, cannot produce photo-realistic images, since realism needs a constantly shifting description of tone and colour that can be satisfactorily carried out only by the subtle changes in pixel colour achievable by bitmap techiniques.