Graphics Programs Reference
In-Depth Information
Scanners work in a similar
way, except that these de-
vices use rows of CCD sen-
sors that move slowly over
the original, sampling the
picture as they go. Gener-
ally, different scanners are
needed for converting film
and print originals; how-
ever, some companies are
now making products that
can be used for both.
Video cameras use the
same principle but rapidly
capture a sequence of im-
ages. Any movement in
the subject is recorded on
successive photos. When
these images, or frames,
are quickly redisplayed one after another, the motion of the subject is replicated on screen.
Until recently, capturing digital video required a separate camera, now, many still cameras
also contain a very usable video mode.
A digital picture is made
up of a grid of picture
elements or pixels.
Photographs and negatives, or slides, are converted to digital
pictures using either film or flatbed scanners.
The quality of the digital file is largely determined by two factors - the number of pixels and
the number and accuracy of the colors that make up the image. The number of pixels in a
picture is represented in two ways - the dimensions, i.e. 'the image is 900 × 1200 pixels', or
the total pixels contained in the image, i.e. 'it is a 3.4 megapixel picture'.
Generally, a file with a large number of pixels will produce a better quality image overall
and provide the basis for making larger prints than a picture that contains few pixels. The
second quality consideration is the total number of colors that can be recorded in the file.
This value is usually referred to as the 'color or bit depth' of the image.
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