Understanding Resolution
Resolution is the term that refers to the number of pixels in an
image. Sometimes it's referred to as DPI (dots per inch). Higher
resolution means that more dots are used to define the image - that
means
higher quality and a larger file size. Most everyone has
seen that a newspaper photograph is made of dots. Magazine photos
are too. But you can see the dots better in a newspaper than a
magazine, because the magazine has more dots per inch (dpi) than the
newspaper, resulting in a finer, better detailed image. 72 dpi is
sufficient for email, web or on-screen viewing. If you wish to print
high quality images, you
should use 200 or 300 dpi. Most scanners
are capable of scanning 600-1200 dpi. Digital cameras are sometimes
a bit confusing. They often save images at 72 dpi, though the images
are very large. A 3-Megapixel camera can save images that are
20"x30" at 72dpi. Below are some example images that demonstrate
the effects of resolution.
The image at the left is much sharper than the image in the
center or the image on the right. That's because the image on the
left has more dots in any one inch. The dots are smaller and shaper,
resulting
in a better image. (Note: The smaller images have been
enlarged so all three appear at the same width and height.)
The resolution also affects the size of the file. More dots and
higher quality means there is a greater amount of data. Saved as
medium quality JPGs, the file on the left is approximately 29 K, the
one in the center is 20K, and the one on the right is 18K.
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