"William M. Miller" <std.com> wrote in message
The size of a digital image is X by Y pixels. The unit for file size is
bytes, usuall expressed as Kb or Mb.
Compression doesn't change the number of pixels, but it can cause other
image defects. The greater the compression, the more chance that these
defects will show up, but the less the ocmpression the bigger the file
size - and the smaller the number of files that will fit in a memory card.
A good test is to look at an area of slightly changing colors, like a
cloudless sky. With too much compression you'lll see banding.
This refers to resizing the image - changing the number of pixels in the
width and height. A good image editor should let you choose the compression
algorithm; if you don't like the result, undo it and try another algorithm.
I use Paint Shop Pro. If it is done in the camera, you don't have that
control. I always take photos at the largest number of pictures that my
camera allows, unless I'm on a long trip and am running out of memory cards.
Take a series of test shots with different image sizes and compresssions.
Compare them critically. Then decide what you want to use most of the time.
For the occasional critical picture, you can reset the camera for maximum
number of pixels and minimum compression, or even use an uncompressed
format, such as TIFF.
Always save the files directly from the camera, without any change. Storage
on a CD is the most cost-effective. Blank CDs cost a few cents on sale, and
can store hundreds of image files, and if your computer only has a CD-R
drive, you can replace it with a CD-R/W drive at low cost. When you edit a
picture and have to save it, do not overwrite the original file, but save
the altered file with a new name or in a different folder. That way, you
can always go back to the original file.