Image size for PBS posting

Ken K
Mon, 17 Feb 2003 09:48:48 PST
Douglas Westfall wrote:
> Having taken a class in Photo Shop and digital imaging, the "recommended"
> image size was 640 x 480 pixils or 6.5 x 4.5 inches.  That size takes less
> space and less time for encripting to transmit. Images much larger than this
> cannot be viewed on the computer screen.
> How is this done?  In most of the Photo programs, there is a window for
> "Images."  Clicking on this will give you such items a "Image Size," "Image
> Format," and other image controls.
> Of course, ALL images must be JPEG (jpg) formated.  That is the "universal"
> format recognized by both PC and Macintosh systems.

Hello Doug, Mary Sue, et al.

If I may, I'd like to offer a few additional comments with regard to
the courteous use of digital images.

Even at 640 x 480, which I think is still a little large (depending on
the image composition) the level of JPG compression applied to the
image will make a huge difference in file size. Too much compression
can result in image degradation in the form of 'smearing' of fine
details and areas of abrupt color change. The most efficient images
are the result of careful cropping and the appropriate amount of image
compression for that particular image. Most software will offer a
preview of the finished image, allowing the user to easily decide on
the proper balance between final image size, compression and fidelity.

Contributors should examine the finished file size of their images
before uploading, since pixel size is not a good indicator if file
size. Typically, once an individual has made the transition to
cablemodem or DSL, that person quickly forgets the long download times
that their oversized images will require for the modem user.

One other trap to beware of is that of using an image to convey an
idea that could be easily explained with a sentence or two. I see this
happening more and more with the proliferation of digital cameras and
scanners and high-speed internet connections. The Clivia discussion
group on Yahoo has many offenders in this regard.

GIF images also an internet standard, and work with any browser. They
are preferable for line drawings, copies of documents and other simple
illustrations that do not contain a wide range of color, since it
preserves detail much better than JPG.

East S.F. Bay Area, Ca.
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