Given the tiny size of the samples (80 x 50 pixels) the percentage of
compression is a bit misleading. The smaller the file, the less effective
any compression can be.
So I would imagine (don't have time to check right now) that the
*full-size* scan file would probably give close to a 7:1 compression
ratio. But it also depends a lot on the image content - very
detailed/textured images don't compress well (in terms of reduction in file
size) at all.
At 03:20 PM 6/02/01 -0800, you wrote:
>And, the compression we are looking at, at 100% is only 2:1 at best. If
>this is the type of "translation" JPEG is causing at that ratio, the 7:1
>is going to be pretty damaging.
>I am going to do some of my own test. I don't have a web page, but I'll
>report on the results, or upload small segments to the group. I suspect a
>7:1 compression is going to look like one (Call it researcher bias) ;-)
>>OK, Ed, I'll bite!
>>I've just tried to do some sort of meaningful comparison of originals
>>versus JPG's at 100% quality, and the results are here - no apologies for a
>>hastily knocked up, ugly, web-page ;( :
>>Note that 1024 x 768 resolution would be useful for viewing these images.
>>(But don't panic, I'm only using tiny bits of a scan, and the total web
>>page is only about 40K - I have set it up so that your browser does the
>>In summary, I think that although the differences CAN be subtle, if using
>>any form of lossy compression, keep your eyes VERY wide open, and your
>>If my methodology is suspect, fire away..
>>Regards, Mark T.