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Re: filmscanners: JPEGs, TIFF's and suchlike



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) ;-)
>
>Art
>
>markthom@camtech.net.au wrote:
>
>>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 ;( :
>>http://www.adelaide.net.au/markthom/compare.htm
>>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
>>magnification..)
>>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
>>magnifier ready!
>>
>>If my methodology is suspect, fire away..
>>Regards, Mark T.
>




 




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