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[filmscanners] Re: PNG File format?

"Mark Otway" <mark@otway.com> asked:
"Just looking at file formats for archiving images. I've been told that
PNG is a lossless format that supports 24-bit (or higher) colour, and
has a compression ratio similar to Jpeg? Is this true? Is there any
sensible reason why I shouldn't archive my scans in this format rather
than JPEG? (I don't archive raw scans as they simply take up too much
space - I've got over 3,000 images to store)."

You might check out http://www.photodex.com/png/pngintro.html (uncovered
in a Googlesearch for "PNG".) It sounds like PNG is a replacement for
GIF to get around some possible patent issues.

I would not hesitate to use JPEG images for archive if I couldn't afford
the file-size-cost of TIFF images. At a previous job in a printing
company, we did lots of testing on high-quality furniture images
compressed by JPEG, and we found the medium-level-compression images
were indistinguishable from uncompressed images as long as the images
had sufficient resolution.

I save most images as approx. 1800x1200 pixel JPEG's compressed at level
6 in Photoshop, giving me approx. 0.3Meg files instead of 6Meg TIFF's.
These are suitable for reproduction at up to about 5"x8". If I think I
might want to use the image larger or crop the image significantly, I
save 3600x2400 pixel images which are about 1.2Megs.

Preston Earle

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