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filmscanners: RE: filmscanners: Re: Hello, thanks, and more.

Ken wrote:
>1) Bits.  I need some clarification on what the siginificance
> of all the different bit-rates are about for color.
> The Canon software only offers scanning in 24-bit color

AFAIK the 2710 produces more than 24 bits RGB at the A/D. 42 maybe?  If
you're using something like Vuescan, the idea is to get it to produce a
file with as many bits per channel as your scanner can produce, so you have
the maximum possible data to work with before you reduce it to 24 bits.
 There's no such thing as a 42 bit file because computers work with 8 bit
bytes.  So your 42 bits of data are stored as a 48 bit file (16 bits per

Using an editor with a 48 bit file initially allows you to pick the "best"
24 bits, or the 24 bits you actually want, before losing that data and saving
as a 24 bit file.

Very few editors can work directly with 48 bit files (16 bits per channel).
 Most only work with 24 bits.

>saving,  I go into the properties dialogue and specify a web-based
>size, i.e. about 750 pixels in the longest dimension. Is that
>"downsampling?"  Is that process in itself "lossy?"

The only way you can change the "dimensions" of an image without changing
the number of pixels is to change the dpi.  For example, a 300x300 pixel
image at 300 dpi will print 1" x 1" on paper.  If you change the dpi to
150 dpi, it will print 2" x 2".  No change in the number of pixels!  If
you're resizing an image from 3000 pixels in the width to 750 pixels, you're
throwing away 75% of the data!


Rob Geraghty harper@wordweb.com


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