From: Garth Wood <garth@xxxxxxxxxxxxxxx>
At 01:06 PM 10/6/99 -0500, Garry Lewis wrote:
>>>I have a Polaroid Propalette 8000 at home that can output
>slides up to 8000 lines resolution. <<
> ^^^^^^^^^^^^^^^^^^
>
>I find that amazing since most lense have only a max. resolution of 100 lpm
>and the highest film I've seen was 200 lpm resolution.
>
>May I call for a bit of clarifaction on the words lines resolution?
As for the scanners, I suspect the one I own (the Polaroid SprintScan 4000)
is already pushing the practical limits of most films -- in many instances,
I can already resolve *grain* in the film, leading me to believe that 4000
lpi (approx. 158 lpmm) is about as much as you could ever usefully use.
Just a reminder -- it takes a minimum of two pixels to resolve a
line, so a 4000 spi (samples per inch) scanner is theoretically
capable of only 78 lpmm. (4000 / 2 / 25.4).
In reality, it is not even that good. Inexpensive CCD sensors in
common use bleed charge between cells, and are NOT capable of
resolving adjacent black and white pixels. If you scan a sharp,
high-contrast transition and view it at 4000r so, you'll see that
the transition forms a gradient over several pixels that is not
visible in the original with a loupe.
: Jan Steinman <mailto:Jan@xxxxxxxxxxxxxx>
: Bytesmiths <http://www.bytesmiths.com>
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