From: Ken Watson (watsok@frii.com)
Date: 12/01/02-12:30:41 PM Z
Sandy,
This really would depend on many things. The one issue I am most familiar
with has to do with the sensor.
If the sensor had a separate set of color photodiodes for 300 DPI
resolution ( or even 600 DPI ) the 300DPI would be best because there would
be a higher signal to noise ratio.
In many cases, a 2400 DPI sensor that is run at 300 DPI has 3/4 of the
information thrown away for a faster scan. ( every 4th or 8th pixel is
used).
It could be that the software is accumulating the charges from 8 sequential
pixels and sums them for 300 DPI resolution. This is still not as good as a
straight 300DPI sensor because the signal to noise ratio is still the same
as the 2400 DPI sensor. But it has a better chance of getting that
particular pixel the correct density / color.
Perhaps there is information about how the software handles different
resolutions in the manual. A way to see for yourself is do a scan at
2400DPI resolution and another at 300. If the 300 DPI scan is faster (
takes less time )there is a good chance that there is a lot of info being
dumped. Try to determine if Epson specifically states they have an
additional set of color stripes / sensors for doing lower image resolutions,
which I strongly suspect is not the case. If they do have additional sets
of sensors then the above speed test is invalid.
----- Original Message -----
From: "Sandy King" <sanking@clemson.edu>
To: <alt-photo-process-l@skyway.usask.ca>
Sent: Sunday, December 01, 2002 10:57 AM
Subject: Warning: Digital Question
> I have a scanning resolution question.
>
> Situation is this. I am scanning a 4 X 6.5" section of a 5X7" color
> negative with the Epson 2450 flatbed scanner, which has optical
> resolution of 2400 dpi, using SilverFast scanning software as a
> plug-in to PhotoShop. The eventual purpose of the scans is to make
> color prints approximately 13X19" in size, or to make negatives for
> alternative printing. I understand that a maximum resolution of a
> little over 300 dpi at the printing size is needed for either purpose.
>
> My question is this. What are the pros and cons of of the two
> following scenarios: 1) scanning at 100% of the 4 X 6.5" negative
> size at the maximum optical resolution of 2450 dpi, re-sizing later
> in PhotoShop, or 2) scanning at the desired printing size of 13X19"
> 300dpi?
>
> Sandy King
>
>
>
>
>
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