[EMAIL PROTECTED] (2002-04-12 at 0549.14 +0000):
>  Can anyone explain to me what optical resolution means. I 
> am looking at the product specification of an Epson scanner 
> and it says that the optical resolution is 1600x3200 dpi. 
> What does this mean ?

It means the scanner can "see" that many real dots, it can sample that
info from the documents directly. In digital cameras the concept is
similar, the good thing is optical zoom, not digital zoom, cos it
performs the operation directly, not as post process or similar

Internally the hardware have some elements, not necessarily matching
the pixels you will get, but arranged and designed in such a way that
the maximum optimum number of pixels is what "optical resolution"

> The software that comes with the scanner I have gives me a 
> choice to scan upto 9600 dpi. How do I know whether this 
> value is the optical resolution or the software 
> interpolated resolution ?

If it is above optical specs, it is interpolated. I can think a case
in which app wants to give mid resolution at high speed, and scans at
low resolution and then fakes... which is a nasty trick. This trick
should not happen when using maximum quality settings with less or
equal resolution than declared "optical".

In some scanners interpolated is (a bit) better than scaling the image
afterwards, cos the driver has access to the full range of info (some
scan in 30 bits vs 24 of images, for example) as well as knowing how
it is made the hardware and thus can guess better. But you should
always pay attention to optical, it is the real limit, other things
are tricks.

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