Re: Photographing irises
- To: i*@rt66.com
- Subject: Re: Photographing irises
- From: i*@easynet.co.uk (Ian Black)
- Date: Mon, 30 Sep 1996 22:07:28 +0100 (BST)
Just a quick word about scanning photos. If you plan to scan slides, the
"slide attachments" available for flat-bed scanners usually only allow you
to scan at the basic resolution of the machine itself - usually between 300
and 600 dpi. The improbably high resolutions of many cheap scanners are due
to interpolation - (i.e. "smearing" the data between the dots at basic
resolution) and contribute little other than to fill up the hard disk quicker.
If scanning slides is what you want to do, a better bet would be to use a
film scanner. There are a number of these, and the low-end models usually
work at a true resolution of 2500 to 3000 dpi. I believe that this is not
far off the optical resolution of a 200 ASA film. Another big plus point is
that they can also scan negatives and perform the reversal process on these
to give you your files in colours the right way round (!) - thereby missing
out on the idiosyncracies of the printing process.
However, be warned - a full resolution scan of a 35mm slide/neg occupies
29MB. You don't have to use the full resolution, but it is essential if you
need to enlarge or crop the original.
There has been a lot of wise advice on this subject. It's interesting to
watch the capability of digital imaging improve yearly. However, even the
professional digital cameras, costing a year's pay, still do not approach
the resolution of a reasonable secondhand SLR, which is many times cheaper.
Ian
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Ian Black ianblack@easynet.co.uk
Hampshire, UK - mintemp -8C
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