Sil Horwitz (silh@iag.net)
Mon, 01 Feb 1999 18:45:28 -0500
At 05:24 AM 1999/02/01 -0800, Andy wrote:
>In the thread about scanners, I haven't seen mentioned one I've seen
>advertised the last three weeks in several electronics ads. It's an
>IBM color flat bed scanner with 9600dpi-x-9600dpi res (yes, that's
>what it says) for $150. No knowing much about them beyond resolution,
>what am I missing? What's not being said in the ad?
As many others have warned, do not be misled by interpolated resolution. In
the low-price flatbed scanner field today there are two basic types: the
300x600 dpi optical resolution, which can be interpolated to a really fake
9600 dpi, and the 600x1200 dpi optical, which can reach the 9600 dpi
(though you'll be hard put to have enough memory to capture that
resolution, even for a 4x5!). I just purchased an Acer 600x1200 dpi for
$110, which claims (in writing) to have an "electronic" 19200 dpi
resolution. At that top "resolution" a 4x5 scan would work out to a
bitmapped 7.3 gigabytes! (7372 megabytes).
While on this scanner subject, there have been a lot of conjectures
concerning using a scanner with a camera. Won't work with flatbed scanners
- they work by reflection, with the ccd elements moving horizontally and
vertically along with the light source. If the light source were
disconnected, a camera would have to act by scanning in the same way.
Doesn't sound practical to me.
Also, with regard to using flatbed scanners for negatives and slides, it's
not very practical, as the true resolution isn't good enough. Slide and neg
scanners have true optical resolutions of 2400 dpi and up. As to making
your own transparency attachment for a flatbed scanner, the lamp lighting
the transparency must be synchronized with the movement of the ccd sensor.
Could be done, I guess.
Sil Horwitz, FPSA
Technical Editor, PSA Journal
silh@iag.net
Visit http://www.psa-photo.org/
Personal page: http://www.iag.net/~silh/
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