P3D scanning slides

[Tom Deering <tmd@xxxxxxxxxxx>]

>The adapter is a great value for $5.50, but there still is a reason that
>high quality film scanners (2700DPI, 36-bits, 40 sec. scan time) cost
>well over $1500.  To find out more about high quality scanning of stereo
>slides, visit

I don't know anything about stereo photography, but as a graphic artist who
uses a computer every day, I can tell you a little about scanning slides.
The $1500 scanner mentioned above is overkill, unless you are submitting
your slide for the cover of a magazine.

The poor results some of you have seen are due to: 1) the scans are out of
focus due to the thickness of the slide mount, and 2) the illumination is
not good enough for scanning, and  3) your scanner is illuminating the
front of the slide, even if you are shining light _through_ it.  The DPI is
not a factor.

First, the thickness of the mount means the film does not touch the glass
directly.  Since a scanner is focused very accutely at the surface of the
glass, with no depth of field at all, your results will be blurry, no
matter what DPI you scan at.  You can see this is true by placing a naked
film chip directly on the glass.  Way better results, but who wants to
unmount their slides?

Second, the optical sensors on your scanner are calibrated for a specific
source of illumination.  A light box or flashlight will throw off your
colors wildly.  You can tweak these in Photoshop, but be prepared to be
patient.  Your scanner will only give decent scans of slides if there is a
source of illumination built-in.

Third, if your scanner is not made for transparencies or slides, then the
light is on all the time, illuminating the front of the slide. This alone
will wreck your scan, making them look washed out.  This is hard or
impossible to fix in Photoshop.

You either need a slide scanner, or a flatbed scanner with a slide adapter.
Note that this is not the same as a transparency adapter.  A transparency
adapter will lick problems 2&3  above, but not problem 1.  $400 will buy a
transparency scanner, $700 a slide scanner.

Also, note that scanning at 600 or 1200 will not help at all.  Just the
opposite.  Calculate the correct DPI based on the original size, the
display DPI and the display size.  Scan using this calculated DPI, rather
than resizing in Photoshop.  The resize will kill the clarity of your scan
because of the pixel averaging.

For the occasional web page thing, you can unmount your slide, illuminate
with a bright lightbox, and tweak color in Photoshop for so-so results.

Cheers,

Tom Deering



------------------------------