From: ken watson (watsok@frii.com)
Date: 03/07/01-11:07:46 AM Z
HP sells a small device that in effect takes light from the additional area
of the flatbed where the slide is not and illuminates / backlights the slide
with this light.
You can do this yourself by having two mirrors joined at about 90 degrees.
Half over the open area , half over the slide.
There may be artifacts from this but putting a diffuser behind the slide may
fix them.
When you place a mirror behind the slide the light must travel through the
slide twice before being detected.
The problem / good thing about slides is their dynamic range. The problem
comes in the scanner sensor which can be over driven to the point artifacts
show up from the scan. If scanned at to low light level you loose
information that is in the slide. If you are just scanning to get a
recognizable image try the slide adapter. Check out HP's site for help.
Using another light source other than the one in the scanner creates
problems of color balance. Just before scanning the light is turned on and a
reading is taken of a known white area. This is used to calibrate the
sensor. In addition you will notice that the light in the scanner looks to
be blue. This is because the scanner's sensor is less sensitive in the blue
region. A common light usually does not contain this much blue so using it
as a backlight will "warm" up the image.
Since you have an all in one you may have other issues in that model may use
a L.E.D light vs florescent source AND the depth of field may be such that
the slide will need to be taken out of it's mount , if in one, to be in
focus. Also the available light level may be "challenged".
..-----Original Message-----
..From: Ed Herny [mailto:edphemra@pacbell.net]
..Sent: Wednesday, March 07, 2001 1:14 AM
..To: alt-photo-process-l@skyway.usask.ca
..Subject: Scanning Autochromes
..
..
..Hello,
..I am presently researching an old autochrome of Yosemite National Park
..as to possible photographer and date. My first challenge is to
..successfully scan the image. My scanner is not designed for
..transparencies, so I'm having to improvise (experiment). My scanner is
..a Hewlett Packard OfficeJetPro 1150C (combination flatbed scanner,
..copier, printer).
..I have tried placing a mirror face down on top of the autochrome to try
..and reflect light back through it, but this did not work. I have also
..tried placing a small "light box" with a typical translucent white
..plexiglas surface face down on the autochrome to shine light through
..it. This produced an image, but it added wide horizontal streaks
..parallel to the scanning pattern, and the color was badly distorted.
..Has anybody had any experience in trying to get a standard scanner to
..scan transparencies by using an outside light source (or any other
..method)?
..Any help would be appreciated.
..Thanks.
..Ed Herny
..
This archive was generated by hypermail 2b30 : 04/02/01-09:55:25 AM Z CST