-------- Original Message --------
Subject: Re: idea about image acquisition
Date: Mon, 19 Sep 2011 11:45:25 -0400
From: David Thulman <[email protected]>
To: [email protected]
I have had problems with shadows also. I have used a simple white sheet
of paper as the background and then manipulated the image in Photoshop
to try to eliminate the shadows, with variable success. I recently made
a black background from a shoebox spray painted on the inside with black
matte paint. In preliminary tests, all background light is absorbed and
the image has a crisp edge. The real test will be when I try to scan
dark artifacts. Another option would be to use light absorbing paper
that is typically used to line telescopes. I've not tried it, but it is
supposed to be great at eliminating light scatter. I would like make
another light box with matte white paint that is effective at scattering
light well enough to prevent shadows, but I'm not sure that's possible.
Dave Thulman
[email protected] <mailto:[email protected]>
On Mon, Sep 19, 2011 at 11:10 AM, morphmet
<[email protected]
<mailto:[email protected]>> wrote:
-------- Original Message --------
Subject: RE: idea about image acquisition
Date: Fri, 16 Sep 2011 22:33:52 -0400
From: Sarah Degroot <[email protected]
<mailto:[email protected]>>
To: [email protected] <mailto:[email protected]>
<[email protected] <mailto:[email protected]>>
I use a flat bed scanner to capture images of leaves. In general it
works well; however I have had some trouble with artifacts from
shadows, particularly for small, lobed leaves when scanned on a
white background. If I scan against a black background the shadows
don't show, but (depending on the species) sometimes hairs on the
leaves show and add a different artifact. So far my simplest
solution is to scan each leaf twice, once with a white background
(so the hairs don't show) and once with a black background (so the
shadows don't show). However, when small, hairy leaves produce
shadows, neither background works very well. I'd love to hear ideas
about how to get around this.
Thanks,
Sarah De Groot
sarah.degroot[AT]cgu.edu <http://cgu.edu/>
__________________________________________
From: morphmet [morphmet_moderator@__morphometrics.org
<mailto:[email protected]>]
Sent: Friday, September 16, 2011 11:22 AM
To: morphmet
Subject: Re: idea about image acquisition
-------- Original Message --------
Subject: Re: idea about image acquisition
Date: Fri, 16 Sep 2011 14:08:41 -0400
From: Matt Burton-Kelly <[email protected]
<mailto:[email protected]>__>
To: [email protected] <mailto:[email protected]>
I use this method for imaging freshwater mussels for outline analysis.
It works great if you have specimens that don't have large
pseudocardinal teeth, which lift the one edge of the valve and
therefore
introduce distortion into the outline shape. That being said, I
haven't
tested how much distortion there is and whether it has any effect
on the
analyses.
Matt
On Sep 16, 2011, at 1:01 PM, morphmet wrote:
-------- Original Message --------
Subject: idea about image acquisition
Date: Thu, 15 Sep 2011 18:20:00 -0400
From: David Thulman <[email protected]
<mailto:[email protected]>>
To: [email protected] <mailto:[email protected]>
I have used a decidedly low-tech method for image acquisition by
using a
flat-bed scanner. I've used this for bifacial archaeological
artifacts
(but they have a lenticular cross-section that looks like a
fish). The
scanner I've used is an Epson 4180 Prefection (cost was less
than $100),
but most scanners these days with a CCD should work fine. The
scanner
has a depth of field of at least 1 cm, and probably more than 2
cm. The
error was less than .01 mm (tested with a digital caliper). The
images
were scanned at 600 dpi, which eliminated the need for a scale
for the
analysis I did. I used the images for a traditional morphometric
analysis (length, width, ratios, etc.), but recently uploaded
them into
tpsDIG2 and have started reanalyzing with GM.
Laying a fish on the scanner platen may get messy, but its an
alternative that should produce precise images at low cost and
fuss for
the right kind of specimens.
David Thulman
Department of Anthropology
George Washington University
