-------- Original Message --------
Subject: RE: idea about image acquisition
Date: Mon, 19 Sep 2011 11:36:03 -0400
From: Sheets, H David <[email protected]>
To: [email protected] <[email protected]>
I keep meaning to dig up some references on scanners and specimens with
some degree of relief, by which I mean specimens that do not lie
perfectly flat on the scanner surface, but have some structure
perpendicular to the scanner bed. But other aspect of life keep
intruding, so here are some unreferenced comments, I'll try to do better
later.
Anecdotal, it is important to check the behavior of your scanner in such
a case, in some cases the distortion due to the sample's perpendicular
structure may depend somewhat on the sample position on the scanner.
This effect obviously won't be visible if you place a piece of graph
paper on the scanner, one approach to checking this issue on a given
scanner is to scan a set of machine nuts placed at different locations
on the scanner simply to see if the z-axis distortion varies with
position. Again, anecdotally based on the performance of some
scanners, this effect seems to be minimized by placing specimens in the
center of the scanning plane.
If your specimens are perfectly planar, this obviously isn't a concern.
If you have much relief, it might be worth a quick look at this.
-Dave
H. David Sheets, PhD
Professor
Dept. of Physics
Canisius College
2001 Main St
Buffalo, NY 14208
-----Original Message-----
From: morphmet [mailto:[email protected]]
Sent: Monday, September 19, 2011 11:12 AM
To: morphmet
Subject: Re: idea about image acquisition
-------- Original Message --------
Subject: Re: idea about image acquisition
Date: Mon, 19 Sep 2011 05:15:00 -0400
From: marta rufino <[email protected]>
To: [email protected]
Hi,
I have been using this method for while now. It works very well- for me,
much better and simpler than the camera.
Still, I always check for distorsions before I use the scanner.
Cheers,
M.
2011/9/16 morphmet <[email protected]
<mailto:[email protected]>>
-------- 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
--
//*//Marta M. Rufino*(investigadora auxiliar//| bióloga marinha//| PhD)//*/
____________________________________________________
/**CIIMAR **//*(Centro Interdisciplinar de Investigação Marinha e Ambiental)
*DGM *(Departamento de Geologia Marinha), LNEG (Laboratório Nacional de
Energia e Geologia)
Estrada da Portela, Zambujal - Alfragide
Apartado 7586, 2720-866 Amadora
Portugal
