Dear Anderson Feijo, I assume that the difference is not a matter of scaling (that could be addressed with the Procrustes superimposition), but one of optical distortions caused by the lens. This paper exemplifies this for different lenses: http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0149313 <http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0149313> Likewise, to minimize optical distortions with a small focal length you would need to enlarge the distance more than sharpness allows. If you have the possibility to use a 3D Scanner or photogrammetry, you could then set the viewing setting to “infinity” instead of mimicking a rather short lens for digitization.
Best wishes, Sonja Windhager — Dr. Sonja Windhager Department of Anthropology, University of Vienna (Lecturer) and Department of Theoretical Biology, University of Vienna (Postdoc) Althanstrasse 14, 1090 Wien, Austria http://homepage.univie.ac.at/sonja.windhager/ <http://homepage.univie.ac.at/sonja.windhager/> http://theoretical.univie.ac.at/people/windhager/ <http://theoretical.univie.ac.at/people/windhager/> > On 29 Dec 2017, at 10:18, Anderson Feijo <andefe...@gmail.com> wrote: > > Hi everyone, > > I am starting a new project using GM which I will work with groups with > different sizes (e.g., rodents and small carnivores). I would like to find a > way to use the whole dataset in the analyses, instead of perform set of > analyses for each sized group. So, I did a test using one skull and place the > camera in two different distances to the object (~15 cm and ~30 cm). My > expectation was after scaling (using tpsDig) I wouldn´t have any meaningful > difference. But I got two clear groups that were statistically different. So, > my question is how can I combine 2D landmarks based on photos taken from > different distances of the camera to the object. I have attached here the tps > file (10 copies of the same skull, five at ~15cm and five at ~30cm). I would > be very grateful for any suggestion. > > All the best and Happy 2018! > > Anderson > > -- > MORPHMET may be accessed via its webpage at http://www.morphometrics.org > <http://www.morphometrics.org/> > --- > You received this message because you are subscribed to the Google Groups > "MORPHMET" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to morphmet+unsubscr...@morphometrics.org > <mailto:morphmet+unsubscr...@morphometrics.org>. > <Test-Scaling.TPS> -- MORPHMET may be accessed via its webpage at http://www.morphometrics.org --- You received this message because you are subscribed to the Google Groups "MORPHMET" group. To unsubscribe from this group and stop receiving emails from it, send an email to morphmet+unsubscr...@morphometrics.org.