Hi Giada, The object may simply be too small. However...
1. My recollection is that you need to keep your f-stop much lower, maybe f-11 maximum. Look into it. It's possible this has changed with recent software updates. 2. I assume each chunk is a rotation around the skull. Try shooting more than 3 rotations. For crania, I prefer 5. 3. How many photos per rotation are you using? For small primate crania, I have used as many as 35. 4. Sometimes dirtier skulls are better than clean ones. If the bones are bleached white, it will interfere with the ability of the program to identify specific points. 5. Sometimes a few photographs mess up the whole alignment. If you align each rotation individually, and your photographs are sequentially numbered, you may be able to pick out these photographs and remove them from the dataset. Good luck. David On Tue, Dec 13, 2016 at 6:02 AM, Giada Giacomini < [email protected]> wrote: > Hi all, > > I am quite new to photogrammetry and geometric morphometric worlds and I > got a bit stocked. > I am trying to build 3D models of insectivorous bat skulls employing > photogrammetry (more details at the end) and Agisoft Photoscan software. > The methodology works quite well with bigger specimens (19 mm x 12 mm x 7 > mm). > But with a smaller ones (e.g. 13 x 8 x 5 mm) the software has different > problems in the 3D reconstruction: usually it is not able to reconstruct > the dense cloud (doing “inside out” or providing a long scratch of points) > or, if the first step had worked successfully, it isn’t able to align the 3 > chunks together. > > The pictures are in focus and the specimens in the picture results big > enough I would say. > We are trying with other software different from Agisoft but the > reconstruction is still difficult. > > Anyone of you have already tried to perform photogrammetry on such small > objects? > Do you have any suggestions or comments? > > Many thanks > > Giada > > Photogrammetry equipment and camera settings: > Camera: NIKON D5300 (24 megapixel) > Lens: NIKON macro 60 mm, f2.8 > Settings: > 4-5 cm from the specimen > 100 ISO > f/32 > 0.5 sec exposure time > No flash. 3 white lights > Focus: automatic focus on a manual selected square > > -- > 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 [email protected]. > -- David C. Katz, Ph.D. Evolutionary Anthropology University of California, Davis Young Hall 204 ResearchGate profile <https://www.researchgate.net/profile/David_Katz29> Personal webpage <https://davidckatz.wordpress.com/> -- 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 [email protected].
