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Author Topic: Small Tie points and bumpy surface by heads  (Read 849 times)

scr1tch

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Small Tie points and bumpy surface by heads
« on: December 07, 2017, 06:28:58 PM »
Hello everybody. I have problems with the scan of a face. The surface is very bumpy. Short to the equipment:
Sony Nex 5n, cheaper Chromakey, softboxes for lighting.
I only use manual focus. The photos are so beautiful with 16 megapixels that I can recognize individual pores when zooming in. Lack of sharpness is not the problem. After shooting the pictures I increase the contrast and create masks in Photoscan.

In order to shorten the computing time for my tests, I work with only four photos, which is sufficient to calculate the front of the face. When I start aligning the photos, I only get ~ 600 tie points. In a test with a porcelain figurine, there are also 4 photos over 6000! How can this discrepancy come about? And why are the surfaces of the head so bumpy?

Alexey Pasumansky

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Re: Small Tie points and bumpy surface by heads
« Reply #1 on: December 08, 2017, 09:54:21 PM »
Hello scr1tch,

Are you pre-processing the images? It seems that EXIF information is lost for the photos from the first chunk. Have you tried to process the images "as is"?

Another possible reason of the issue could be small movements of the scanned person during the shooting session.
Best regards,
Alexey Pasumansky,
AgiSoft LLC

scr1tch

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Re: Small Tie points and bumpy surface by heads
« Reply #2 on: December 09, 2017, 02:18:30 AM »
Hello. The pictures do not have their metadata in the mentioned test. I have now scaled down the images to 1MP and tested them again, and so I get much better results. how can that be?

Alexey Pasumansky

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Re: Small Tie points and bumpy surface by heads
« Reply #3 on: December 11, 2017, 10:13:57 AM »
Hello scr1tch,

If there were even small movements of the person during the scanning procedure, then higher accuracy used during the Align Photos operation will be more sensitive to those movements. Lower accuracy (that is using downsampling the source photos) is less sensitive.
Best regards,
Alexey Pasumansky,
AgiSoft LLC