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Author Topic: Need advice on some turntable-scanning  (Read 2206 times)

Phish

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Need advice on some turntable-scanning
« on: January 27, 2017, 02:43:25 AM »
I have a prob here, I used a turntable (actually one for cakes) with light green cut to fit the diameter. Same cloth was used for the background. It works nice eg. in After Effects, but I get no results in Photoscan at all.

I use a Canon EOS 650D on somewhat low ISO-settings (as low as I can go with the lighting here, mostly ISO100-200) and shoot in RAW. In Lightroom I just make sure that all photos have the same exposure and export them as TIFF. At the turntable I have two LED-lights placed at the 4 and 8 oclock-positions to light the figure up.

I also removed manually the background in Photoshop and saved the photos with alpha-channel as TIFF, just for a test, but I get the same static pointcloud:



I don't understand what I'm missing here? Are my photos that bad?:



Fullsizepic: http://i.imgur.com/D872Q8r.jpg

kind regards!

Alexey Pasumansky

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Re: Need advice on some turntable-scanning
« Reply #1 on: January 27, 2017, 12:24:19 PM »
Hello Phish,

I think that the main reason of the problem is related to the lack of the texture pattern of the scanned object - many areas with almost no distinguishable features. Additionally there are blinks and reflections on the surface which positions are different for each rotation angle, so they induce additional confusion.
Best regards,
Alexey Pasumansky,
Agisoft LLC

jonc

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Re: Need advice on some turntable-scanning
« Reply #2 on: January 27, 2017, 03:22:34 PM »
I'm pretty new to this (2 weeks in) but I've a couple of tips that may help:

Your light is too harsh, bounce it off the walls or white card, I've found if I can see hard shadows and sharp hilights it's not going to happen.

More varied angles in your photos, do at least a low, mid and high pass of your turntable and get in closer to your subject.

I've seen online, though not tried it myself, that sprinkling the subject with talcum powder or just painting it matt will help. Of course you are sacrificing the texture capture doing this but it's quite a simple colour job anyway.

Phish

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Re: Need advice on some turntable-scanning
« Reply #3 on: January 28, 2017, 10:52:49 PM »
Hello Phish,

I think that the main reason of the problem is related to the lack of the texture pattern of the scanned object - many areas with almost no distinguishable features. Additionally there are blinks and reflections on the surface which positions are different for each rotation angle, so they induce additional confusion.

Thanks for your reply.

I tried it in bright daylight already walking around the figure... didn't work either.  What makes me wonder is the point, that Photoscan doesn't detect the "movement" around the figure if I use the turntable. Looks like the mask is not working properly?

About the reflections: already used paper in front of the LED-lamps... I still got the reflections... the material is kind of very reflective...