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Posts: 2,050 | Thanked: 1,425 times | Joined on Dec 2009 @ Bucharest
#10
Originally Posted by TiagoTiago View Post
How bad the scan of a face would be for example?
Even at very close range, the focus of the camera is in 10 cm steps. With perfect focusing and perfect calibration, you need 10 cm high features to register. Your face will be flat. Also, because the face loses contours as you go away from center, it will probably have one more lock point at the edge and then it would be "background".

I'm guessing it'll be a round disk, 10 cm high, sitting on a background that is "far away".

Oh, and, there's also the issue of not every scan actually having sharp edges. The tip of the nose, e.g., has no edges unless you can detect imperfections of the skin of the tip of the nose. You can't do that with an N900 camera. Even a DSLR would have trouble with that. The next centimeter will lock to the eyes, likely. Next few centimeters will also lock to the eyes. Further away, it will lock on hair, ear contour, etc. So even with a DSLR and 1-cm locking precision, you're unlikely to get anything over 5 levels out of a face. Think LEGO, but with big blocks.

And then there's the issue of the DOF (Depth of field). At 50 cm, DOF is at least 20 cm with a camera the size of N900's. That means that the whole face will be in focus. And with no physical aperture control, DOF can't be controlled.

At the said range, a DSLR with a high aperture would be lucky to get 3 shots that have a different focus line. Multi-focus techniques (focus stacking) for snapping angled (45 deg) miniatures rely on a 3-shot baseline. So even with true equipment, it's unlikely. The aperture necessary to get DOF in the order of centimeters at a decent distance is well outside camera range. We're talking flatbed scanners.

All this ignores the fact that it's not useful if you have to hold the camera in contact with a person's nose. To get their head in the frame, you need at least 30 cm distance. This limits your focusing ability to 40 and 50 cm before there is nothing to measure.
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N900 dead and Nokia no longer replaces them. Thanks for all the fish.

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Last edited by ndi; 2010-11-15 at 02:21.
 

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