Funny you asked. I'm in the middle of a scan and I have a theory of sorts. It has to do with the sharpness and the resolution of the scanner. I think it's like anti aliasing on videogames. With low resolution lines at an angle to the pattern of the screen the line will appear jagged. These jagged lines will translate into your scans when the scanner thinks those are smooth lines but in reality they aren't and the program things you have a raised surface. This sort of coincides with the raised lettering on high contrast labels like @This talked about. I'm also thinking that this would happen on deep surface scans. So I think if we had better projectors in the scanner not only would our scans be better but we would also get rid of these wavy lines. This kinda of also goes along with the cameras too. Look at these scans and a picture of reality with the crosshair. You'll see sort of like 8bit lines when the line should be a smooth vector.
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