How much to shift?

One thing that comes up in stereoscopic scanning is how much to shift the object (or the scanner for the more abmitious!) between scans. This is similar to the question of how much to shift a camera when using the slidebar technique. The amount you shift will depend on the nature of the object being scanned, the optics of your scanner and your own personal preferences.

Smaller shifts produce very little parallax, with very little perceived depth whereas larger shifts produce greater parallax and thus greater depth. With small objects it is possible to greatly exxagerate the depth and thus produce wierdly distorted and sometimes disturbing images!

half inch shift

A half inch shift produces almost no parallax and although the object is behind a window, the depth of the object itself is so subtle most people won't notice.

A system of prisms and/or mirrors effectively places the object much further away optically than it is physically reulting in very little parallax at a half inch shift. JPS version

1 inch shift

One inch shift most people will notice the depth here, though it is still fairly subtle.

The optics of the scanner were designed to allow it to "see" the entire width of the scanner, but have the very useful side effects of greater depth of field and a reasonable amount of parallax for a given shift, both of which come in handy for stereoscopic scanning. JPS version

how it's done
Stereoscopic scanning
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1.5 inch shift stereoscopic scanning
1.5 inch shift getting there JPS
2 inch shift
2 inch shift sometimes ideal JPS
2.5 inch shift
2.5 inch shift my favorite JPS
3 inch shift stereoscpic scanning
3 inch shift nicely exxagerated JPS
4 inch shift stereoscopic scanning
4 inch shift usually too much JPS
4.5 inch shift too much!
4.5 inch shift Severe distortion,
sometimes disturbing JPS