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Re: [Phys-l] half lens



Anthony Lapinski wrote:
.... "photo divider," which attaches to the front of
the lens and can rotate. So one can do double exposures of half a scene at
a time. Wow!

The divider needs to be a long way in front of the center of the lens.

Note that the optical center of the lens on an SLR is waaay inside the
lense structure.

========

As another example of the same thing, you can put tape over half of
each lens in a pair of eyeglasses. This will block about half the
scene.

Again, for a compound lens, the frontmost piece of glass can be
waaay in front of the optical center.