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Re: half lens



On Fri, 21 Jun 96 14:30:34 MDT Alex. F. Burr said:
The half lens thread is interesting. Try the experiment with a simple
lens. You do NOT have to split the lens to observe that a full image
is obtained with half or more of the lens covered. The image intensity
is just reduced.
-
The image intensity is not reduced evenly. If you draw a diagram I
think you will see that in order to reduce the intensity evenly any
obstruction must be placed in the plane of the optical center of the
lens. This is why any diaphram or shutter in a lens needs to be placed
somewhere near the optical center of the lens.