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Re: split lens




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REPLY FROM: Quist, Oren Phys


On Fri, 21 Jun 1996, Quist, Oren Phys wrote:

the half-covered lens is sort of a minor thread on the list, but I couldn't
help but comment.

Professional photographers use this technique often when photographing
weddings.
They cover the top-half of the lens and photograph the happy couple
at the altar, or kneeling, or some solemn moment.

The shutter is reset without advancing the film. Depending upon the
camera, one can hold in the bottom rewind button while advancing the
film, or rewind the film one frame after the camera has set itself
for the next picture.

Then the bottom half of the lens is covered as a second picture of
the church steeple, or stained glass window, or church front, or
whatever it taken.

The net result is a superimposing of two images that is very effective and
difficult to do by other means.

This is clearly an optics effect that is more hands-on, or emperical, than
theoretical.

I am a physics teacher with photography as a recreational interest.
The above explaination of split image photography is not correct.
The photographic process mentioned involves blocking the image formed by the
lens (half lens or otherwise) at the film plane. A large format camera is
required to pull this off.
Physics teachers commonly use a plastic lens, that is sawn in
half, to demonstrate the error in the misconception of 1/2 lens = 1/2 image.
When an image of a lighted candle is projected on a small screen, then
half of the lens is removed, the resulting image remains whole, but is
half as bright.

Say what you want, but it works!

It works best with a large format camera -- I have done it with a
2 1/4 x 2 1/4

but, I have also done it with a 35 mm SLR by simply holding my hand
over the top or bottom half of the lens. Note, the entire image will
be present, but a major part of it will be much dimmer than the rest.
This allows for the superimposing of two images on different parts of
the negative.