Chronology Current Month Current Thread Current Date
[Year List] [Month List (current year)] [Date Index] [Thread Index] [Thread Prev] [Thread Next] [Date Prev] [Date Next]

Re: split lens





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.

Doing this at the film plane is the hard way. It is regularly done with a 35
mm camera by placing a card just in front of the filter. At the numerous
Nikon Schools of photography that I have attended, the instructors have
shown how to build a cheap card holder to mount on the lens so that the card
can be moved, blocking out different areas, for interesting effects.

Roger