Re: How do you test if camera lenses match?

[P3D Sam Smith <3dhacker@xxxxxxxxxxxxx>]

At 11:56 AM 10/3/97 -0600, you wrote:
>What I am trying to do is use two (or more for lenticular) lens/shutter
>combinations from the same type of beat up Autographic 3 cameras
>to make a stereo camera....  

>The reason I didn't want to use film is because I don't have the camera
>made yet and want to see if the lenses I have are matched closely enough
>for me to even bother.

A can understand not wanting to use an entire roll of 120 film just to test
a lens. Are the autographic cameras still intact, or have you already
started to hack them?

Have you considered making paper negatives with standard B&W photo paper?
You can't beat this for a low cost alternative. Just cut a sheet ( under a
safelight of course) to fit the film area, and exposure it at an ISO of
around 5.

When I'm testing lenses these days, I first have to determine that the
camera is correctly focusing at infinity. This is critical, as if your focus
is even a little bit of the image size will change. I now do this with a
home-made collimator. A ground glass is not as accurate, but if it's all
you've got it will have to do. Next I have to assume that the focusing scale
is accurate. I tape a full newspaper page to an indoor wall, and frame it
through the back of the camera. Make sure it's close enough that print show
on all edges. The camera must be on a tripod and perpendicular to the paper
target. Calculate the exposure and photograph it WIDE OPEN. This will tell
you not only how good your lenses are and how carefully you focused, but buy
measuring the distance between the features on the newspaper carefully you
will have something to compare. Put the second camera in the exact position
and do it all again.

If the lenses are too bad to see the edges clearly you'll have to stop down.

The rest is math.


Sam


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