A story of amazing proportion

Back in the Awkward Years (1960-1984) we used to make paste-ups, then photograph them on large process cameras to make large sheets of film from which aluminum printing plates were made.

Photographs were handled separately from line art, and the resulting films were hand assembled on a light table on separate overlays of acetate film held in position by register pins.

This may sound like a scary story that is told around the campfire at camp, but it’s true.

One of the essential tools of the trade in those Awkward Years was the circular calculator, also known as a Proportion Wheel. This is a circular slide rule with geometric markings. On the outer wheel is the final size in inches (I’m sure these things exist with metric measurements); on the inner wheel is the current or original size. When you look in the little window, you see the percentage at which to shoot the photo of the art to get it the right size to put into the film.

There is also a scale indicating the reduction factor, a value I never found valuable.

When reducing an image to a smaller size, the percentage is critical. We used to fudge this a bit to prevent trouble on the light table. We would routinely shoot halftone negatives about two percent larger than the proportion wheel indicated. This caused trouble occasionally, when we would crop-off some guy’s ears, but most of the time it helped to prevent gaps in the photo, and thus reshooting the halftone.

My cameraman, a wonderful man named John Flynn, shot every halftone five percent larger than indicated by the artists. He found that he had to reshoot fewer photos that way. We seldom noticed. That’s part of the reason I call this era the Awkward Years.

I was reading an issue of Communication Arts magazine in 1985 where the publisher, Richard Coyne, described how his magazine had a machinist make a special proportion wheel with a machined vernier scale mounted on it. He commented on how the magazine had such tight tolerances that they needed such a precise scale.

What he was missing was that a proportion wheel is performing long division. And, long division can also be done with a pencil on a piece of paper, or on one of those newfangled pocket calculators. Imagine that!

The formula for proportion is really simple. It’s:

and any pocket calculator will give you the percentage to several digits of precision. The other advantage of using a calculator is that once you have the percentage you can multiply it by the other dimension of the photo to ensure that it fits its window.

It’s amazing how math works!

Of course we never use these proportion wheels today. We just put the photo into a window on the page, and we scale it to fit while holding the shift key down to maintain proportionality. And, when it fits, we let go.

It’s not as awkward as it used to be. Thank goodness!

About Brian Lawler

Brian Lawler is an Emeritus Professor of Graphic Communication at California Polytechnic State University, San Luis Obispo and was a Guest Professor at Hochschule München from September, 2021 to September, 2022. He writes about graphic arts processes and technologies for various industry publications, and on his blog, The Blognosticator.
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