The White River and Northern Model Railroad: Clinic

	The N Scale

	Model Railroad

Pinhole Photography

A Retrospective, Part 2 of 2

Contrary to common wisdom on the subject, pinhole size is not the only factor governing image clarity. It has been determined that irregularities along the edges of the hole itself contribute to the lack of sharpness. Such flaws can be microscopic and still cause problems. The more irregularities that exist, the softer the image will be, and since there is no practical way to produce a "perfect" pinhole oneself, it is an inescapable problem.

Recent technology has offered a solution: laser-etched pinholes that are virtually perfect, making hole size the only factor governing image sharpness. Still, there is a point where the pinhole becomes impractical to use due to absurdly long exposures; when one is using color film, reciprocity (color shifting) becomes a big concern—not to mention melting models under hot lights!

Thirty-odd years after my first crude pinhole photographs, I started experimenting with laser pinholes on the WR&N IV. These pinholes are quite affordable (about $30 each from Edmund Optics), and with the availability of some dirt-cheap used 50-mm lenses from a local camera shop, I decided to crack one open and place the pinhole where it belonged—in the aperture plane.

The pinhole itself is perfectly suited for the application: the hole is etched in the center of a small circular stainless steel disk, the outer dimension of which is smaller than the lens aperture when fully opened. By suspending the disk on a set of "spider legs" (thin brass strip stock), I could then compose the image in the camera by fully opening the aperture, then stopping it back down for the exposure.

My initial experiments hinted at some exciting possibilities—except that my arbitrary choice of pinhole size (300 microns) could not quite get me the depth of field I sought. Thus foreground objects less than about three inches from the lens were out of focus.

Despite this great learning experience, my travels down this road have come to and end, and not because the WR&N IV no longer exists. No, the reason all of this is now history is because of the tremendous advances in digital photography, which are covered in another clinic.

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