Last week I was given some bits and bobs from a scientific darkroom that shut down at the university once the researchers had converted to a fully digital workflow. One of the items was a box of Kodak Electron Microscopy film (SO-163, if anyone is interested).
The film comes in the unusual size of 3¼×4″, which apparently is standard for electron microscopes. That sounds very close to the quarter-plate format which is nominally 3¼×4¼”. I was delighted to find that the film fits exactly into the holders used in my Lancaster Instantograph, dating from the 1880s or 1890s. This means I now have a supply of film that fits this camera natively, rather than having to cut down 5×4″ film in the dark with a guillotine. What could possibly go wrong?
This Electron Microscopy film is designed to be exposed by a beam of electrons, not by visible light. I could tell it would be at least somewhat sensitive to light by the fact that the box says only to open the film in the darkroom, and to use a red safelight. This implies that the film is sensitive to blue light only, i.e. it is orthochromatic.
As the film is not intended for use with visible light, no information is available about its sensitivity (film speed). I did some boring exposure tests in my living room, starting with the assumption that it was ISO 25. This produced a slightly underexposed image, so I tried again at ISO 12 and got a good exposure.
The Instantograph has a fixed lens which is a 5″ single achromat. It has a focal length of 127mm and boasts two uncoated elements and an aperture that varies between f/10 and f/30.It lacks a shutter, so exposure is controlled by removing the lens cap. Pretty high tech stuff for its day, back when Queen Victoria was on the throne.
This frame was exposed at ISO 12 for 8 seconds. Aperture was wide open at f/10.
I developed in Ilford PQ Universal for 2 minutes. This does seem quite a short development time but the density of the negative is good, the grain is fine and the contrast is strong. Given that this is a very old lens shot wide open, the sharpness goes right into the corners and there is hardly light fall-off. PQ is know for its high contrast, so in future I will try other developers such as ID-11.
Having established ISO 12 as a reasonable starting point, I ventured out onto Troopers Hill and exposed two frames there, too. The light was much brighter so this frame was exposed for a mere 2 seconds with the aperture fully stopped down to f/30. I must have bumped the camera when removing or replacing the lens cap, because this image is a bit unsharp.
Even so, it is obvious that this is an excellent lens–not only for its day, but still outperforming many inexpensive SLR lenses made a hundred years after it. It would definitely blow any smartphone camera out of the water. It is probably the case that the film’s lack of sensitivity to red light means that the visible effects of chromatic aberration are reduced.