Two Seeds

One you've seen before; for the other, a first brush with Facebook Fame

I tested a very different sort of lens today for macrophotography: a TV-camera lens.

WUT, you say?

Let’s back up a few steps. There is a category of lenses that most of us have not heard of, including me: line-scan lenses. These are extra-special-sharp lenses that are mostly used for industrial imaging. They are sharp so they can do things like read bar codes, measure the size of objects coming off a manufacturing line, count things, etc.

This particular lens is a Pentax 35mm f/2.8, which just happens to have a Nikon mount because the Nikon F mount is a common one for industrial cameras. But it also made it easy for me to test on my Sony using a Nikon/Sony adapter.

I got the detailed specifications for the lens from the Pentax TV lens catalog, but this and a few other lenses are in a separate section for line-scan lenses. The specs are really nice to have: sharp down 7 microns, for example, and with a large image circle of 45mm (significantly bigger than needed for 35mm format photography, but a big image circle is handy to avoid things like vignetting).

The test images showed it to be a really sharp lens generally. It would actually be a good general purpose lens for that reason, although it is manual focus so it’s not really an every-day lens. I added some spacers to make it more of a close-up lens (and that may well have been how it was set up when it was used as a line-scan lens, but I’ll never know…)

The photo above was taken with out 16mm of extra space to enable the lens to focus more closely. The sharpness is obvious. The seed pod on the left (doing an impression of a deep-sea fish of some kind) was previously images with a microscope objective at a much larger scale. The seed pod on the right (rocket-ship impression) was just hanging around, and the fine hairs and details are well-captured by this very cool find. Magnification was about 2x. (They were about twice life size on the CCD sensor.)

(That rough-looking surface is actually very finely sanded plywood that looks really smooth to the naked eye.)