notes.husk.org/likes images.

When I made the pinhole for my A7 first walkabout yesterday, I didn’t go overboard with being super careful. The Wanderlust folks use semiconductor grade etching to make their pinholes as round as possible. Many of the how-to guides out there will instruct you to dimple a sheet of metal and then sand it down to achieve a reasonably round hole. My method was fairly barbaric in comparison: I taped a piece of aluminum foil to the inside of the body cap that I’d drilled the center out of and used the smallest needle I could find in my bathroom drawer to punch the final hole.

The result is pretty good, but it’s not perfect. In particular, the edge of the hole is a bit ragged. This has an impact on the light passing through the hole, as you can see from the flare in the top photo above. In particular, check out how the flare is interleaved—which seems to me to be the light being affected by the rough edges of the hole.

I sent the photo to Bryan Jones—who has much better chops when it comes to understanding photons than I do. He said:

This is a perfect demonstration of chromatic aberration or color fringing. Essentially, the different wavelengths of light are being bent at varying angles. The shorter wavelengths (green) are first, followed by yellow, orange and red. Normally, optics correct for that sort of thing, but seeing as how there are no optics…

It’s not a bad pinhole all things considered. The other thing might be to adjust the distance. It might actually be too close to the sensor. Do you have any extender tubes you can mount in front of the body cap?

The E-mount has such a short flange distance that it might indeed be too close. When I get a chance, I’ll likely give putting the foil on the outside of the body cap a try—though the assembly will be super delicate at that point. I might also try to play with some tubes. But, my 35mm lens is on a delivery truck as of this morning, so I might not get to it quite right away.