After reading a post on Google+, and checking out Robert Rath’s writeup of his Transit of Venus through-a-pinhole shot, I decided it was time to make a pinhole lens and see how the D7000 fared with an optic even more rudimentary than the Holga 60mm f/8.
Step one: procure supplies. In this case, supplies consisted of:
- two heavy-duty aluminum cake pans from a local grocer (I went with some rather expensive, fancy ones, as they had the flattest bottom)
- some black duct tape and/or black gaff tape
- a 52-55mm extension tube (roughly 50mm long, Fuji branded, from a kit that allowed me to attach filters to a really shoddy bridge camera I bought back in 2003, and kept for some reason when I sold off the Fuji camera)
- a 52mm Nikon-mount reversing ring
- a #10 sewing needle.
Total cost: maybe $3. The pie pans were $5; the reversing ring was $7; a roll of duct tape runs $3; a big collection of needles goes for maybe $2; and 50mm+/- of light-tight tube is maybe $3 (think “PVC pipe, cut to size”). If, like me, you already have most of the supplies laying about, the cost will be minimal. (My total outlay was $5.23 for the cake pans, and I have one and a half of them left over for some other project, or perhaps some cake-baking. It seems strange that you can’t buy just one heavy-duty aluminum pie pan, but you can’t, not at Kroger, anyway.)
Step two: cut out a piece of cake pan from the bottom of the pan, and poke a tiny hole through it. This is where every bit of sharpness and/or image quality will come from, so care must be taken to achieve the cleanest hole possible. Given that I used a sewing needle—versus, say, a laser—there was no way to achieve a perfectly round, smooth hole, but I did spin the needle as I poked it through to the desired depth (about halfway to the widest point), and continued to spin and sorta wobble the needle for a bit to make every attempt to remove as many little abraded bits as possible.
Step three: lens construction. I used black duct tape to enlarge the pie pan piece and create a sort of cap for the extension tube, then gaff-taped it all together. If I was less frugal, I would’ve used gaff tape the entire time, but my roll of gaff tape is somewhat less than 1″ wide, versus the 2″ of the duct tape, and I’m fairly frugal about most things, so…
Step four: mount your new lens, and try to figure out how to compose with an extremely dark viewfinder. If my calculations are correct—and given my maths, assume I’m way off—my pinhole lens has an f-stop somewhere between f/128 and f/180, so the viewfinder is completely black.
I used a flash-shoe-mounted bubble level to make sure the camera was plumb and square, took test exposures, and made smaller and larger adjustments until I found the composition. As the week went on, and I got some practice, this got easier.
Shutter speeds were in the 1/3 second range in full sun, and typically around 15 seconds for most shots. I held ISO at 100 for most of the week, but the pre-sunrise shots from yesterday morning’s Sunrise at White Rock Lake MeetUp photowalk (photos and a write-up to follow) required ISO1600. If I could’ve been bothered to pick up a fresh battery for the remote, I would’ve used bulb mode and and a two or three minute exposure for the “Knot’s Landing” sunrise picture, but, alas, I’m sometimes lazy about things like that.
I’d like to find a laser-cut piece of brass if I try this again, or maybe cough up the $50+ for a body-cap pinhole lens from Photojojo or somewhere. The latter is tempting, despite its expense, due to the ever-increasing dust-spot remediation I had to do on every picture: shots from the first day had no visible dust spots; shots from day 3 required maybe a minute of dust duty; shots from yesterday (not used) were given up on. Thankfully, my sensor cleaning operation is up and running, and it only took maybe 3 minutes to clean the dust off the sensor. In either case, some sort of manufactured hole will be required if I want results much sharper than these: I’m not sure that I do, to be honest, but I sorta do.
D7000. Homemade ~40mm f/128 pinhole lens. 5 shots at ISO100, 1 at 200, and one at 1600; speeds from .6 to 30 seconds. I increased contrast, boosted highlights, and messed around with shadows, whites and blacks, and increased clarity, saturation, and vibrancy on pretty much every shot in Lightroom. Total time from import to upload: less than an hour, including selection and processing, so maybe 2 minutes per image.