DIY Pinhole Lens
New Pinhole Lens!
Somehow I found the time this weekend to work on my new pinhole lens design. I used one of the extra disks I had from the first design that I sanded to fit inside the T-Mount adapter. I got some more 0.020 in thick Aluminum from my dad, but realized that it is too thick. The Halloween edition mini 7-Up can came in handy as I cut part of the side out and then cut it into a circle. To make the pinhole, I took a thumbtack and punched a very small hole into the aluminum. After epoxying to the back of the wooden disk, I let it cure for about an hour and a half before I felt confident it was fully set.
Material Used:
- Scrap Aluminum from Soda Can
- 1.95 OD Black Walnut disk 1/4 thick
- T-Mount to K-Mount Converter
The pinhole itself is smaller than a #80 drill bit (0.343mm), so I’m pretty excited there because the #80 drill bits I have are a pain to use and I’ve already broken one. — Will have pictures of this soon.
Old Design
I was wondering through my home office (crap storage area) and saw my attempt at taking apart an old SMC Pentax-M 80-200mm f/4 telephoto lens. The goal was to fix the dent in the outer barrel that controls the zoom and focus of the lens. I had a hell of a time getting it into two separate pieces, the front element section/barrels and the lens mount section.
So I’m looking at the two pieces of the lens that are sitting on a plastic bag and realized that I should use parts of it to make a DIY Pinhole lens. Brilliant idea I thought; all I had to do was free the bayonet mount (K) of the lens off the aperture ring. That proved slightly difficult without a JIS screwdriver set.
Material Used:
- Scrap Aluminum: 1×1x.05
- 2.25 OD Black Walnut disk 1/4 thick
- Lens bayonet mount – from old K-mount lens
- Qty 5 0-80×3/8 machine screw
- Qty 5 #0 Flat Washers
- Qty 5 0-80 Nut
The lens parts
The actual metal part of the mount I pulled from the 80-200mm lens has a small lip on the edge giving an inner diameter of 2.25in. The plan in so put a wooden disk inside that ring to provide a “body” of sorts to the lens and I just happen to have extra 3/8in pine board left over from building the Pano Head. My friend Eric suggested I find an exotic hardwood to make the lens classy, after I said I was going to stain the wood to make it look good. It turns out, a guy in my old group at work is a woodworker and has a lot of scrap lying around and from that, he got me a piece of black walnut 2.25in disk 0.25in tall with a 1/2in hole in the center. I don’t have the tools so it would take more time trying to figure out how to get my piece of wood cut than asking him for a piece of his scrap that he can fabricate for me.
In the wooden disk, 5 through holes are drilled to mount the disk to the bayonet mount; these holes line up with the holes in the metal mount. The scrap aluminum piece has a 1mm hole drilled in the center as the pinhole. I used a size 60 drill bit which was the smallest I could buy from Ace Hardware, which is where I got the machine screws. The picture below shows the aluminum piece epoxied to the back of the wooden disk.
Pinhole attachment with 5 minute epoxy
The next two pictures show the completed lens, front and rear views. The machine screws attach to the lens mount and go through the disk and are fixed with a washer and nut to tighten down.
Front of completed lens
Rear of completed lens
All I need to do now is figure out the aperture of the pinhole and work out some standard exposure times.
After some test shots, it is apparent that a 1mm hole is way too big and the shots come out blurry. I’m working on a way to get a smaller hole, and possibly a better mount idea. The T-Mount to K-Mount adapters have an inset that is held by set screws, all one needs to do is make a disk to fit and secure with the set screws. That is my next task since a friend has let me borrow a T-Mount adapter.
