Wednesday, January 18, 2017

Instax Hacks

In a quest to get back into film photography, I spent a long while lusting after vintage SLR like a Nikon FM-2 or Canon AE-1. My motivations were mostly boredom and nostalgia. I eventually came to the realization that I enjoy sharing my photos, and that the world has gone digital. The prospect of digitizing film made me remember days of scanning negatives and prints of old family albums. It was awful. I'll stick with my digital bodies.

My modified Fujifilm Instax Mini 8 with its new tripod socket and remote shutter release
Enter instant film. I mostly use it to give out instant souvenirs at social events. The current market for self developing film is dominated by Fujifilm's Instax line. The typical "mini" version is 54 x 86mm, 800 ISO, color film. There is a variety of cameras to choose from, but I settled on the cheapest bare-bones unit knowing I would tinker with it. Also, the reviews for the fancier ones were plagued with electronics failures.

Mini 8 circuit board
The Mini 8 has a 60mm prime lens (single element plastic optic) and a mechanical shutter fixed at 1/60s. Aperture is a user-selectable rotating plate with different holes for f/12.7, f/16, f/22, and f/32. Flash is compulsory. I used the Mini 8 for a while but wanted additional functionality: 1) tripod mount, 2) remote release/timer, 3) flash control.

New tripod socket
My tripod mount is a 1/4-20 tee nut. I found some void space and step drilled a hole in the body to slip fit. I pinned it with one screw then epoxied it all in place. Goal 1 accomplished.

The camera is driven by a single hobby motor. A rather complicated gear, lever, and cam system cycles the shutter, flash, and film rollers.

Opened Mini 8 with new leads on the flash switch and shutter switch
The shutter release button is a single pole single throw switch. I tapped the circuit by soldering wires to the corresponding pins on the PCB. I had to map the pinout by visually tracing wires and checking continuity with a multimeter. Most of the exposed leads are for various switches.

I decided on 3.5mm audio jack as my port because it's compact. I rigged up a push button SPST and housed it in some PVC fittings. The cable is a 3.5mm stereo patch cord. Depressing the push button closes the "SP" circuit to begin the shutter cycle. I still need to rig up some kind of timer, but the hard part of getting the signal out of the body is done.

Custom remote release, connects via an audio cable
An intervalometer with Canon pinout, plus a 2.5mm to 3.5mm stereo adapter
Canon shutter remotes happen to use the same stereo pinout that I chose. Adapting an off-the-shelf intervalometer turned out to be the best way to get timed release.

I thought I could toggle the flash by interrupting the "SSY" switch. That's the circuit triggered during shutter opening. I think the SSY circuit ground clamps, because cutting the SSY leads didn't stop the flash from firing. I couldn't interrupt the high voltage side of the flash capacitor (I don't think I could fit an appropriate 320V switch into this little body). I would have cut off the 3V side, but there are some charging electronics and sensors that probably would have disagreed with my meddling. I'll leave this issue for another intrepid individual.
Fujifilm Instax Mini 70
Or maybe I should have just bought an Instax with built in tripod socket, self-timer and flash control...