terraPin ACME 6X6 (6x9, 6X4.5) Pinhole Cameras - 120 film

by schlem, published

terraPin ACME 6X6 (6x9, 6X4.5) Pinhole Cameras - 120 film by schlem Aug 26, 2016
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The terraPin ACME pinhole camera is the culmination of years of 3D printing and camera design work. This camera is assembled WITHOUT ANY FASTENERS, using sliding joinery. With the exception of the pinhole (which is easy to make), all parts can be 3D printed.

A "Better Cap Plate" for the ACME has been uploaded. I have added a snap clip to the sliding parts that eliminates the need for an arched clip to hold the cap together. As before, you will need to remove the support under the rectangular insert, where the winders fit. If there is interest, I can modify the caps for the ACE and CAMEO.

The terraPin ACME uses medium format 120 film, which is widely available at photography supply shops and on the internet (Amazon, Lomography, eBay, etc). The format is a square 6X6 frame (12 per roll of film), and the photos produced have a classic wide-angle pinhole look with peripheral vignetting (darker corners, brighter center).

Pinhole Diameter: 0.22 mm
"Focal Length": 25.4 mm
F-Number: f/135

I archive all photos I shoot with this camera on Flickr.

Also included in the downloads is the ACE (f/135), a smaller 6X4.5 version that shoots a rectangular frame and makes 16 exposures per roll of film. A new 6X9 version, called the CAMEO, has also been included. The CAMEO will have extreme vignetting due to the short "focal length" and wide frame. Shoot the CAMEO at f/165, like the MUTO or terraPin 6*6. See MUTO for examples of this vignetting. Exposure calculations available in Thing Files.

See terraPin High-Strength Winder (1/4" shaft) for additional winder/knob options!

Hey! Read This!
This work is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.
You are free to:
Share — copy and redistribute the material in any medium or format
Adapt — remix, transform, and build upon the material
for any purpose, even commercially.
Under the following terms:
Attribution — You must give appropriate credit, provide a link to the license, and indicate if changes were made. You may do so in any reasonable manner, but not in any way that suggests the licensor endorses you or your use.
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Print Settings

Printer Brand:




Doesn't Matter




0.25 mm layer height


50% - 90% depending on part


The vertical dimensions are precisely set for a layer height of 0.25mm


What To Print

The most important part of printing this (or any) pinhole camera is using filament that is opaque. PLA is often translucent, but THIS TOOL allows you to evaluate the opacity of your chosen filament.

Prototypes shown were printed in MatterHackers PLA. If you cannot find opaque black filament, consider other dark colors.

You will need to print:
A body plate
A cap plate
The film clip
(Knobs and winders)

The body plates differ only in details of ornamentation; pick your favorite. I like to print at at least 50% infill for strength and opacity. This is a functional camera that could potentially last for decades - print for the long haul.

The cap plate for the ACME requires support for an overhang in the cap insert. There are two versions - a plain version that will require your slicing software to generate support structures or a version with support that I designed for easy removal. I found that Slic3r, for instance, puts too much support under the overhang which greatly complicates post printing finishing. Again, print for durability - at least 50% infill.

The film clip should be printed with high infill for durability, and the dimensions of this part typically generate density from slicing software.

There is a set of knobs and winders that are completely 3D printable. The winder must be densely printed - I use 95% infill - and WILL NEED SUPPORT. The knobs can be somewhat less dense, but at least 50%.

Lately, I've been using instrumentation knobs for my cameras, and if you like that idea, you have a couple of options. The winders_alt can be 3D printed (95% infill) WITH SUPPORT. Or you can order a set of winders from Shapeways in nylon or stainless steel. "Instrument" or "Control" knobs should be for 1/4 inch (6mm) shafts and should have a set screw. Radio Shack, Fry's Electronics, or Mouser are good sources. Electric guitar control knobs look nice also. Find these at a shop like Guitar Center.

Finishing and Assembly

Vitamins, Equipment, and Finishing
Handy tools:
-Mill file for smoothing parts
-Black permanent marker
-X-acto blade
-1/8-inch drill bit
-Razor scraper
-Super glue
-Bamboo Skewer (or similar) for positioning bits of tape inside the body

-14mm red transparent disc for frame indexing hole (office supply stores usually carry transparent colored portfolios/report binders)
Pinhole, 0.22mm diameter, provides nominal f/135

Gaffer tape, 1-inch wide, used for:
-Covering tripod thread inside camera, 1.5 inches
-"Holga Flap" over frame indexing hole, back of camera, 3 inches
(in the absence of Gaffer tape, any opaque black tape that will adhere to your camera may be used. If you are interested in building more pinhole cameras, a roll of Gaffer tape is a great investment.)

Camera Body

The camera body is assembled with five other parts:
-Hexagonal pinhole plate
-Shutter Key
-Mounting ring
-Top Frame

The body of the camera prints in one piece, with a 1/4-20 tripod mount thread in the bottom of the body. Use a 1/4-20 bolt to gently chase out these threads - DO NOT CROSS THREAD. Inside the camera body, use a short bit of gaffer tape to cover the threaded hole inside the bottom of the body. A bamboo skewer or similar can help with positioning the tape.

The shutter slides up and down in the front of the camera body. The tolerances for this fit are deliberately tight to allow for fine tuning the fit of the shutter in the dovetail. A small file can be used to smooth the inside of the dovetail, and the edges of the shutter can be sanded/filed for a smooth, but sticky fit. There needs to be enough friction to hold the shutter open and closed. The fit will loosen up the first few times it is opened and closed. If the fit is too loose, either gently heat the shutter and bend it into a shallow bow, or print a new shutter blade from the collection of parts.

With a marker, blacken the backside of the pinhole before installing. The pinhole is mounted on the hexagonal plate and sandwiched between the shutter and the camera body. A dab of super glue will hold the pinhole in place during assembly.

The trapezoidal-shaped key fits into the body, holding the shutter captive. With an X-acto knife, trim the supports inside the cavity the key fits into. The fit is tight, and the key can be pressed into place without glue. The key can always be pried out if you ever want to change your pinhole,

The 14 mm disk of transparent red plastic is to be mounted inside the circular depression, in the back of the camera body, sandwiched between the body and the mounting ring. Only the smallest dabs of super glue are required to hold everything in place. Too much glue will fog your plastic. For maximum light proofing, a small flap of gaffer tape can be used to cover the indexing hole on the outside of the body during use.

The top frame is designed to fit into the recesses inside the top of the body, with the arrow pointing to the right (shutter is in front of camera). The convention is to load the film on the LEFT and advance the film on the RIGHT, but with a 6X6 frame, the index numbers are in the center of the film's backing paper and the film can be loaded on either side. If you are a southpaw, or if you just prefer winding on the left, there is a part called top_frame_left that is a mirror image of the top frame, with an arrow pointing to the left.

The top frame is best mounted by inserting at a 45 degree angle, wedging the tabs into the recesses simultaneously and gently pushing downward. The top frame will pop into place.

Camera Cap

The cap plates consist of a cap insert and two cap sliders.

Carefully remove the support from under the cap insert. This surface should be smooth and flush. An X-acto blade can be used to trim everything flush inside the winder cavity.

There is a triangle on the top of the sliders in closed position that indicates the film plane and the horizontal angle of view. When putting the cap on the camera body, orient this framing triangle to point forward.

The printable winders and knobs have holes through them that keep them captive, sandwiching the sliders and the insert together. I use a short length of filament through the holes as a cotter pin. The hexagonal shaft transmits the torque from the knobs, not the cotter pins.

If you prefer the look and feel of instrument knobs, the winders_alt or the set of winders from Shapeways can be used with your knob of choice. You may need to trim the end of the winder shaft for a snug fit. Sanding the bottom surface of your chosen knobs will prevent a rough surface from fretting at the top of the cap.

To mount the cap, pull the sliders apart, center the cap insert in the top of the body, and slide the top closed. A bit of tape can be used as a safety to keep the cap from sliding open.

Loading Film into Camera

You will need an empty spool from a roll of 120 film, or you can 3D print a 120 film spool!
These instructions assume you are loading film on left and winding on the right. Reverse as appropriate.
-To load the camera, open your roll of 120 film.
-Remove the paper tape around the roll of film. Set aside.
-Pull several inches of paper from the spool, taking care to prevent the film unwinding.
-Insert the end of the paper into the empty spool, and turn twice, capturing the free end as the paper wraps.
-Pull the spools a couple more inches apart.
-Again, preventing the film from unwinding, place the film clip loosley around the TAKE UP spool, on the Right side, facing forward.
-Insert the SUPPLY spool (Left side) into the camera, pulling more paper from the spool if needed to get the TAKE UP spool and film clip into the Right side of the camera.
-Gently slide film, spools and film clip into the camera body. It takes a little practice, so take your time. If things get janky, stop, rewind the film and start over.
-When properly inserted, the spools will be flush with the top of the camera body and the paper below the top of the top frame.
-Put the cap on the camera body, being careful not to allow either spool to move much. If desired, stick a portion of the paper tape that wrapped the new roll of film under the cap before sliding closed. This will remind you what film you have loaded.
-Lift the flap of tape on the back, and wind the knob on the rights side to advance the film.
-Looking inside the red window, you will see a series of arrows, possibly circles or starbursts until you see a number "1". Pay attention to the pattern of shapes that precedes the "1" - this pattern will repeat itself for every frame of film.
-If you wind too far and overshoot the number, just use the other knob to rewind the film to the right position.
-It is ALWAYS prudent to double check your frame indexing when making an exposure if your camera has not been shot in a while or if it has been jostled since last shot.

Note on shooting the terraPin ACME

Because this camera has such a shallow "focal length", there is considerable variation in the distance from the pinhole to the film, at the center of the frame and the corners. I have had great results using an f/number calculated from a spot halfway between the center and edge. Technically, the center will be a little over-exposed and the corners under-exposed, and this optical vignetting is a classic pinhole camera effect.

120 film is notorious for unrolling during unloading and such a "fat roll" will cause photo-fogging light leaks and heartache. Included in the parts is a film clip that fits diagonally inside the camera, around the TAKE-UP spool. The clip will be snug around the exposed roll of film when you unload the camera.

Like all the terraPin pinhole cameras, the shutter mech allows for a "digital" shutter - there is a detent into which you can place your finger while opening the shutter. If you need a relatively short exposure, you can use your finger as the shutter without the attendant jostling that sliding the shutter plate may cause. Take your time, and it is an easy technique to master.

It's beyond the scope of this forum to go into detailed instructions regarding pinhole photography, but I refer you to the User's Guide I wrote for the P6*6 3D printed pinhole camera.

Lastly, if you have gotten this far, and still have questions, PLEASE post in the comments section. I look at my Thingiverse feed EVERY DAY, and I am very responsive to user's questions. Your question may help someone else too!

How I Designed This

This was designed almost entirely in Tinkercad, a deceptively simple, but capable online CAD application. The 3D printed 1/4-20 tripod threads were modeled in OpenSCAD, eliminating a piece of non-printed hardware. In testing, the printed threads (PLA) seem to be robust enough for repeated use. The Basket-weave texture is a native Tinkercad BETA shape generator.

More Information


Helpful and interesting links:
Introducing the terraPin ACME!
An encyclopedic article with cross references
A self-described comprehensive pinhole tutorial
The basics from Kodak - a quick and dirty primer
Make your own pinhole
Pinhole Designer - an excellent pinhole design and exposure calculator. The reciprocity failure function is gold. Sadly, Windows only, but runs well under WINE.
Mr. Pinhole - More calculators and more links.
Worldwide Pinhole Photography Day
[Dirkon -A paper pinhole camera](1970's: http://www.pinhole.cz/en/pinholecameras/dirkon_01.html), 2D printed in a Czechoslovakian magazine, in the 1970's: http://www.pinhole.cz/en/pinholecameras/dirkon_01.html

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Another question! In the first picture the camera features what appears to be a clip to hold the cap tightly closed in place, but I can't find it among the thing files. I found a similar thing uploaded to the OSKAR... Is it compatible with the ACME?

Yes! The 6X6 OSKAR and ACME share the same dimensions where that clip fits. It is an optional part, necessary if the sliders on your camera are excessively slide-y. A bit of gaffer tape works quite well, too - and won't get knocked loose in your bag. I have recently worked out a self-clipping slider set. If you haven't printed that part yet, I can modify the ACME sliders so that you won't need a clip. So many projects! Let me know if that would be of interest!

I was planning on printing the cap in a few hours when the body I've modified finished printing, so any improvement would be greatly appreciated, of course! :D

OK! DONE! There is a new source file, called "terraPin_ACME_Better_Cap_Plate.stl" that incorporates a built-in snap clip into the sliding parts. It will fit all ACME 6X6 body variations. Much better than the arched clip or a bit of tape!

Wow, that was FAST!! Thanks a lot, I'll be sure to post pictures when it's done :D

Hi! First of all, congrats on the design! I love it :)

I was just wondering if there is a reason for the tripod mount not being a blind hole so you don't need to put tape on the inside. Wouldn't it be better like that?

Absolutely. I have had that very idea, but I worry that there won't be enough thread for many tripod screws.

In many cameras, I also use a 1/4-20 flanged nut for the tripod thread, which works fantastically. Folks sometimes have a hard time finding the hardware, though. I recently designed a 3D printed replacement for the 1/4-20 flanged nut, which pops right in, and is replaceable if it gets stripped out. I should rework the ACME family of cameras to use this part.

I just made a very rough modification of your design and published it as a remix: https://www.thingiverse.com/thing:2824605

Terrapin ACME with blind tripod thread


I was also wondering how should I put the tape in the hole in the back so I can see the frame numbers but the light doesn't affect the film. I really don't know what you mean by "Holga flap", sorry. Maybe you could post a picture of what you mean by this?

The "Holga Flap" is a bit of gaffer tape that covers the frame index hole. It probably isn't strictly necessary, but light leaks suck. There is a 14 ? mm disk of red(ish) translucent material INSIDE the camera body, recessed in the wall behind the film plane. I 3D print mine from translucent red PLA, but you can use a plastic file folder from an office supply store (like $0.99). Make sure you can read a dollar bill through it.

OK. It makes sense now. I thought that the Holga Flap was meant to be on the inside of the camera and in my head it completely ruined the purpose of having an index hole haha

Thanks for your replies!

what is the 14 mm red disk , what did you use?

Hi mattknapp

120 film is indexed by advancing the film until the next frame number comes into view. The 14mm red disk gets glued into a recess inside the camera for viewing frame numbers. These days, I print disks from a red translucent PLA, but a clear red presentation folder (think Office Max) works too. The red is a traditional color for this little viewing pane. The camera is designed such that stray light from the window probably shouldn't affect your film, and the pane is probably not strictly necessary. I cover the window with a bit of gaffer's tape on the back of the camera, as I often leave a given camera loaded with film for a while and I want to avoid fogging my exposures. HTH! Todd

can this be adapted to 35mm film?


my friend Clint O'Conner has designed an adapter that allows the use of 135 film in cameras that take 120 film.

Of course, you lose the ability to accurately index your frames, and should, in fact, tape the sliding cover for the frame number window in place to avoid ruining your photographs. I get that 135 film might be easier to source and process sometimes, but with the Internet, you can buy film online and send it to remote labs for processing. I promise you that 120 film makes better pinhole than 135, by virtue of the larger frame size.
Hope that helps.

35mm Film on 120 Spool

If there are awards for this kind of thing, you should get at least three!

OMG...stunning! a gift to the world, thank you so much!!!