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terraPinstax Wide Pinhole Camera Body

by schlem, published

terraPinstax Wide Pinhole Camera Body by schlem Jul 10, 2017

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Summary

This project came to life when a friend requested that I design a pinhole camera body around an instant film back, made by Lomography for the Belair Lomo camera. She wanted a wide angle of view, but otherwise gave me free rein. I settled on a 35mm "focal length", and after some math worked out that the aperture should be 0.26 mm in diameter. This gives a F Stop of f/136 in the middle, but shooting this at f/165 is a nice compromise between an overexposed center or dark, dark corners.

The Lomography instant film back (User's Guide) uses Fujifilm Instax Wide film packs, a popular and vibrant instant film stock. The film is available in a variety of formats, and a variety of cameras are available from Fujifilm and other manufacturers. Unlike Fujifilm/Fujichrome professional film stocks, technical data is not provided for reciprocity failure (RF) behavior. I am testing the film with the goal of a reliable RF curve, but I am still in the early stages. Experimentation continues.

Previously, I designed a pinhole camera body to work with the Lomography Instax Mini film back for the Diana F+ camera. I wrote a bit about my struggles getting the film to work in a pinhole camera on [Hackaday}(https://hackaday.io/project/211-pinstax-3d-printed-instant-pinhole-camera).

Film specifications (wikipedia)
Film speed ISO 800/30°
Colour temperature Daylight type (5500K)
Resolving power 10 lines/mm
Photos per pack 10
Film size
(W×H) 108 mm × 86 mm (4.3 in × 3.4 in)
Image size
(W×H) 99 mm × 62 mm (3.9 in × 2.4 in)
Aspect ratio 1.618:1
Film pack size
(W×H×D) 115 mm × 92 mm × 20 mm (4.5 in × 3.6 in × 0.8 in)

The film is fast (ISO 800), but my testing reveals that exposures compensated for RF are much longer than many slower film stocks. Shooting the film outside the designed exposure parameters (i.e. slow pinhole shots) also causes a blue color shift. Embrace this, play with this. Colored filters may be able to correct for this, but don't expect accurate color rendering.


ATTENTION
This work is licensed under the Creative Commons - Attribution - Non-Commercial license. This license applies only to the files and documents available for download from the Thing Files section of this Thing.
All other related content (photographs, videos, and verbiage such as contained in "Description" or "Instructions" ) are excluded from this license, with all rights reserved, unless specifically available for download This notice constitutes a clarification, not a change, to licensing for this design.

Print Settings

Printer Brand:

LulzBot

Printer:

TAZ 4

Rafts:

Doesn't Matter

Supports:

No

Resolution:

0.20 mm / layer

Infill:

50%+ for strength and opacity


Notes:

First and foremost, USE OPAQUE FILAMENT. ABS is fine, but PLA is prone to translucence. If unsure, use this OPACITY TOOL to assess the opacity of your filament. I maintain a list of tested PLA filaments and their opacity on that Thing page; If you find another opaque PLA, please share in the comments.

I am currently having great results with eSun Pro Black PLA.

Post-Printing

Clean-Up

BODY:
Hot off the print bed (OK, wait for it to cool, so it doesn't warp), you may have fine strings inside the camera body which will be visible in your photographs. You can pluck these out with tweezers, trim them with a blade, or use a wire brush. These are all methods I have used with success. However, I have been using propane to eradicate any stray strands inside my camera bodies (or on a plate of parts) for several years, and works fantastically.

I fill the space with propane from a source like a lighter or a plumbers's torch - NOT LIT! Propane is heavier than air and will displace most of the air in the camera body. Working quickly, MOVE THE TORCH AWAY and, with a lighter, ignite the propane inside the camera body. The propane will burn quickly and any strands will be consumed or melted into tiny balls. I typically do this several times, and have acquired a reliable technique. A sufficiently-thick 3D printed part will not get hot enough to soften or warp, but I still allow it to cool before handling. If necessary, any residue can be removed with a small wire brush, or even your finger.

DISCLAIMER: Your mileage may vary. Propane is dangerous. I AM NOT telling you to do this; I am telling you what I do. If you burn down your house, it's not my fault. If you burn yourself, it's not my fault. If you ruin your 3D printed object, it's not my fault. I could go on, but any bad stuff that happens because you follow these instructions is not my fault. Be safe.

Moving on, if you print on painter's tape (wonderful stuff), you may have tiny ridges, from the tape seams, on the bottom surface of your parts. I use a razor scraper to shave these off. A sharp razor will take these off nicely. Again, razors are dangerous. See disclaimer, above.

Bore out the shutter bolt hole with a 3mm or 1/8 inch drill bit. Also clear out the holes for the fixing bolts at each end of the body with the same drill bit.

SHUTTER:
The shutter prints upside down, and the top surface will rotate against the camera body when opening and closing the shutter. This surface must be flat for smooth shutter action. I use a coarse mill file to take off any surface irregularities, being careful not to damage the nub that indexes the angular position of the open shutter. Also, the countersink for the shutter bolt may need to be cleaned / reamed for smooth shutter operation. I use a handheld countersink bit for this. It's worth mentioning that metric fasteners meant for countersunk applications have a 90° chamfer angle, but the angle may vary for other fasteners (and by extension, countersink bits)

Depending on how well your printer handles overhangs, there may be other areas that need some finishing before assembly.

PLA can be kind of shiny, so I typically apply a flat black paint to inside surfaces that may cause reflections and ghosting. After assembly, I paint the shutter nut and bold inside the camera body with flat black paint also. It's probably not necessary.

Assembly

You will need the following hardware:

1 - 0.26mm pinhole (making a pinhole is not difficult, but it warrants practice. THIS is how I do it.)

1 - M3 countersunk (phillips or socket) bolt, 10mm length (shutter)
1 - M3 locknut (shutter)
1 - M3 washer (shutter - optional)
2 - M3 socket head bolt, 16mm length (body fixing bolt)
2 - M3 nuts (for fixing bolts, inserted into nut traps in mounting dogs)

Cyanoacrylate or Super glue

Sharpie or similar
Gaffer or Electrical tape

Refer to the CAD renders that illustrate assembly
PINHOLE:
Examine your pinhole; determine which side you want visible from outside the camera. Blacken the BACK of the pinhole (probably unnecessary). I use a Sharpie. Make sure you don't fill the hole with ink, and clean any ink from the FRONT side of the pinhole with a swipe of rubbing alcohol. I cut a small diamond from the tape and carefully center the (BACK side of the) pinhole in the cutout. Again, carefully, I center the (FRONT side of the) pinhole in the opening in the camera body, FROM THE INSIDE. I design my cameras with a little wiggle room here, but if your pinhole is too far off-center, you risk having the edges of the opening and/or shutter blocking light to your film. Go slowly, take your time. People will want to see the pinhole when you show off your camera and you want it centered nicely.

SHUTTER:
The shutter disc is held onto the camera body with the 10mm-long M3 countersunk bolt, fastened with the locknut and washer. It mounts with the countersink on the outside, with the nub inserted into the arced trough in the face of the camera. Adjust the tightness of the bolt to allow for smooth rotation. If it binds at all, something's catching - disassemble and correct. Play with the shutter a bit more - it may become a bit looser. Tighten if necessary.

When you're satisfied with the shutter, the round baffle is glued on the face of the camera. This part not only looks super-cool, but, more importantly, it prevents light from worming its way under the shutter disc and slowly fogging your film. Apply a THIN bead of super glue on the back (bottom) side of the baffle. You don't want to get any glue on your shutter disc. I use a bamboo skewer to prevent big, ugly blops of glue. Gently lower the baffle onto the camera face, around and outside the shutter disc. There is a tiny bit of play in the fit, and, if you work quickly, you can position the baffle to be perfectly centered before the glue begins to set. Clamp with your fingers until you are positive it won't move accidentally.

MOUNTING THE CAMERA TO THE FILM BACK:
The film back was designed for a snap-fit onto the body of the Lomography Belair camera, and has a pair of recesses on each side for a sliding lock mechanism. The dogs (arched pieces with feet) fit into these recesses; they will only fit one way and are identical. The camera body slides over the dogs and is fastened with the 16mm-long M3 socket head bolts. The dogs have a trap that fits an M3 nut. The best way I have found to mount the camera body to the film back is as follows:

  1. Insert the dogs into the recesses at the outside edge of the film back.
    2 Slide the camera body OVER the dogs, into the slot at each end of the body.
  2. STOP when the nut trap is just below the outside edge of the camera body on each side
  3. Insert an M3 nut into the nut trap and slide body several mm over the nut to hold it captive. The nut will fit into a space in the slot. Do one side, then the other.
  4. Fully seat the body onto the film back with the dogs and nuts in place.
  5. Insert the M3 16mm socket nuts into the holes on the edge of the camera body and tighten firmly. Do not overtighten - you could damage the 3D printed parts or the film back!

Read the User's Guide and load film back.

Shoot some pinhole photographs!

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Out of curiosity, what do you attribute the vast improvement in image quality to between this model and the original Pinstax model? Is it just the back, the larger film, or are there adjustments that can be made to the Pinstax model that would get similar results?

I don't know if the different films have different chemistry, but I think there is a light leak in the original design that destroys photos. I have it on my list to rework the mini version similar to the wide and do some testing. Other than being an instant film, I wouldn't endorse this instant film for pinhole, the color shifts irk me.

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