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  1. #1

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    Jun 2012
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    Polaroid Pack Film Pinhole (my first pinhole, yay!)

    Normally I'm a rather hardcore digital guy, but at school (photography program) I decided to shoot a couple of rolls of 120 on Mamiya 645 and Hasselblad loaners they have, and to get the original workflow experience I also borrowed a Polaroid back for these cameras. Of course on these the polaroid is usually just for getting some instant feedback from the camera and not for actually shooting real photos, especially since the image you get is still the 120 format size of 6x4.5cm or 6x6cm.

    But I thought the polaroids were kind of cool, even in these modern times. I could use it to immediately give models a printed photo of themselves which they kind of liked, and more importantly I could take photos on film, get instant feedback, and I found that with Fujifilm FP-100C I could clear the anti-halation coating off the negative with bleach to get a scannable or enlarger-printable transmissive negative too. To make things even better, there seems to be a bunch of recently expired Fujifilm FP-100C pack film out there for $7-8. (It's still being made, so this is probably just extra stock that didn't get sold from the last production run.) And if I want B&W, they're still making FP-3000B.

    So I bought an old unrestored 1967 Polaroid Automatic 250 Land Camera ($60 on eBay, guess prices have gone up a bit recently as they used to be cheaper) which works nicely after some cleanup and minor modification.

    At some point, after finding out that you can actually get pretty good image quality if you do it right, I thought it would be cool to make a pinhole camera. I got some 4x5 sheet film, but I figured why not just use instant pack film for my first shot at this since I can get instant feedback on how the thing is working?

    The problem with pack film is that you really need some sort of holder for it that has the proper roller assembly needed to evenly spread the developer reagent caustic goop between the film and receiving paper. This doesn't seem terribly easy to make, and if everything isn't precise then you just end up wasting film packs at a time as things jam in ways that are very difficult to recover from.

    So I bought this thing off of eBay for something like $25 plus $20 shipping.

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    (Pack film back removed and covered over with my "shutter".)

    This is a cutting edge Tektronix C-53 oscilloscope camera used to make hard copies of whatever's on an old purely analog oscilloscope's screen. Damn bro, high tech! (These days I'm assuming oscilliscopes are digital and can just print whole signal traces on any sort of printer, but for some reason I think some people are still using the old ones and that my explain why Fuji is still making FP-3000B film. ISO 3000 or higher ISO film is what's really needed for these, and who cares about color.)

    The main thing I wanted here was the pack film back which almost justifies the whole cost of the thing. I'm not sure what I'm going to do with the rest of the camera just yet (it only focuses to the end of the frame though it has an f/1.9-f/16 aperture, nice optical elements, fully manual controls, and "macro" focus none of which you'll find on a regular consumer land camera) but I think I can come up with something. I also got a Polaroid 335 (cheaper, plastic) camera from my neighbor for $20 so I might end up using that as a pinhole though it is a little more of a pain to modify.

    Anyway, tektronix c-53 pack film back:

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    That's the normally open side that attaches to the camera, but I cut out an 8x8cm square of cardboard, spray painted one side black, punched a hole in it, made a pinhole in soda can side aluminum, taped it down to the cardboard, and taped the whole cardboard assembly over the window in the back. Then I took a square of Roscoe Cinefoil (black coated foil used for light modulation and such) and taped it over the thing to use as a shutter. Luckily there are these little bevel things that help act as a light trap, or I might have made it smaller. Really I could probably make it smaller anyway or otherwise come up with something better, but this is OK for now.

    Shutter open:

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    I'd take the thing apart and take macro shots of the pinhole etc but I have some film in it right now and I'm too lazy to remove and bag the pack in a dark area.

    Only problem with it as it is now is that without some sort of "extension tube" for the pinhole, the focal length is only like 40mm:

    Click image for larger version. 

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    That means vignetting, but also a lower f-number (based on the mr. pinhole wizard) that makes it a little more convenient to play with. Luckily I can remove that plastic frame inside the front of it (enlarging the 8x8cm square) which means I should be able to later elongate it as much as I want. The pinhole I made is kind of crappy anyway and I'm going to replace that regardless. (I used something like the sewing needle and pin vice method but I filed down a wire, or tried to, and used an x-acto knife handle as a pin vice. Even sanding off burrs it's still pretty bad, though I think I actually came respectably close to 0.25-0.3mm.)

    This thing is of course a pain to use with no tripod or stand of some sort so....

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    I'm going to take that brass light stand stud that I never use, drill a hole in the bottom of the film back, and bolt it to the bottom. That'll give me a standard 1/4-20 tripod hole and reasonable stability if I use some large washers.

    Out of 6 test shots taken from my balcony, these were my best photos. (6-8 seconds in bright daylight).

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    Due to the reciprocity failure issue, I'm supposed to use a +7.5Y and +12.5R filter for color correction, but all I have right now are +15Y and +30R Roscoe Calcolor filters that are made to go over lights, not use as shoot throughs. The photo on the left is with my overdone filtration, and the one on the right is unfiltered showing the cyan cast that you're supposed to be correcting for. I think I had to add something like at least +2 stops due to the reciprocity failure. (This instant stuff has a pretty high contrast tone curve, and that makes the reciprocity issues worse on the extremes.)

    The dark lower area in each photo is due to a shadow on the ground (sun is behind the camera blocked by the building that it's looking out of) which gets exaggerated by the range and tone curve of the film. (it stupidly took me about 3-4 shots before I realized that it was a shadow and not something blocking the exposure somehow.)

    So not too bad, but I kind of doubt that even the latest tech pack film is going to work that great for pinhole style long exposures like this. At least I can use it to test out newly drilled pinholes and still create 3.25 x 4.25" or larger images on 4x5 sheet film taped into an empty pack film cartridge. Maybe I can even find some way to use old pack film cartridges as darkslide-capable film holders.

    So the next steps are to bolt on the tripod mount, create an extension box/tube to get the focal length to 1.40mm, drill a much nicer 0.5mm pinhole, and create some sort of crude viewfinder.

    Comments?

  2. #2

    Join Date
    Jun 2012
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    Ann Arbor, MI, USA
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    Here's one of the photos after scanning (in my document scanner, which wasn't made for photos, thus the streaks and artifacts) and improving the color balance in Photoshop. (Not terribly proud of it but I figured that I should at least upload a photo that was scanned rather than taken with a camera with glare/reflections.)

    Something like a 6-8sec exposure at f/150 or so.Click image for larger version. 

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    Last edited by aterimagery; 07-05-2012 at 01:59 AM. Click to view previous post history.

  3. #3
    ced
    ced is offline

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    Oct 2011
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    I think it is very nice, maybe the pinhole you are going to make may give slightly sharper results.



 

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