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View Full Version : polaroid propack camera lens ?



cmorganf64
12-07-2005, 10:52 AM
Hey guys.

Im looking to convert a polaroid propack camera to a pinhole...but...

Id first like to see if I can simply create a really wide angle effect with the camera, using the lens, not a pinhole yet.

Ive inverted the outer lens to allow for a much wider look, but the inner lens will not allow me to re-attach the outer lens...the outer lens convex shape touches the inner lens.

Is the inner lens a neccessary lens? Is the purpose of that inner lens to reduce the image projected to the film plane size only, or is there another purpose?

Id like to see what I can do with this camera before I do a complete pinhole conversion. Id like to get a really wide angle effect....the same reason Im heading toward the pinhole effect.

Any suggestions are appreciated.

Chris M

ImageMaker
12-07-2005, 04:34 PM
It depends on what lens you have on that camera. If it's the two-element plastic lens, you need both pieces to get the original focal length; each element separately will have roughly twice that focal length (and lots of aberrations).

If it's one of the three-element lenses (likely the case with a ProPack), you might be able to get a focus at a shorter distance (possibly around 70-75 mm instead of 114 mm) using only the rearmost element (the one behind the shutter); most triplets are designed so the front two elements are mildly negative and the rear element is a strong positive. You could also get an extremely short focus with only the front and rear elements (both positive lenses) and without the middle one. You won't get very wide coverage angle with those combinations, but it might give interesting effects -- there'll be both chromatic and spheric aberration, and with the doublet configuration possibly some vignetting from the front element's mount. You'll also have to mess with the exposure system, because the lens will be faster with the same aperture on a shorter focus.

The simplest way to get a wide angle lens effect without big aberrations with that shutter and lens board would be to cobble on a shorter focal length lens from another camera; a 105 mm from a 6x9 cm camera will almost cover the 3x4 format of the Polaroid, while an 80 mm from a 6x6 will give very distinct vignetting. Neither one will look extremely wide compared to the original 114 mm, however; for that, you'd need something along the lines of a large format wide-angle lens like a 75 mm Angulon or even a shorter lens than that.

All of the above will require resetting the focus on the Polaroid, which is a non-trivial task; the whole camera is designed around that one focal length, and on the folding Polaroid I converted, there wasn't any way to adjust the focus even to bring the original lens back into focus (I presume the camera was damaged in some fashion before I received it; perhaps dropped when open or forced closed without unlatching the scissor arms).