View Full Version : Polaroid SX-70 Optical Technology for LF Film?

Frank Petronio
30-Apr-2006, 19:37
Looking over my crusty old Polaroid SX-70s and 600s got me wondering... Here are compact cameras that manage to deliver a fairly large image onto a large area of film (3x3 inches or so?). Now granted, I understand that in terms of optical perfection they must fall short of a traditional straight optical paths. But wouldn't it be sweet to rip out the Polaroid film mechanism and mount a Graflock back to a compact folding Polaroid body? Has anyone ever done this?

Also wondering if the folding optical path is an original Polaroid design or if someone in Dresden invented it 1909?

Or did Noah Schwartz invent it, Wm Littmann patent it, and Dean Jones figure out how to make it cheaper?

Mark Sampson
1-May-2006, 17:53
The Sx-70 lens is f/11, I think. And I think the low resolution of the print material would have covered a multitude of optical sins. It would be easier to do with a 180/195, even as flexi-flyer as they are.

Donald Qualls
1-May-2006, 21:23
Actually, the SX-70 has f/8.8, and the lens is a good quality triplet or Tessar type (counting reflections in my Model 2 seems to show four elements). They didn't make it faster because there was an expectation you'd use flash in low light (and the camera, if steadied carefully, would make perfectly fine images in a well lit living room, even in the earlier models; later ones had longer time exposure capability), as well as putting a lower bound on depth of field -- important for a consumer camera, I'd guess. I expect putting actual film at the focal plane would result in a negative capable of considerable enlargement.

However, you'd have to both supply 6V and fool the camera's electronics into thinking it had a film pack loaded with film remaining (since those electronics handle the SLR activities -- close shutter, flip mirror, open shutter for correct time/aperture, calculated on the fly, close shutter, return mirror, eject film for processing) -- and you'd have to maintain the correct film plane (no diopters, because those would completely bollix up the SLR focusing).

Given where the film plane falls in these cameras, I doubt you could manage the last trick with conventional large format accessories (the others aren't all that hard), though I seem to recall seeing an SX-70 family camera converted for 3x3 pack film; the peel-apart packs have similar construction to the front plate of the SX-70 pack, so wouldn't be too hard to install and maintain film plane. If only you could still get Type 85...

One thing that seems at least remotely possible would be to put film into an original pack, sheathed to similar thickness and stiffness as the original prints, and mount a dark bag on the front of the camera to catch the sheets as they eject (though doing this and keeping the folding capability might be Too Much Fun -- best bet to my eye would be to reroute the ejection through the bottom plate instead of out the front where prints eject in the stock configuration). It's possible to replace the batteries in SX-70 packs, too (presumably with new ones from 600 films, since you can't buy PolaPulse batteries loose any more AFAIK), or you could mount an external battery pack and feed power to the internal contacts through the same slot that ejects your exposed film, or simply bypass those contacts with through-the-case wiring.

Hmm.... Now I wish my Model 2 were in better condition; this is starting to sound possible...

2-May-2006, 00:44
Greetings all......

the question was posed......
<<Also wondering if the folding optical path is an original Polaroid design or if someone in Dresden invented it 1909? >>

To answer the question as to if the SX-70 optical design was an in house polaroid or not? I can answer...... The optical design of the SX-70 was designed by my father-in-law Richard Weeks.... He ran the optical dept for Polaroid from the early 60's till his retirement in the late 80's....

Also... a few years ago I asked him about wiring an external battery to the SX-70 and replacing the filmpack with a 6X9cm Grafmatic film holder....... Well I can still hear his laughter today...smile....so take what you will from that......

Oh I'm going to forward this thread to him for his thoughts......


Frank Petronio
2-May-2006, 06:12
Thanks for clearing that up. That Issac Newton fella was a lousy photographer IMHO.

Donald Qualls
2-May-2006, 19:39

I got to looking at my Model 2 last night, and at a couple empty film packs. I found that, with use of a dark slide from a 600 pack, I was able to work the film pressure spring and battery out of the pack through the print ejection slot, and then back in as well.

However, what really interested me, was the realization that I could make a replaceable-battery single-frame film holder, with dark slide, that would replace the inner bits of that pack. It would require removing the glued-on front edge of the pack, trimming bumps if needed to ensure the pack will seat in the correct camera, and building an insert that fits in the pack and carries four AAA cells (plenty of room inside the pack shell), along with a film sheath, pressure plate, velvet light trap, and a ramp to guide a dark slide over the sheath to prevent scratching film. It would also require recutting film, of course, but it's very much within the possible to shoot relatively ordinary sheet film in an unmodified SX-70, 600, or Spectra camera (a neutral density over the meter would increase exposure on the 600 and Spectra family cameras to use film slower than ISO 640).

Now all I need is a cheap source of spend SX-70 or 600 film packs to convert... ;)

Frank Petronio
2-May-2006, 20:17
So it would be a one shot then into the darkroom type of deal?

Come on, where is that HUW Finney guy? He put a light meter into a Leica IIIc - surely he can crack this case!

All you engineers - maybe we should offer a prize like they were doing for the private space launches?

Donald Qualls
3-May-2006, 11:53
So it would be a one shot then into the darkroom type of deal?

No, not at all -- more like a one-side film holder; as many holders as you're willing/able to carry, that's how many exposures you'd get. The dark slide would be pulled when the modified film pack is fully inserted, before closing the camera's loading door, then after exposure the loading door would be opened and dark slide reinserted and the pack removed (hence the ramps to guide the DS over the film, while letting the film position properly against the inside of the pack for correct focus).

I need to find a local dealer of hobby size black ABS sheet (.010", .020", and .040" thicknesses should do it), though failing that plain white polystyrene and some black enamel would probably cover the territory; I've got two packs I can work on immediately, one more in a camera and one in reserve with the original 600 film still in. That's plenty for proof of concept. The hardest part, from where I sit, will be accurately cutting the film in the dark.

Hmmm. Another option exists for the really adventurous -- one might be able to repackage 3x3 peel-apart Polaroid films into the SX-70 type pack. Don't know I want to go there, though; designing the interior of the pack would be a lot less simple.

Frank Petronio
3-May-2006, 13:16
Like the various pinholes, the Hobo, and the Lens Baby for digital SLRs, there is probably a large market of people like me who would spend $2-300 on a "second" novel camera like a hot-rod Polaroid SX70. I think the key factor is the price point being low for the value of making some different and interesting images.

I suspect many large format photographers are already a good aidience because they have been so conditioned to pay hundreds for simple accessories (some of us at least) that a couple of hundred bucks doesn't scare us away. Unlike, say, a normal sane person.

So get busy Don! I hope you can really do it and post the process/results. Take some snaps of how you build it please!

Frank Petronio
3-May-2006, 23:33
My friend summed it up: "...a flat camera like an sx-70 with a Grafmatic on the bottom. Whoa, that would rock..."

Donald Qualls
4-May-2006, 09:04
Too many construction projects on my plate already (working on building a matched pair of flat film, hyperwide 6x24 on 120 pinhole cameras, for instance, and never seem to get anywhere with that build), so this won't be immediate, but it's now quite high on my list. I took the glued-on front plate(s) off a film pack last night, and I'm now certain the conversion can be done -- and, of course, I have a working SX-70 to test in. Just need time and materials to actually do it.

And of course I'll document the process -- I've got lots of web space with stuff I haven't worked on in literally years (lathe building, model rockets, etc.) that I've been thinking about clearing out, to be replaced with photographic construction documentaries and gallery storage...