Why You Can’t Do Double Exposures with the Polaroid SX-70
(But you can with other Polaroid cameras)
What are double exposures?
These are double exposures:
You see two images overlapping. The film exposes twice. If you see more than two images overlapping, it’s called multiple exposures. The method is the same, you just expose the film multiple times.
What happens in a Polaroid OneStep when you do double exposures
The Polaroid OneStep has the double exposure function. This is what happens in the camera when you use this function:
| At this point you can see through the viewfinder. | |
| First exposure | |
| ✓ | Step 1) Shutter opens |
| ✓ | Step 2) Light enters, film gets exposed |
| ✓ | Step 3) Shutter closes, film does not eject |
| Second exposure | |
| ✓ | Step 4) Shutter opens again |
| ✓ | Step 5) Light enters, film gets exposed again |
| ✓ | Step 6) Shutter closes, film ejects |
Note that you can see through the viewfinder for the whole time. It works.
A normal single exposure with the SX-70
Before we go into SX-70 double exposure, let’s try to understand how a normal exposure works. This is what happens in an SX-70 right after the moment you press the shutter button.
| At this point you can see through the viewfinder. | |
| A normal single exposure | |
| ✘ | Step 1) Shutter closes, mirror flips up |
| ✘ | Step 2) Shutter opens |
| ✘ | Step 3) Light enters, film gets exposed |
| ✘ | Step 4) Shutter closes |
| ✓ | Step 5) Mirror flips down, film ejects, shutter opens |
As you can see, it’s more complicated than the OneStep. It’s because the Polaroid SX-70 is an SLR (single-lens reflex) camera, and SLRs require a mirror. Did you notice that the viewfinder turns dark when you take a photo?
Please pardon my sloppy photoshop skills. If you’re really interested, here’s a very nice video demonstration: https://youtu.be/Lo_1pyQ7xvc?t=204
The problem with double exposures on the SX-70
In layman terms, when you’re shooting the second exposure, the viewfinder is still dark and the camera is stuck in the open position. You’ll be guessing the framing and focus, which is totally impractical!
This is an imaginary example of what will happen if someone adds the double exposure function to the SX-70.
| At this point you can see through the viewfinder. | |
| First exposure | |
| ✘ | Step 1) Shutter closes, mirror flips up |
| ✘ | Step 2) Shutter opens |
| ✘ | Step 3) Light enters, film gets exposed |
| ✘ | Step 4) Shutter closes, mirror stays up, film does not eject |
| Second exposure | |
| ✘ | Step 5) Shutter opens again |
| ✘ | Step 6) Light enters, film gets exposed again |
| ✘ | Step 7) Shutter closes |
| ✓ | Step 8) Mirror flips down, film ejects, shutter opens |
Note that from steps 1 to 7, the viewfinder is blocked and you can’t see through.
But wait, I don’t get it. Some SLR cameras have the multiple exposure function, how come it’s possible?
Polaroid did not add the multiple exposure function to the SX-70. The mirror is connected directly to the gears that drive the film ejection mechanism. So when the mirror goes down, the pick arm and rollers move with it.
For other SLRs, this is not the case. Therefore, it is possible to add the double or multiple exposure function to SLR cameras, just not the SX-70.
There are workarounds, if you insist.
Here are two ways to do double (or multiple) exposures in a Polaroid SX-70 if you positively absolutely have to. I won’t go into too much detail since this is already a very long post.
1) The “transparent film” method
This method requires a bit of technique. After you make a transparent film the same size and thickness as ordinary film, insert it on top of the deck of unexposed film, in the dark. When the shutter opens, the light will pass through the transparent film and expose the film underneath, but only the transparent film will be ejected. It’s complicated, don’t worry if you didn’t get it.
2) The “stop the pick arm” method
People have tried various methods to stop the pick arm from hooking the film after the first film exposure. But these methods are intrusive and you risk breaking your camera. Not recommended.
Conclusion and comments
To conclude, it is possible to do multiple exposures with the SX-70, but every method is impractical and inconvenient. So far there doesn’t seem to be a good solution, perhaps I have overlooked something.
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