Polaroid 340M - Manual Shutter Speed Conversion

[zzpza]

So, in my pursuit of making the Polaroid folding land cameras from the 60's and 70's into an everyday usable camera, I had to address the metering system.

Previously I had converted the camera to use modern AAA batteries and currently available Fuji FP-100C, FP-3000B film (see here).

But this still meant I was at the mercy of the horrible metering system. There was only one solution in my mind (beyond swapping the lens and shutter, which is very expensive) and that was to replace the electronics controlling the shutter.

After a bit of research I found someone who had the same idea and placed all their project info in the public domain. This was a good place to start using their design as a pilot to see how the camera would handle.

After collecting the necessary parts to build the new electronics, I tried it out on the shutter from a Polaroid 320.

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Testbed by zzpza, on Flickr

With the electronic design working, I transferred it to stripboard, took my old Polaroid 340 apart and connected it all up.

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Measure Twice... by zzpza, on Flickr

The LDR ("Electric Eye") and all the old analogue electronics have been removed. The window used by the LDR is now where the shutter speed selection dial is located.

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Lens Board Modification by zzpza, on Flickr

The shutter currently has a range of bulb, 1s to 1/256th.

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Prototype One by zzpza, on Flickr

In it's current state there are a few areas that I can make some improvements, but all in all it's now a pretty fun, easy to use and - most importantly - predictable camera.

Here's a photo from the first film pack I ran through the camera.

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Polaroid 340M 00003 Genesis by zzpza, on Flickr

 

[Robert Lai]

The old electronics used to provide extended shutter speeds such as 10 seconds. Couldn't you provide yourself with such extended speeds?

The main problem with the "electric eye" systems is that they encompass the entire field of the lens, and any highlights cause severe underexposure. Could you have made an "exposure memory lock" circuit instead?

 

[zzpza]

The old electronics used to provide extended shutter speeds such as 10 seconds. Couldn't you provide yourself with such extended speeds?

Bulb gives me any length shutter speed that I can time myself. 10 seconds, 30 seconds, 4 minutes, you name it.

Having said that, one of the areas I am planning to improve is the handling of multi second speeds (I like night photography) and also to increase the speed of the micro controller to get a faster maximum shutter speed.

The main problem with the "electric eye" systems is that they encompass the entire field of the lens, and any highlights cause severe underexposure. Could you have made an "exposure memory lock" circuit instead?

This would be perfectly possible, but it's just another patch or work around for a broken system. i.e. this would address the symptom, not the cause. I would rather use a quality hand held light meter and then set the camera. Job done.

 

[shadowfox]

A hearty "Congratulations!"

What a well done and useful conversion.

 

[Dante_Stella]

Cool - do you by chance know the where the master exposure control is on the old electronics? I have a 450 that seems to be underexposing, but the autoexposure seems to react to different levels of light (including super-long exposures). I have no fear of soldering irons, but I don't remember seeing anything that looked adjustable.

Thanks
Dante

 

[zzpza]

do you by chance know the where the master exposure control is on the old electronics?

The 340 I took apart (which seems to be a later design) had two variable resisters which I assume to be the meter adjustment - one for indoor using 3200 ASA and the other for all other speeds. The 350 I took apart didn't have any adjustment in it.

If there's no adjustment you can find, I would place a transparent sweetie wrapper over the LDR. Yellow should be good for around about 1 stop. Either that or make the same conversion I have. 🙂

 

[pdexposures]

This is awesome, but way above my skill level.

There is however a man in Seattle, WA who owns a store called Rare Medium. He is working on an attachment to the camera (won't require any modification and can be removed just as easily as it goes on) that will allow you to select your shutter speed manually.

 

[zzpza]

Interesting. My guess is that it is a controllable light source with calibrated settings for the different shutter speeds.

Either way, it seems a bit convoluted to get a manual shutter speed 100 series land camera. However I can appreciate the desire to not permanently modify a rare or prized camera. For me, the automatic land camera doesn't fall into that category, hence my mod. 🙂


Polaroid 340M 00013 Genesis by zzpza, on Flickr

I'm really getting to like this camera... 🙂

 

[zzpza]

Also, many thanks to everyone for the compliments - it is appreciated! 🙂