Instant Camera modification - help wanted

(Gilbert Townshend) #1

So as some of you may know I’m really interested in film photography and shoot a lot of pictures. A couple of years ago the last producer of peel-apart instant film (Fuji) stopped producing it and as a result the camera I most liked shooting it on suddenly had no way to do so any more. Now my hasselblad is still perfectly capable of shooting film but there’s just something lovely about being able to see a shot you just took.

So as a result I tried buying one of Fuji’s still made integral (think old square Polaroid but a different size) cameras. While the film is lovely they cameras are not, they’re cheap and plastic and have plastic lenses that you can’t focus.

My current plan is therefore has been to modify a camera to shoot this still produced and relatively cheap instax film via the lenses on my hasselblad. The good thing about this and other medium format cameras is that they have removable film backs, as shown below:

The square one is for traditional film and the larger rectangular one is for the now extinct fp100-c instant film.

I have bought via eBay a few knackered (well, admittedly one I knackered) plastic instax cameras that look like this:

My plan is to salvage the film holding and eject mechanism from one of these cameras and mount them to the connecting plate from an existing film back.

So far I have disassembled one camera and one plate and I think they should roughly fit, with the next step being to remove as much material as I can to get the film plane as close to where it should be as possible.

However, I’m now in need of some help. I don’t know much about bonding these things, I doubtless won’t be able to use all of the existing screws, plus in removing the lens I’m going to end up trashing the electronics involved. I don’t need most of it, given it will no longer have to meter or move the lens but I do still need to be able to trigger the eject and run the motor. I’m not sure how to do this.

I also scared myself shitless trying to discharge that massive flash capacitor the first time I poked at it.

I also probably need some help with aligning the film plane and possibly making some plastic parts to make it as light right as possible.

So uh, anyone around for electronics night who might be able to advise?

(Alexander Baxevanis) #2

You may get some more details from other people who’ve done this:

I want to do the same on my Bronica so would be happy to meet up and help, but not sure when - maybe sometime on Sunday 9th?

(Gilbert Townshend) #3

Sadly I’m at work in the market on Sunday but I could do a weeknight, it would be awesome to have someone else involved! Which bronica is it?

I’ve seen that link before but I’ve been mulling this thing for probably over a year. They’re rather light on details and removed the eject motor, I’m really aiming to keep it in mine. They also used an instax mini, the logical choose would be the relatively new square format that is almost exactly the same size at a 6x6 back (I think it’s 58mm) but they’re still kind of expensive to be possibly destroying.

The part I am least confident about it the electronics, I’m sure a timer to switch on a motor isn’t that hard, I’m just afraid of frying things because I know that chip logic is a different voltage and motors can be funny with initial power draw and slowing down.

(Alexander Baxevanis) #4

This week is a bit crazy due to xmas parties/shopping/family stuff, but maybe we can do some evening fro the 18th onwards.

Re: keeping the motor, you can see how it’s wired in one of the cameras here.

The electronics of the motor aren’t going to be too challenging, you could easily wire it up to some sort of timing circuit.

The specs for the motor in the above photo are here:

You can see it draws around 83mA @ 3V, and it’s got gearing attached to which reduces the speed and increases torque.

BUT … I’m not 100% convinced that it’s worth keeping the motor, given the extra space that the motor and the batteries will take, and the additional mechanical fitting challenge.

(Gilbert Townshend) #5

That’s one reason why I went for Instax wide, with the shape of it the batteries and motor fit out to one side and don’t really interfere with the back. Rather amazingly it seems to line up, at least sideways, almost perfectly. The hardest part I think is going to be getting it thin enough to align with the film plain and with enough mechanical stability to bolt on to the mounting plate.

When I was probing it last week the motor in mine seemed to be running on 6v and I didn’t desolder it to measure current draw. I know very little about designing electronics so while I’m sure a timer would be simple I really need some advice about how to put something like that together.

(Alexander Baxevanis) #6

Ah, I didn’t notice you were working with the Instax wide!

To make a timer for the motor, you can probably just use the usual 555 timer circuit:

Because the 555 chip has limited current output, you’ll need to add an extra transistor to switch the current between the battery and the motor.

(ignore the Arduino bits, as you’ll be driving the transistor from the 555 chip)

We probably have all these components in the space, so it should be easy to prototype.

I have Tuesday and Friday off next week, so happy to meet you at some point if you can also make it?

(Gilbert Townshend) #7

Sure, either. I’ll be there on Tuesday anyway I think. This was pretty much what I expected, all that might be hard now is the actual machining.

I’ll tey and read through those links at work tomorrow.

Help is very much appreciated and I’m excited that this might actually finally get made.