Saturday, April 19, 2008

OM digial back

I've been wanting to play with the idea of a digital conversion for old manual SLRs for a while. I don't know if it's a practical proposition but it's a fun project. The biggest difficulty will probably be getting and interfacing a large enough CCD.

As a first step I'm been playing with cheap Labtec webcams. I bought a bunch of these for something like 3 quid each for ebuyer. They are only 320x240 and 25fps but they'll do for a proof of concept. They also have good Linux support which is a plus.

Here's an image from the webcam:

I'm only interested in the CCD, not the optics so I strip them down:

and wrap them in a bunch of insulating tape so nothing shorts out:

OK, now we need to mod the OM itself. I'm using an OM2 here, it doesn't really matter which OM you use, for our purposes it's really just a mount for the lens. So to start with we need to jam the shutter open. OM cameras have "B" mode. This keeps the shutter open as long as the trigger is depressed. To constantly depress the trigger without hacking the camera I put a screw in the trigger and used a bunch of cable ties to pull it down.

Next mod the camera back.

Remove the back, and the sprung plate that lies against the film.

Next I drilled out the back. I used my Dremmel. Dremmels're really cool for this kind of thing. I used the piller attachment, they call it the "workstation":

When your cutting out a hole of the CCD you better use those goggles!

Final cut out back should look something like this (but better):

Now put it all together:

That's it! It works ok, obviously because the CCD is so small compared to 35mm film you end up imaging only a small part of the full frame. It basically looks like it's zoomed in all the time. Here's an example image:

Next up I'll try a better CCD. I've bought a Phillips SPC900NC for this purpose, it's a really nice webcam (1.3Mega pixel, and says it can do 60fps). The images look really nice...

Ideally I'd like to interface all this to a embedded processor like a gumstix, so rather than being tethered to a PC it's more like a real digital camera.

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