Sunday, July 26, 2009

Multi infinity stop and distance scale

I want to turn Polaroid 11oB into Byron, a camera with lens exchanging capability, but 110B was designed to use one fixed lens, meaning it was equipped with one infinity stop only, and since the strut that keeps front stand in right angled was design movable ( when flat bed folded), but need it fixed in position when front stand stop at infinity, this is another challenge for more than one lens.

original design combined infinity stop and strut fixed functions beautifully in one piece of metal plate, but if I want to mount other lenses than 127mm, I had to create other stops for them, and keep strut fixed.

You see that metal plate for infinity stop and strut fixed, was two screws on oval holes, leaving spaces to fine tune the infinity stop, when satisfied, dead-set with two rivets in front of the plate, to keep it in place while camera through out its life of service.

Now concludes the challenge I faced here:

1. Multi-infinity stop requirement.
2. Strut fixed to keep front stand right angled, moved when folded.
3. Ensure the infinity stops dead-sitting in their positions for long round.

If I can't solve these challenges, it will be meaningless for lens exchanging capability.

The solutions?

Lucky, I made it.

Image above shows the strut fixer, there were a pair of support, with a round knob in front, which can turn around, to allow/keep the stent moved, by turning the knob. And the pair of supports have another important function-- to enhance front stand parallel to the focal plane, keep it from swing.

but the circular knob, still has space to improve, make it even better, so it is a temporary design.

And about the multi-stop and ensuring fixed position, here is the answer. Now my prototype Byron is equipped with 127/4.7 and 90/6.8 lens, so there will be two infinity stop needed.

A rectangular plate, drilled with two holes, screwed on the flat bed, leaving no spaces of fine tunning, and infinity stop was precisely measured for each lens, then engraved a small gap, allowing front stand to stop at the place infinity stop should be.

Image above shows there are two infinity stop, one for 127/4.7, and one for 90/6.8.

Besides the distance scale for 127 lens, a new scale is pasted at right side, so when 90/6.8 lens is in use, you can estimate the object distance and quickly set, shoot (with a viewfinder mounted in cold shoe). Or you can use rangefinder to focus, then take the readout as reference, set it on 90/6.8 scale, to make precise focus.

How about it? Am I making a wonderful multi-lens exchange system?

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