Monday, June 20, 2011

Rangefinder calibrations on 110B- part3

So actually there are two focus systems, one by focus through lens, and one by focus through RF mirror.
Lens mount on front standard, from infinity to someplace near, limited by the moving range of camera rail, 110B rail got maximum moving range 20.5mm, for 150mm lens, it's about to 1.5m; for 127mm lens, about 1.0m; for 90mm lens, about 0.6m.
Rangefinder rotates mirror to adjust focus, by measuring 127mm lens cam, I found out that RF mirror rotates only 1mm to accomplish focus range from infinity to 1m.

How to synchronize lens and RF? that's what cam stands for. different lens needs different cam, cam with different outer curve. Outer curve comes from lens focal length. for 90mm lens, it can be set focus range from infinity to 0.6m, much wider than 127mm lens (i~1.0m) or 150mm lens (i~1.5m), so 90mm lens cam outer curvature steeper, 150mm lens cam outer curvature flatter.
Later I will show you how to synchronize two systems.

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