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Old 03-13-2018   #22
Sarcophilus Harrisii
Brett Rogers
 
Sarcophilus Harrisii is offline
Join Date: Jun 2009
Posts: 2,570
Quote:
Originally Posted by Philip Whiteman View Post
Ha ha! It did take rather a long time to fix it properly, but yes; it's a year's use I have had out of it (and its shutter runs more smoothly than any of my other Contax IIs or Kievs, even if one of them - my Kiev 2 - runs it very close).

I think it's worth repeating here that I used the Japanese silk ribbon, available online, and found the shutter ran perfectly without messing around with the guide slots in the lower curtain.

It is also impressive that every single Contax II (not IIa) and Kiev I own has pretty much perfect rangefinder alignment and calibration. That prewar rangefinder was a fine design!
The RF system used in the II and III is even more impressive than many observers realise. Too often, comparisons only take into account the effective rangefinder base length. Achieving a long effective base length using viewfinder magnification will increase accuracy. But what is usually overlooked is that it is still inferior to using a physically longer base length. The effects of any lack of tightness of design tolerances of the rangefinder system components, such as in any pivots and linkages from lens to mirror and the mirror pivot itself, for example, (plus any production deviations from design), are also going to be magnified by the viewfinder, and this impacts accuracy.

Therefore: if two rangefinders using a similar lens-actuated mirror system share an identical effective base length, the example with the shorter physical base length must be both manufactured and calibrated with greater precision, than that with a longer physical base length but lower viewfinder magnification, to achieve the same overall accuracy. And if the precision of the longer type matches that of the shorter, it will (all other things being equal) always be superior: even if the EBL of both types is the same.

Further, the Contax II/III feature a pair of swinging optical wedges rather than a rotating mirror type rangefinder. These wedges require a mechanical movement that is four times greater than an equivalent rotating mirror to achieve the same beam deflection, and the result of this is a corresponding four-fold increase in accuracy.

Thus, not only do the II/III feature an exceptionally long physical base length with moderate 75% viewfinder magnification (according to Stephen's page on the type), but, the use of a swinging wedge beam deflection system greatly enhances accuracy on top of that. I believe that, technically, it has yet to be surpassed either by the post-war Contaxes, or anybody else.

It's not uncommon for found examples of the II/III to retain the factory calibration of their rangefinders, but the original adhesive that fixes the wedges may be ready to fail. So, before I clean an example with accurate calibration, I always place minute dabs of 5 minute epoxy on the extreme edges of each of the wedges where they meet their mounts. This ensures they remain securely locked in place in the correct positions for some time to come.

Cheers,
Brett
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