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bob_miller4

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  1. <p>I think the Yashica 50mm/2.0 lenses in M42 mount, including the DX and DS versions, kept the same optical formula. In a non-Yashica M42 camera body, the rear of these lenses might run afoul of the aperture actuator and/or mirror when the lens is focused at or near infinity.</p>
  2. <p>All the Vivitar macro 2X teleconverters with the close focusing ring are multicoated, regardless of mount.</p> <p>By the way, I've thought of one potential reason why a new FD lens can occasionally be hard to mount onto an FD teleconverter.<br> The mounting flange on the teleconverter that faces the back of the lens to be mounted on it has a small groove at the top. (just like the groove on the camera body's flange) The breech lock FD lenses have a round pin that fits into the groove. However, I recall that the new FD lenses have a squared off pin instead that should fit into the groove but might not, if the groove is too snug.</p> <p> </p>
  3. <p>Vivitar sold an excellent multicoated Macro Focusing 2X Teleconverter in Canon FD mount, made by Kino Precision Industries (remember their Kiron products?). Good to like-new used examples are available cheaply online. It's basically a well-corrected 2X with its own focusing ring for "macro".<br /> Here's more from an earlier discussion (there have been several) on this forum:<br /> http://www.photo.net/canon-fd-camera-forum/00YBjE<br /> I have had no trouble using this with a New FD normal lens on an A series camera body.</p>
  4. <p>Meter battery placement in the Spotmatic series was poorly thought out. Many bodies now have battery compartment covers frozen in place by corrosion from old batteries. Canon mechanical SLRs were much better in this regard.</p>
  5. <p>Vodka works on magic marker stains on hard surfaces. Maybe it removes sticker residue, too.</p>
  6. <p>I have a theory that goes like this:<br /> A number of lens manufacturers, Asahi for example, produced SLR lens designs for a time that included rare earth compounds in the glass. Certain examples of certain lens designs give off enough radiation to cause yellowing or read high on a radiation meter, while other examples of the same designs do not. Why?...<br /> ...If the glass contained some thorium oxide by design, in a fixed proportion to the other ingredients, all lenses of a given design made with that glass should show the same telltale signs of radioactivity.<br /> But what if the thorium oxide in it was only an incidental impurity more present in some batches of a rare earth compound than in others, because of lot-to-lot purity variations in a raw material? Or possibly the raw material sources changed over time, or there was some alternation among different sources depending on cost and availability. You could then have lookalike lenses varying significantly in radioactivity.<br /> Someone familiar with Japanese lens-making in that era might be able to support or refute this.<br /> I worked for companies that made partially stabilized zirconium oxide powders that were plasma sprayed to create thermal barrier coatings on jet engine turbine blades. It was known that some zirconium oxide raw materials contained more residual radioactive oxide impurities than others, depending on the original sources of the ore, subsequent purification steps, etc.</p>
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