On 11/6/2014 8:08 PM, Chuck Norcutt wrote:
I have to think about that one a bit.
Mercy! Look, don't ponder!
I've only heard of such things but never seen one. It leaves me very curious since lens tubes both expand and shrink
with temperature. If there is sufficient linear expansion to cause focusing error when the tube shrinks with cooling
temperature there is also sufficient change in length to cause focusing error when the tube expands with temperature.
Thinking too simple still. Think complex zoom, with all those different parts
inside being changed in size by temperature.
The "past infinity" would occur with a shrinking tube but a "short of infinity" would occur with an expanding tube.
It seems to me both situations are equally likely but I've never hear of a tube marked for both nor one with specific
temperature recommendations.
Does anyone have an actual lens so marked and with instructions how to use it?
I don't believe I've ever seen instructions talk about it. But who knows; it's been a lot of years, I've read a few lens
instruction sheets/manuals, back when they had them. But I've ignored or never received many more. IF I remember
correctly, I was curious and looked it up.
Anyway, there are a couple of examples under the Tamron heading here. <http://www.kenrockwell.com/tech/pma07-c.htm> I
know I saw them before digital, but on which lenses ... ??
Infinity, Wherefore Art Thou Moose
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What if the Hokey Pokey *IS* what it's all about?
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