hrblaine

>[Fluorite is one of the reasons Canon telephotos are painted white.)[/quote]

You lost me on this one. Care to explain? Harry

Lucian Loc: From Wales, living in Ohio

No Holds barred, you mean!

Now that is a pretty creepy artificially blurred hand you have there on the belly of that baby. It might have been better left as it originally was, since the hand was in the same focus plane as the baby and would not normally have been blurred.

amfoto1 Loc: San Jose, Calif. USA

Fluorite is a fairly fragile. Various manufacturers who have used it in their telephotos have painted them lighter colors to minimize heat gain while out in the sun, which can lead to metal expansion that might in turn cause damage to the fluorite elements.

Canon took this route when they incorporated fluorite in a lot of lenses. Since they've also done similar paint jobs on some non-fluorite telephotos, they probably also noticed the "marketing" value of making their lenses so distinctive. In the past there have been many observations of all the "big white Canon lenses" dominating the sidelines at major sporting events, for example.

This is less distinctive now, since Sony has started painting a lot of their telephotos a similar off-white color too (even though no Sony lenses use fluorite).

From an engineering standpoint, it's now probably largely unnecessary, too. Nikon appears to have no problem with their black painted lenses that contain fluorite elements. New materials and/or more rigid designs or new lens element mounting metals that avoid problems metal heat expansion are probably what make this possible.

BTW: Back in the early days, one of the reasons NASA cited for rejecting Canon gear for use in space was out of concern that fluorite in certain lenses wouldn't hold up to the stresses of rocket launches. Initially they chose Nikon and Hasselblad gear, instead.