“The problem solved by a white lens casing is exactly the one you mock. A black lens heats up at a different rate from the lens elements and other mechanical parts. There are little motors in there, and plastic and rubber parts that can melt. White adds longevity. Every long lens worth owning is a pale color for this reason.
Tamron made a ‘cammo’ color 300mm. It’s still pale green.”
—commenter on a previous blog entry
I understand where he is coming from but my mocking is the purpose of this blog: it is designed to make you think about the reason for things and to back it up with facts.
The problem with “the problem” is that “the problem” isn’t a problem.
As I mentioned before, the solution only applies to very large solar telescopes and it solves not the fact that that anything melts, so much as the optical properties change due to hot air convection inside the very large scopes that spend all day staring at the sun.
In tests, painting a lens white doesn’t even create more than a couple degrees difference for a 35mm telephoto lens after an hour of shooting in the Death Valley sun. One or two degree difference isn’t going to make any difference optically for even the largest 35mm telephotos, or with the wave motor action, or whether the rubber parts melt.
Ask yourself why Canon doesn’t paint white where temperature matters the most—in the the camera body where the sensor is temperature sensitive. Ask yourself why they use silver metal construction in the gorgeous ELPH series of cameras when silver is the exact opposite of white for the conditions he mentions—unpainted metal has an inability to radiate heat. Honestly, if it made any difference optically, do you think the top optics companies of the world would have missed this before Canon figured this “brilliancy”? He must have a really low opinion of Nikon, Zeiss, Schneider, Leica, and the like to believe that Canon would beat them to an optical advance such as that!
The reason for the white lens, directly
Canon uses white to distinguish L-series lenses from others just like Nikon uses a gold ring. This was a marketing ploy inherited from large solar telescopes and then, via a Takahashi homage, copied by Canon. Other lens manufacturers try to ride that silly “white lens” coattail that Canon has created in sport photography by painting their long lenses white.
Bicycling on continental
Continental is a respected German brand of bicycle tires. The quintessential characteristics are dark threads in the tire casing and metal tire beads that are manufactured slightly smaller around than the tops of most wheel rims.
The two conspire to create the illusion to the consumer that they are built tougher.
There is nothing special about the casing other than the color—which acts as a trademark for Continental much like painting a lens white and adding a red ring does for Canon. As an engineer, I understand that it is the inner tube pressure that holds the bead against the rim, not manufacturing a too-short bead.
Since I know this, changing the tires on my bicycle after a flat is often occasioned by much unflattering commentary from me concerning the German engineers’ tendency to uselessly overbuild things and not trust basic physics.
You can get me to like the aesthetics of the Conti tires dark casing or the rigid feeling of the beads. But don’t go telling me that this is superior from an engineering standpoint. I’ll mock you and tell you to not let the facts hit your ass on the way out of this blog.
Why I mock the white lens
The same goes true for “white” photographic lenses:
Wax all you want that to you a white lens is aesthetically pleasing, signifies better build quality, and looks more professional (we can agree to disagree on matters of taste). But please don’t give the tired old “white reflects heat” naïve explanation of why Canon paint their expensive lenses white.
Sooner claim the gold ring improves optics by making the lens casing more rigid and holding the optics in place. After all, “every lens worth owning” has a gold ring for this reason.
And yes, Tamron puts a gold ring around all their best lenses. 😀