Leitz Loc: Solms

Unlike you, I am not here to argue or insult. It is a well known fact that metal and glass expand when heated - it is also a well-known fact that such expansion DOES negatively affect the focal point in certain lenses. The link I posted earlier is but one of many references that may be cited - the "Nikon Compendium," page 137, is another. Not everyone is capable of understanding elementary science, of course, and I end my participation in this thread.

boberic Loc: Quiet Corner, Connecticut. Ex long Islander

While I most certianly agree that most things expand when heated and then contract when cooled. This is guided by the coefficient of exapansion. This differs for each material. the primary factor which controls how much expansion or contraction is the length of the item. The lengths of materials in a cemera lens is very short, a matter of inches. If you were to look up the specs for how much a given material expands, you will find that the coefficient is listed in fractions. This number is listed in feet. this mean that an item the length of a lens would expand is a small fraction of milimeters. Such as .060mm/feet. The manfacturer taks this into account when building the lens and allows for the very small changes of length. These tolerences are accounted for in the construction so that they do not damage or change IQ for the lens or for that matter the camera. Therefore the changes as a result of sun heated lenses relative to performance is a non Issue. Neither Canon Or Nikon or Sigma or Tamron makers are not so stupid t=so as to allow sun heated lenses to affect performance.

Mark7829 Loc: Calfornia

We all understand heat but for this is not a significant issue. It is not a reason to switch to Canon. Blah, it is nothing, not worthy of a comment on this or any other forum. How many of us are going to be hand holding anything in 125 degree heat? A white lens with a black camera body is not going to be any different than a black lens on a black camera body.

Photocraig

Your astute comments make this sometimes confusing market segment more understandable. Companies have their perdtermined "truths" and prejudices and above all Corporate Egos's. Of the 4 old Canon EF compatilbe lenses in my bag, my Tamron 90mm f2.8 SP lens in my best lens. My only complaint is the 90mm on an APS-C camera makes portrait shooting a distance event.

Warranty is a technology and financial issue. While a product might be the best and most reliable, the contingent liability of an express warranty can have ramifications on the financial statements and earnings reports. The classic tail wagging the dog. The warranties from Sigma and Tamron add to their credbility and minimize the customer's reliabiity risk of buying third party products.

My personal reaction to the Sigma re-mounting offer is curiously emotional. Changing systems is a huge commitment in investment and learning. If I chose to switch, it is an unquantified "comfort" to me that Sigma would help me re-purpose my lens(es). Especially if they represented $1,000+ investments.

The warranties and the Sigma re-mounting and the USB doc give me confidence in a Sigma purchase. That's good business practice, communicatied by excellent marketing. It shows that Sigma understands their market.

ptcanon3ti Loc: NJ

The following are my observations over a period of 2 weeks of Mark7829.

ANYONE who tries to participate in a thread discussion but who happens to have a different opinion or disagrees with #7829, opens themselves up to attack. #7829 will instantly go on the attack and will promptly begin throwing vitriol, disrespect, anger and insults - to all those who have a differing opinion from his. Whether that differing opinion is based on research, experience, or is simply an opinion, does not matter. #7829 will relentlessly attack the person until they become disgusted with his abhorrent behavior and leave the thread.

When it suits him, #7829 will begin calling for lab test results, or links, or other verifications and proof to refute his opposing argument. Of course, no one offers such information, because they are familiar with the “internet bullies” of the world, and have long retreated from the thread.

This is sad because as willing participants in various conversations/threads depart the thread, we all lose because of the loss of varying ideas and experiences of others.

Here are a few #7829 quotes from THIS thread.




This is all rather bizarre and sad because #7829 has dedicated a good part of his time to actually learning photography. But his abhorrent behavior is so repulsive to most here on UHH that his abilities are wasted.

I will now sit back and wait for the attack to come, and smile as the prophecy fulfills itself.

MT Shooter Loc: Montana

Stopped by the store to drop off a shipment, here is a direct mailer from Canon, pay especially close attention to page "8" which defines their L lens designation.

Can you say "ambiguity"? ;) ;)

http://software.canon-europe.com/files/documents/EF_Lens_Work_Book_2_EN.pdf

Screen shot of page 8

(Download)

Mark7829 Loc: Calfornia

Really? How would you react to the comment that Canon lenses are superior to other lenses because their white color does not absorb heat? Asking for a legitimate link to a certified lab is just common sense.

Or how about the comment that an f/1.8 lens will always focus faster than a f/2.8 lens. To ask if that came from a certified and reputable lab with empirical and supporting evidence would be appropriate. Would it not?

Who would not ask for supporting documentation?

And if you can not support the claim then asking the individual to just shut up seems appropriate. My quest is only to get the best information out there so we can all learn, and to have members check their own sources before making gross mistakes and misleading statements. How can that be unfair?

RWR Loc: La Mesa, CA

I sent the same link that Leitz mentioned on page four (http://cpn.canon-europe.com/content/education/infobank/lenses/black_or_white_lenses.do) to another member yesterday, but it was not posted (I didn't want to get involved in the argument). It states that the focal point may change when the lens heats up, and also why not all Canon lenses are white. You may want to read it. I also have a copy of the Nikon Compendium (from 1995), where the author states (regarding thermal expansion) that a few tenths of a millimeter is enough to affect the focal point.
My own thoughts are that lens barrel expansion has more effect on the focal point than glass expansion.

imagesintime Loc: small town, mid-America

Buy that doesn't say fluorite is used in each L lens. The list I posted earlier, also from the Canon Europe site, shows the specific lenses that use the fluorite crystals vs. those that use UD or SUD lens components.

imagemeister Loc: mid east Florida

I agree with the physical thermal expansion degradation possibilities - but really I am MORE concerned with adverse affects on the electronic circuitry in the lens as it pertains to AF and IS.

Mark7829 Loc: Calfornia

Here is the comment

Most EF lenses have black barrels, but a few are white (actually a light grey or beige). The white lenses are all large super-telephotos. There is a good reason for this.

Lenses contain glass elements. These expand with heat. This is not usually a problem with compact lenses − the amount of expansion is small. But large lenses contain large elements and here expansion can bring a lens close to the limits of its design tolerances. A white surface reflects sunlight, helping to keep the lens cooler.

Incidentally, you will find that the manual focusing action of some black lenses allows focusing past its infinity setting (sometimes called over-focusing). This is also to allow for expansion. If the lens is used in hot conditions, infinity focusing will be closer to the end of the travel.

The only thing it says that high heat will bring the lenses close to their tolerances. It does not indicate distortion, focus issues or any problem what so ever. It also does not mention how much heat. Are we talking about 90 or 3000 degrees. This is not a problem for most if not any of us and not worthy of even the posting. And finally their is no comparative analysis between two lenses one white and one black. Some lenses are more plastic than brass, how does that contribute or not to the issue? Since there is no actual empirical data/evidence. No thermal readings, no actual images comparing cool vs heated. This is not an issue at all. I would love to see examples to prove any of the assertions and/or problems.

Common sense is to always to protect your equipment from the elements.

imagemeister Loc: mid east Florida

Or, just bury your head in the sand .....

RWR Loc: La Mesa, CA

My only long autofocus lens is a 400mm, with no IS, and it's only been used in the shade of the forest, so not exposed to heating from the sun, but I certainly agree that your concerns are probably legitimate. My old Kokak P-850 digital didn't like 100° in the desert, but the Nikon F4 was good for at least 115°. That was before I had sense enough to stay home when it got over 100°! :lol:

juicesqueezer Loc: Okeechobee, Florida

Wow! I did not know my statement about white vs. black would draw this much heat! lol
Nikon has made some off white lenses in the 70-200 f2.8 and I believe the 300 f2.8. However, most are black, so not sure why they offered the off white except to give that look that canon offers with some of their white lenses.
I shoot a lot of RC airplane shows and believe me when I say, its hot in south Florida when doing these shoots! I have never had a problem with my all black lenses and black bodies. Just my most humble opinion on this matter!

RWR Loc: La Mesa, CA

This tells me that as the hot sun beats down on a lens, the elements DO change their position relative to the focal plane, however minutely, which cannot fail to alter the focus point.