Originally posted by Frogfish It would also help if you read through the thread properly instead of jumping in the middle ... then you'd know what I was referring to. I did mention, but it seems you chose not to bother reading through the thread again, already that the links were in this thread (or the other main 560mm thread) on this very subject, whereby a US Govt study no less stated there was no difference between white and black painted cars in regards to heat absorbtion. Nikon seem to have understood this.
Sure I jumped in the middle, I've only been lurking through the both threads looking for nice little tidbits on the new 560. The plain fact is that black objects absorbs heat better than white objects. I suggest you look up the concept of albedo. As for that US Government study that you pointed out, please provide a link so we can take a look at it.
As for Nikon and Sigma's black lenses, have you ever considered that perhaps they use a different method of combating the heat? White makes a great way of reflecting heat. SIlver moreso. Space probes and satellites take advantage of this.
As it turns out, black is better for re-radiating that absorbed heat too (the concept is called emissivity). What does this prove? That the issue of white vs. black and heat is more complicated than most people think.
White lenses may not heat up as fast, but black lenses probably lose that heat faster (once there's some shade or a good breeze).
Frogfish, I am only asking for proof. You have provided none as far as
lenses are concerned. Proof would be a technical paper from Nikon or Canon explaining this, or some scientifically minded person performing well thought out experiments with actual lenses (and not cars). Something along those lines, not an an analogy (black vs. white cars) that may not apply because it's cars vs. lenses. It also depends on the testing methodology used and the exact circumstances.
EDIT: You know what, enough of this prattling on the merits of black vs. white, let's get back to how much this dang lens will cost, and when it'll be available for purchase...