Why are there different hood sizes for the same focal length lenses?

Question

While comparing the 85mm f/1.4G to the 85mm f/1.4D I noticed the lens hood size is noticeably larger on the new lens. You can see the difference down the page here

While I could understand a little difference, I would expect for them to be most effective, the same focal length would have roughly the same lens hood from lens to lens. Why the difference? Or are my eyes just fooling me because they're constructed a bit differently ?

Asked by rfusca

Answer

Two reasons. The method of attachment is different, which accounts for the difference at the rear. The old hood screwed on to the filter thread, while the new one bayonets to the outside of the lens (and is thus reversible for storage).

That leads directly to the second reason: the old hood had to accommodate for the possibility that filters would be attached between the lens and the hood, so it couldn't be as long as it might otherwise have been without causing vignetting. Once you allow for a worst-case, but normal, filter stack (a polarizer and a colour correction or ND filter), there isn't a whole lot of difference in length between the two. On the newer lens, the filter stack would form a separate system inside the hood rather than being part of the hood system.

Answered by Stan Rogers

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