Quote Originally Posted by neuroanatomist


Quote Originally Posted by Richard Lane


If you are using a variable aperture lens, does the lens open to the widest aperture that the lens offers or the widest aperture at the current actively used focal length, letsuse the 100-400mm f/4.5-5.6L as the example.


In other words, if I'm at 400mm with that lens, will itopen to f/4.5 for AF or f/5.6?


It will use the widest available aperture at that focal length (e.g. f/5.6 at any zoom setting of 260mm or longer). It's a physical thing - at 400mm, the 100-400mm f/4.5-5.6L lens cannot open to f/4.5 because the optical elements are not large enough in diameter. That's also the reason the 100-400mm is ~$1500, while the forthcoming 200-400mm f/4 will be in the high thousands - the extra glass needed to open that wide at the long end.


Sorry to burst your bubble, but the 200-400 f/4 that was advertised is simply a model. A close relative of mine who spoke with some Canon higher-ups found out that the lens is only in design phase, no where near production and won't be in production for a long time, if at all. Its heart-breaking news and I almost hope they lied to him. But it does explain why no one was able to handle the lens when it was shown off.





Guess the 100-400 will have to suffice for a while longer.


Mike