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| p.11 #4 · Announced: EF 16-35mm f/4L IS and EF-S 10-18mm lenses |
...ultrawide zooms having non-sealed front elements. Is the 17-40 the same?
The published MTF doesn't give performance in the middle of the zoom range. We saw with the 24-70mm f/4 IS that the MTF was silent about the performance sag @50mm...
The kerfuffle about that was more in photo forums than among reviewers or those reporting on photographic results with the lens. The use of the (literally correct, I suppose, from one point of view) term "sag" to describe the lens's performance at 50mm suggests a problem that isn't actually there.
Basically, what it amounted to was that the uniformly excellent tested performance of the lens was slightly less excellent but still very, very good at 50mm. (Unless you imagine a lens that does not differ in its performance characteristics in any way at different focal lengths and apertures — basically the "impossible lens" — a reviewer or forum poster can always write "performance is lower at [measurement X]," but this is basically meaningless.
Paul Mo wrote:
Buy quality, get off the treadmill.
Yup. I'd add, "buy carefully and make sure that you are buying things you actually need."