K K Hui wrote:
>
> Because of the relatively large aperture (f/2.8) for a 400mm, the DOF is
> extremely shallow when used wide open and hence accurate focusing is
> essential for obtaining sharp images. The lens definitely
> needs to be stopped down to achieve sharp image when used with either
> the EF1.4x or EF2x converters. At least that is my personal experience.
> In fact this is further confirmed if you take a look at Canon's
> published MTF charts in their EF Lens Work II.
I hate to disagree with you but I had the opposite experience. I had a
400 f/2.8 II L lens for about three years. I shot tens of thousands of
slides with it, each and every one wide open. Probably a third with no
extender, a third with a 1.4x and a third with the 2.0x extender. I
think it's the sharpest lens I ever owned prior to my new 500 f/4 IS
lens. As far as sharpness, I consider them equal. I know lot of people
who use the 400 f/2.8 and they also think it's fantastic. Everyone I
know shoots it wide open. The background blur on the 400 is far better
than the 500 f/4 IS. I used the 400 almost exclusively for bird and
wildlife photography. I used it 100% on the large carbon fiber Gitzo
tripod with a Wimberly Head. I cannot remember Canon's MTF chart but it
seems that Photodo rated it the second highest rated lens in the world
slightly behind one of the Leica monsters. I hope you lens is not a
lemon.
Ray Amos
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