Quote Originally Posted by HiFiGuy1
I am also sort of wondering,based on the age of the current 400mm f/5.6,if Canon will be releasing a 400mm f/5.6 IS which may or may not also have a much shorter MFD, and in the near future. A four-stop hybrid IS 400mm f/5.6 would be awesome, and I would have to consider selling a body part for it.

That would be a nice lens, but IMO it still would not compensate for the loss of AF sensitivity due to f/5.6.


The more recent 1-series bodies' center-point AF is cross-type up to f/4 and linear up to f/8. That is a whole level of awesome in itself. While every EOS body has center point AF up to f/5.6, it is not cross-type. And again, on most bodies, peripheral AF points don't even work at f/5.6 (though they do on the 1-series).


The funny thing is, I was just shooting some birds on a bayou with my Nikon D100 with 400mm f/5.6 Sigma alongside my 40D with 28-135mm yesterday at "golden hour", andIhave become a little disenchanted with the AF of the Nikon/Sigma combo in less than full daylight, so I have been considering selling the whole kit andbuying a Canon tele with the money. While I was shooting, though, I also realized that some of my shots really needed much more than 400mm, so Iam kind of nervous about a 300mm, which is obviously shorter. Being limited by available funds, I want to make my next lens be as flexible as possible, but with outstanding IQ.
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Well, first of all, you're using a low-density DX sensor with a third-party f/5.6 lens, so it should not be terribly surprising that the AF performance is poor and the reach is insufficient. If you were using a high-density APS-C sensor with a faster f/4 lens, you would be well on your way to rectifying those shortcomings. But it doesn't sound like you really intend to work near MFD with the super-teles if you say you can't get enough reach. There is no substitute for a 400mm or 500mm lens. You may have to consider saving for an EF 500/4L IS, which with a 1.4x II gives 700/5.6. There isn't any way of getting much further than 400/5.6 with anything less than the big whites (unless you go third-party).


Once you go beyond the 77mm front filter diameter, you enter a whole new realm of imaging...and cost.


If anything, you should rent the 300/4L IS, 400/5.6L, and EF 1.4x II, slap them on your 40D. You will immediately find (1) AF performance with the 300/4L IS is superior to the D100+Sigma; (2) Crop ability is superior due to the higher sensor density in the 40D over the D100; (3) 400/5.6 AF may be slightly less impressive, and perhaps even undesirable in low light situations. What you really need for birding is a 500/4L--relatively light weight, long focal length, and wide aperture. That is, unless you are me and have a peculiar obsession with hummingbirds.