Canon 50D vs 40D AF

Hi all --

I have a Canon 40D which I like but I find that AF is a little slow to lock on and to track fast moving and erratically moving creatures (purple martins, butterflies, dragonflies, swallows, etc). I'm considering buying a 50D and have read that while the AF system is the same as that of the 40D, focus functions a bit better thanks, perhaps, to the improved processor.

I am hoping someone can give me some good advice about this. The lenses I use are Canon's 100 macro, 70-200f/4 IS, and 100-400 IS.

Thanks in advance for your time and advice.

Kent,
While I don't have 50D experience, I can say part of your frustration with slow AF is probably the 100-400 lens. I have one (100-400) and the AF is slow compared to other (non zoom) lenses, like a 300 f/4 L IS, or, a very fast AF lens like the 400 f/5.6. Of course, for really fast AF, try the 300 f/2.8 L IS. A 1D series body does much better at AF than the X0D series in my experience (again no 50D experience). There is a thread that shows the 50D to be very good. I bet the lens played a critical role too in that case.

Roger

Hi Kent Agree with Roger on the lens being on the slow side but you should be getting better results. Remember to use the limiting setting on the lens, always prefoucus and initiate the AF with the center point !!

For flight the 400 5.6 is about the best hand held lens you can get. Fast AF, sharp and not expensive !!!

Kent,

The 100-400mm is slow on the AF even on my 1D Mark III and the 50D I have.

I believe that the 50D has much better AI Servo performance than the 40D, and also does a much better job in low light and low contrast situations. However, as Robert says, the 100-400 is a slow lens when it comes to AF. The 400 f/5.6 might be worth considering rather than a new body; you won't believe the difference compared to a 100-400, even on your 40D.

I think Doug has it right on the money.

Thanks, guys. You have been very helpful to me. As usual, BPN is terrific.

Here is a fact. A skilled photographer with a 40D and any lens will make better flight images than someone with a 50D and the same lens who is clueless. Operator error or operator proficiency is a huge factor in discussions such as this. Someone said in a similar vein that most lenses are a lot sharper than most photographers....

Guilty as charged! At 71, cataracts, and a left eye full of floaters from having had a detached retina, I have no doubt operator error is a frequent cause of the shortcomings in my photos. I don't think I'm clueless, however. A couple of the images I posted of purple martins with dragonflies in their bills aren't so bad (IMHO). I'd just like to do a lot better.

I did, however, take some of the advice offered above and got a 400 f/5.6. I'm going to try for eagles on the Mississippi at the end of January.

Quote:

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Originally Posted by Kent Wilson

Guilty as charged! At 71, cataracts, and a left eye full of floaters from having had a detached retina, I have no doubt operator error is a frequent cause of the shortcomings in my photos. I don't think I'm clueless, however. A couple of the images I posted of purple martins with dragonflies in their bills aren't so bad (IMHO). I'd just like to do a lot better.

I did, however, take some of the advice offered above and got a 400 f/5.6. I'm going to try for eagles on the Mississippi at the end of January.

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If you are making any sharp images of purple martins in flight we do not want to hear about either your old age or your allegedly poor vision :D :D

You got me (again). I surrender. :-)

Thanks for offering this web site. It's been an enormous help to me. I refer every photographer I speak to take a look. Best value I know of. --- If I keep up the good words, will you sell me a 500 IS cheap? Even if you would, I still couldn't afford it. My wife would leave me! :-/

Oh yeah, and have a happy holiday!