1.4 and 2x extenders (1 Viewer)

Does the canon 1.4x and 2x extenders retain AF on 300 2.8IS and 500 4IS?

thanks

kriskent said:

Does the canon 1.4x and 2x extenders retain AF on 300 2.8IS and 500 4IS?

thanks

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I have been thinking along similar lines, comparing 300 f2.8 vs 400 f4. I already have a 70-200 f2.8 which I bought for other purposes, and converted cheaply for birds by adding a 2x extender.

It's not the lens that controls AF, it is the body. Whether you retain AF depends on the body you are using. Each body has a maximum lens greatest aperture up to which it can AF properly.

For 300d / 350d / 20d / 30d that is f5.6. Will the lens / TC combination open up to f5.6 ?

For the 1d variants, I believe that aperture is f8.

I don't know about 10d or 5d.

A 1.4 extender reduces your maximum aperture by one stop :
F2.8 lenses become f4.
F4 lenses become f5.6.

Both lenses listed should AF properly on any of the bodies I have defined.

A 2x extender reduces your maximum aperture by two stops :
F2.8 lenses become f5.6.
F4 lenses become f8.

So, an f4 lens cannot be expected to AF properly except on a 1d variant. However, the 500 lens with 2x extender is really a tripod job, so AF might not be such a critical requirement.

I say "AF properly" because some AF can be achieved by taping pins. I think some of the cheaper extenders can AF to a degree without taping pins.

My choice ? The 300 f2.8 gets rave reviews, the 400 f4 reviews are "just" highly recommended. I don't really have much need for 300mm, so it should be 400 mm. I would expect either to be more influenced by my inadequacies than the minor differences in glass. A 1.4 extender reviews much better than a 2x ... However, I might be influenced by what comes up second hand. I have seen rave reviews for the 500 mm too - in comparison to the 600 mm. Whatever, if you intend to use extenders, get good glass !

A 400 mm f2.8 is definitely out - ££££s ! and kgs I have a fair bit of saving to do even for one of the above.

Mike.