will this autofocus?

Gary

Gary

TPer Emeritus
Messages
8,561
Name
See above
Edit My Images
No
i'm begining to really struggle for length now (cue jokes :) )

i've got 40d with 1.4TC and 70-200mm f2.8
so, max i can get is 280mm.
at some race circuits its OK, but at others I just need to get a bit closer

will 40d + 2xTC + 70-200mm auto focus?
what f stop will it be at 400mm?

i know it wont be as sharp as a 400mm prime or even 100-400mm but i just dont have the money for any more lenses (wont bore you all again with the story about having everything nicked)

thanks in advance
 
If it's the 2.8 version - yep it will autofocus with the 1.4 converter or 2X converter on any Canon body.

The 1.4 converter loses one whole stop so your effective max aperture would be f4.

The 2X converter loses 2 whole stops, so your max aperture would be f5.6.
 
CT said:
If it's the 2.8 version - yep it will autofocus with the 1.4 converter or 2X converter on any Canon body.

The 1.4 converter loses one whole stop so your effective max aperture would be f4.

The 2X converter loses 2 whole stops, so your max aperture would be f5.6.
Click to expand...

thank ct

will i be able to use all the af points or just the centre one?
 
Sadly - centre one only - even with a 1 Series.
 
Errr.... I don't normally disagree with CT, but my 40D+2X+70-200 does autofocus using all or any of the 9 af points :shrug:

Mind you, the results are nothing to brag about - soft and slow :thumbsdown:
 
tappilappi said:
Errr.... I don't normally disagree with CT, but my 40D+2X+70-200 does autofocus using all or any of the 9 af points :shrug:

Mind you, the results are nothing to brag about - soft and slow :thumbsdown:
Click to expand...

Well don't argue again - especially if you're going to be right! :baby:

LOL Dunno what happened there - blame Jack Daniels I think. :D
 
1d series can focus to f8 all other bodies upto f5.6 iirc
 
MattF said:
I thought the 2x TC only focused on 1 series bodies?
Click to expand...


That depends on the max aperture of the lens you're using.

1 Series will still focus as long as the effective max aperture is f8 or larger (with the converter)

With all other Canon bodies AF works with converters as long as the effective aperture is no smaller than f5.6.

It's another good reason for buying faster lenses. ;)
 
Yup, I agree with 33L. Although I have heard/read that you can do a dodge with a piece of sticky tape on some of the lens contact pins to get af after f5.6 on xxD bodies.... never tried it though :shrug:
 
Also, unless the subject is relatively still, I find that the af is so slow (with a 2X) that I get better results by focusing manualy
 
I really don't fancy the sticky tape trick given the price of the kit at either end of the converter - call me cautious!
 
oh yes i agree with CP its there for a reason and probably so you dont damage your lens/body!
 
The 70-200mm f2.8 most deffo does AF on the 40d, it does make the lens a f5.6, although i have no examples from this year uploaded as i use the 400mm f5.6 prime for motorsport. However i do use the 70-200mm f2.8 for other stuff and just carry the 2xtc incase.

Heres one from last year taken with the 30d.
Hosted on Fotki

Useable?

As for difference between the 70-200mm at 400mm heres a crop from a test
Hosted on Fotki

same shot and conditions with the 400mm prime.
Hosted on Fotki

No processing done to either image.

Sure you more then aware how much better the AF between the 30d and 40d, but the 400mm prime is much much faster then 70-200mm f2.8 + 2xtc, but its still useable.
 
Good examples,

Asking a doubled up Zoom to compete with a prime is a big task, I think it does well.
 
33L said:
oh yes i agree with CP its there for a reason and probably so you dont damage your lens/body!
Click to expand...

The tape trick will In very good light AF without much problem, however in good to poor light it will hunt like buggery, particularly in AI servo, this can cause the lens motors to get very warm, and would risk burning them out.
 
You must log in or register to reply here.
Back
Top