Can't find 40D neg feedback post on AF+TC

[shoshone]

Folks I tried to search for something I'm sure I read on this forum which related to 40D + 100-400 + 1.4xTC with taped pins.

Sort of decided that a 40D (with the 100-400 sometimes + canon 1.4x) would solve my birding problems. The 5D would therefore have the 24-70 2.8L on all the time.

However I'm sure I read about an AF problem on the 40D with this setup. Can anyone point me to this post please, or offer advice?

Jamie

[JohnZ]

There was a thread on here regarding the lack of AF using the combination you have mentioned. I believe the general consensus of opinion was that, strangely enough, the combo did not work using centre point focussing. However if you chose one of the other focus points it appeared to work.
Sorry but I cannot remember the name of the thread. I will have another look.

[JohnZ]

Try "Dividing by ten".

[shoshone]

Try "Dividing by ten".

John,

Many thanks for the help. I'll go there to ask further questions

jamie

[awallace]

I also read that it doesn't work, but here is a chap that clearly demonstrates that it does...

http://www.youtube.com/watch?v=STvuECPWR7c

[Roy C]

As John said most people have found that the taped tc trick does not work very well with the centre focus point but is fine if using any other focus point. This is most certainly the case with the 400mm f5.6 prime and 40D.

[David Smith]

I also read that it doesn't work, but here is a chap that clearly demonstrates that it does...

http://www.youtube.com/watch?v=STvuECPWR7c

I have been able to get it to work with 'centre point' when pointed at something obvious i.e. side of a buiding but not while trying to focus on something small like birds. I can't get sound on my computer (technical glip) so don't know what the guy said but I don't think shooting the tower is going to prove it works with birds (I'd like to be proved totally wrong)
I'm waiting for the weather to coincide with time/opportunity to give it a real trial.
It's interesting that Keith Reeder seems to have reverted to doing without the 1.4TC and stated he hadn't missed it like he thought he would. However, I would like to use the TC and am hoping someone will come up with the magical solution.

[awallace]

David - There is nothing much in the commentary of the video. He is using the centre point for AF, and defocuses manually a couple of times. Focal length is 400mm and he uses a Kenko 1.4xTC. Obviously this is quite a simple subject for the camera to fucus on, but the response seems quite quick. He doesn't describe what happens with AF on moving subjects though. It would be very interesting to hear how you get on when you manage to get out.

[Roy C]

I also read that it doesn't work, but here is a chap that clearly demonstrates that it does...

http://www.youtube.com/watch?v=STvuECPWR7c

Works ok if you want to shoot pylons and sides of house's but it ain't a lot of good with birds I can assure you ;);)

[Roy C]

However, I would like to use the TC and am hoping someone will come up with the magical solution.
I think the only magical solution to this one David is a faster lens, a 1 series Camera or using one of the other focus points.
I have tried a Canon tc with one of the outer focus points and it focussed very quick with my 400mm f5.6 - probable better than the 30D ever did (not quite as good with the Kenko pro though)

[David Smith]

or using one of the other focus points.
I have tried a Canon tc with one of the outer focus points and it focussed very quick with my 400mm f5.6 - )

Roy
I've not got my head around this yet. Being quite new to DSLR I have never tried other focus points-in my mind I can't see why (under normal circumstances) you would use anything other than centre or average (to use old terminology). As I say, I'm new and have never tried it so this is not a critisism-I just don't yet see the value (apart from the fact it makes the TC work)

[Roy C]

Roy
I've not got my head around this yet. Being quite new to DSLR I have never tried other focus points-in my mind I can't see why (under normal circumstances) you would use anything other than centre or average (to use old terminology). As I say, I'm new and have never tried it so this is not a critisism-I just don't yet see the value (apart from the fact it makes the TC work)
I use the centre point only for 95% of the time. Only times when I do not is :

a) For birds in flight when there is no distracting backgrounds I very often use all focus points and AI servo mode - although you must initailly lock-on with the centre point if you lose the bird in that point, any of the other points will lock on to the bird thus giving you a better chance.

b) When taking landscapes with a locked tripod and I want to focus on something about a 3rd into the scene (to get everything in focus) the only way is to select a focus point which covers the desired focus point (or manual focus).

Using a focus point other than the centre for normal bird shots would certainly be a bit alien to begin with but I would not have thought it would be too much of a problem after you get used to it.