-=FAQ=- Teleconverter/T-Con Tele extender Discussion

perryge wrote in post #4579785
I use the Kenko 1.4x with the 400D and Canon 70-300 IS and it works, no problem, autofocus works fine.

thanks. are you using the 1.4x pro 300 dg? worst case i guess i can get one try it and see.

mike_k_23 wrote in post #4579890
thanks. are you using the 1.4x pro 300 dg? worst case i guess i can get one try it and see.

That's the one!

Anyone point me to some samples of a 70-200 2.8 IS (or non-IS) using either a 1.4x or 2x Kenko teleconverter?

Thanks

BrantG wrote in post #4628606
Anyone point me to some samples of a 70-200 2.8 IS (or non-IS) using either a 1.4x or 2x Kenko teleconverter?

Thanks

https://photography-on-the.net/forum/showthre​ad.php?t=141406

Thanks a bunch Cyber

This may have been posted somewhere within the 19 pages of this thread but the Canon 1.4 TC (and I would assume the 2.0 TC) IS compatible with the 70-200 f/4L IS lens. The list in the first post of this thread does not list this lens but the Canon website confirm it is a compatible lens.

CyberDyneSystems wrote in post #284167

Any EF-L Telephoto listed above, it's older brother (non IS etc.) will "fit" as well

The 80-200mm f/2.8L will not fit the Canon TCs which is the 70-200mm f/2.8L's older brother.

Good catch Adam,. I forget that was the predecessor.

Just thought I'd add to this long thread. I recently picked up a used Kenko 1.4 300 dg. Taped the 3 pins, mounted between my 100-400 + 5D and....

Seems to focus just fine. I haven't tested it for accuracy, yet. I will do that soon.

Probably a stupid question - but does it matter in which order the Canon x2 and x1.4 TCs are stacked in a multiple set-up?

If I remember right, they only go together one way.

You have to put the 2X on the lens, and the 1.4x can stack behind the 2X,. it won;t fit the other way around.

It's also the same for the new Sigma 2x and 1.4x.

Ah, right. Thanks. I plan to buy the x2 Extender in a fortnight as a stop-gap until I can afford a proper big beastie.

You have to think about it from two different approaches:

REPORTING THE INFORMATION TO THE CAMERA.
I'm talking about reporting the resultant focal length and aperture. With this information a TC-aware lens is able to change the table it uses to calculate the AF, and also reports it to the camera.
Thus, it is a good policy to tell the lens and the camera the closest information to the truth.
Let's talk about puting a 1.4X and a 2X stacked on a 200mm f/2.8.
The resultant is a 2.8X teleconverter, and it will give us a 560mm f/8.
We are trying to make it work on a 50De (yeah I know... sometimes I already live in 2009, sometimes in 1996 with the ElanIIe AKA 50e, with ECF).
a) If we stack it in this way : lens 1.4X 2x camera then the 1.4x hasn't the reporting pins at the camera side so it does not notice there is a 2x there.
The 1.4x reports to the lens it's there and the lens reports that there is something that works like a 280mm f/4.
b) If we stack it in this way : lens 2x 1.4X camera then the 2x hasn't the reporting pins at the camera side so it does not notice there is a 1.4x there.
The 2x reports to the lens it's there and the lens reports that there is something that works like a 400mm f/5.6.
In the case (a) both the lens and the camera work with an information closer to the truth an will have less chances of an AF failure.
Hope that it will AF with the 50De
NOTE: this is only theoretical, but it'd be very strange if it works in a different way. (Hehe try to get a 50De to demonstrate it)

IMAGE QUALITY
You will find that a combination is better than the other, but I can't give you a rule here. You have to try both combinations.

POST EDIT PHYSICAL CONSTRAINTS
Some teleconverters with protruding optics, like Canon's and Sigma's, will not allow you to stack them but in only one order. So if you are in this situation you can't do it in any other way.