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

General info about AF on Canon's dSLR.

http://www.usa.canon.c​om …tArticleAct&art​icleID=266

All xxD and 5D series. Loose auto focus with lenses f/8 and slower (@ f8+ not the camera aperture).

All xD series loose auto focus with lenses f/11 and slower (@f11+ not the camera aperture). It will also auto focus using center AF points.

When using T-Con 1.4 you loose a stop, when using TCON 2.x you loose two stops.

Keep also in mind that IQ sufers a great deal the more TCON are used and the lens AF speed will also decrease.

200Lf/2 + TCON 1.4 = 280L f/2.8 All Canon dSLR will AF.
200L f/2 + TCON 2.0 = 400L f/4 All Canon dSLR will AF.
200 f/2 +TCON 2.0 + TCON 2.0 = 800L f/8 xD and 5d will NOT autofocus, but 1D series will using center AF points.
200 f/2 +TCON 2.0 + TCON 2.0 + TCON 1.4 = 1120mmL f/11 none of Cano's dSLR will autofocus. Must use manual.

100-400L + TCON 1.4 = 140-560L f8 xxD and 5d will NOT autofocus, but 1D series will.
100-400L + TCON 2.x = 200-800L f11 none of Cano's dSLR will autofocus. Must use manual focus.

800L + TCON 1.4 = 1120mmL f/8 xxD and 5d will NOT autofocus, but 1D series will using center AF points.
800L + TCON 2x = 1600mmL f/11 none of Cano's dSLR will autofocus. Must use manual.

As far as I know , he canons will only allow full auo on full frame Canons .

Sorry 'bout that - post above mine explains better , but I read my emails top to bottom .

silvex wrote in post #9592232
General info about AF on Canon's dSLR.

All xxD and 5D series. Loose auto focus with lenses f/5.6 and slower.

All xD series loose auto focus with lenses f/8 and slower. It will also auto focus using center AF points.

Not quite right!...they do not LOSE autofocus at the f/stops stated, they MAINTAIN autofocus at those f/stops and lose them if the body thinks the lens is slower than the values stated.

Not sure if this has been posted, but the 1.4x Sigma TC will not connect to the Bigma. That sounds like a Sigma stigma to me. They can't build a 1.4x that connects to their own lens?

Wilt wrote in post #9595426
Not quite right!...they do not LOSE autofocus at the f/stops stated, they MAINTAIN autofocus at those f/stops and lose them if the body thinks the lens is slower than the values stated.

http://www.usa.canon.c​om/app/pdf/lens/EFLens​Chart.pdf

zoom to the right for the extender(s) tables.

http://www.bhphotovide​o.com …ts/canon1_4xExt​ender.html

silvex wrote in post #9597205
http://www.usa.canon.c​om/app/pdf/lens/EFLens​Chart.pdf

zoom to the right for the extender(s) tables.

http://www.bhphotovide​o.com …ts/canon1_4xExt​ender.html

Notice the 70-200mm f/4 (I have one)...it shows AF function (circle) at f/5.6, not an 'X' in that column. My 70-200mm f/4 IS autofocuses quite nicely with either mounted,an Canon 1.4 or a Kenko 1.4 (I own both), making it an f/5.6 lens. However it does not show up as functional with the 2x extender, as it would be an f/8 lens with that combination.


Borrowed from the Sticky on the POTN lens forum https://photography-on-the.net ….php?p=284148&p​ostcount=1

"Extender EF 1.4x II
This tele extender can be used with fixed focal length lenses 135mm and longer (except the 135mm f/2.8 Softfocus lens), and the EF 70-200 f/2.8L, 70-200 f/2.8L IS, 70-200 f/4.0L, and 100-400 f/4.5-5.6L IS zoom lenses. It multiplies its focal length 1.4x. Effective aperture is reduced by one f-stop; autofocus is possible on any EOS camera when combined with a lens having an f/4 or faster maximum aperture."

And when I mount both the Canon and Kenko telextenders on the 70-200mm f/4 IS lens, the body thinks (wrongly) that the lens is f/5.6 and it will TRY to autofocus, but it does not succeed especially if changing from close to far away (or vice versa)...if I manually focus it so it is relatively in the right range, the AF can work. Undependable results.

I took my XTI and 35-350 to KEBBLE AND Shu-- in Palo Alto - They had the canon 1.4 and 2 , the Sigma 1.5 ? and the kenko 3 . All tried to focus but started hunting .
This was 2 years ago so maybe now they work . It was done in shop under flourence lights .

35-350...f/3.5 to f/5.6 with a 1.4 teleconvertor becomes an f/5.0-f/8.0 lens. At f/8.0 the camera should stop trying to AF. From f/5.6 to less than f/8, it should try to focus (which it did) but it might not succeed (which is why Canon disables AF functionality in the non-1D bodies with f/8 lenses)

Thanks , I want the 100-400 , but the new 100 macro w / IS is about the same price - but then they came out with the T2i -- decesions - sorry 'bout hijacking post .

I corrected my entry. I meant to say f8/f11 and slower

Some question that I have then..
If you are set on a 1.4x TC (to be used on Canon 70-200/4 and/or 100-400).

a) Canon 1.4x II
b) Kenko 1.4x PRO 300
c) Kenko 1.4x DGX

Which one would give the best result, pros/cons?

Candersson wrote in post #9603484
Some question that I have then..
If you are set on a 1.4x TC (to be used on Canon 70-200/4 and/or 100-400).

a) Canon 1.4x II
b) Kenko 1.4x PRO 300
c) Kenko 1.4x DGX

Which one would give the best result, pros/cons?

No use experience with the DGX, which is a budget level product.

According to testing I had done the 70-200 f/4 non-IS, the Canon 1.4x-II teleconvertor is better at center, the Kenko Pro DG is better at edge. Both differences are quite subtle.

The Kenko will pair up with more lenses, because the Canon front element protrudes and prevents it from being used with 100mm lens, for example.

Wilt wrote in post #9603778
No use experience with the DGX, which is a budget level product.

According to testing I had done the 70-200 f/4 non-IS, the Canon 1.4x-II teleconvertor is better at center, the Kenko Pro DG is better at edge. Both differences are quite subtle.

The Kenko will pair up with more lenses, because the Canon front element protrudes and prevents it from being used with 100mm lens, for example.

That is interesting Wilt, I had the opposite with the 200/2.8 and 300/4 IS.

Canon better on edge and the kenko sometimes better in the centre (this is on APS-C), have to say the difference was not great in the centre but larger on the edge and corner, generally I would recommend the Canon based on my results.

example SRF plots for the 200/2.8

Thanks guys! Much appreciated
I've have found and read some more tests and have also seen the comment about edge/center differences, although very small. Just as you mention.
I'm leaning towards the Canon 1.4x II ---> next stop B&H