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FORUMS Canon Cameras, Lenses & Accessories Canon EF and EF-S Lenses 
Thread started 24 Jun 2009 (Wednesday) 08:18
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2X TC and Various Lenses

 
phigment
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Jun 24, 2009 08:18 |  #1

I recently picked up a Tamron 2X non reporting TC. My intent is to use it with my 70-200 4L. After playing around with it I found some results that maybe some of you could explain.

First, I am using this on a 5DII.

1) 70-200 4L: Surprisingly AF works great. There are a couple misses, but I am pleased with how quick and accurate the lens focuses. Even in evening light it seems pretty quick.

2) Sigma 50 f/1.4: Now, I don't think I would use the 2X TC with this lens, but I tried it anyways. I thought that with the aperture being f/2.8 AF should have no problem. Quite the opposite. Without the TC, AF is quick and most of the time accurate.

With the TC AF hunts and jitters back and forth and only sometimes does it obtain proper focus. I've tried it in very bright light and that doesn't help. If I put the lens to manual focus, the focus confirm light works properly, but AF just doesn't want to work.

Any ideas why the 50mm f/1.4 is having trouble with the TC? I mean even at f/2.8 the high precision centre point should still be activated. I tried using the outer focus points and while still pretty bad I think they work a little better (this could be my imagination though).

Anyways, I thought some of you may know the answer or be interested in my observations.

I will try with my 17-40 4L tonight and see how AF works any better than the sigma.


A7R, Firin 20mm, CV 21/4, CV 40/1.4, 100ZE, 300 4LIS, Tamron 150-600, Jupiter 8, RX100 IV

  
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tekkie
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Jun 24, 2009 08:23 |  #2

I am not sure about the 2x but the canon 1.4 is not supposed to be used on lenses less than 135mm


Canon 1DMKII, 7D, 5DMKII, 1D MKII
Canon 500L, 100-400L
, 70-200 2.8L, 17-40L, 24-105L, 24mm 2.8,50mm 1.4, 85mm 1.8, 135mm 2.8 SF, 100mm Macro
Canon 430 & 580 flashes

  
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phigment
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Jun 24, 2009 08:42 |  #3

tekkie wrote in post #8165356 (external link)
I am not sure about the 2x but the canon 1.4 is not supposed to be used on lenses less than 135mm

Okay, but is that not due to physical limitations with the Canon TC? I would have thought that since there is no problem with the rear element on the sigma and the TC is non-reporting (even if it did report the the aperture would still be 2.8 ) that everything should be okay.

Is it possible that there is more than 2 stops of light being lost and the center AF point doesn't have enough light to work as a cross type?


A7R, Firin 20mm, CV 21/4, CV 40/1.4, 100ZE, 300 4LIS, Tamron 150-600, Jupiter 8, RX100 IV

  
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engrmariano
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Jun 24, 2009 08:55 |  #4

not sure about TC's will not work with FLs less than 135mm, but my Kenko 2X TC works fine on my 16-35L...


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gasrocks
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Jun 24, 2009 10:17 |  #5

Remember that TCs amplify everything - good and bad about a lens. So, depending on the quality of the lens, you may not want to see 2X.


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tekkie
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Jun 24, 2009 10:51 |  #6

phigment wrote in post #8165464 (external link)
Okay, but is that not due to physical limitations with the Canon TC? I would have thought that since there is no problem with the rear element on the sigma and the TC is non-reporting (even if it did report the the aperture would still be 2.8) that everything should be okay.

Is it possible that there is more than 2 stops of light being lost and the center AF point doesn't have enough light to work as a cross type?

I have no clue why ;) but if canon is saying not to use it there is probably a reason


Canon 1DMKII, 7D, 5DMKII, 1D MKII
Canon 500L, 100-400L
, 70-200 2.8L, 17-40L, 24-105L, 24mm 2.8,50mm 1.4, 85mm 1.8, 135mm 2.8 SF, 100mm Macro
Canon 430 & 580 flashes

  
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mspringfield
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Jun 24, 2009 14:15 |  #7

tekkie wrote in post #8166257 (external link)
I have no clue why ;) but if canon is saying not to use it there is probably a reason

It is because the front element of the 1.4x and 2x TC II stick out in front of the mount. The opening in Canon lenses shorter than the 135 will not allow the front mount on the TC to mate with the mount on the lens. Sigma, Tamron, or Kenko TCs do not have the same design on the front element. Also the original Canon TCs do not have it either so they will work.

Michael


Michael Springfield - Chattanooga, TN
Canon 1DsMkIII, Canon 1DsMkII, Canon 1DMkIII, Canon EOS M, Canon 28-70mm 2.8L, Canon 70-200mm 2.8L IS, Canon 100mm F/2, Canon 100mm F/2.8L IS Macro, Canon 135mm F/2L, Canon 200mm F/1.8L, Canon 300mm F/4L IS, Canon EF 1.4x II

  
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tekkie
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Jun 24, 2009 15:27 |  #8

yeah that could be it


Canon 1DMKII, 7D, 5DMKII, 1D MKII
Canon 500L, 100-400L
, 70-200 2.8L, 17-40L, 24-105L, 24mm 2.8,50mm 1.4, 85mm 1.8, 135mm 2.8 SF, 100mm Macro
Canon 430 & 580 flashes

  
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2X TC and Various Lenses
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