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02-14-2012, 09:59 PM   #1
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AF 1.7 TC question

Just curious. How does the AF 1.7 TC work to focus manual focus lenses? Do you set the lens to infinitey and the TC element moves when focussing?

02-14-2012, 10:39 PM   #2
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No, you have to pre-focus the lens itself getting it within range of whatever you are focusing on and then the TC will take over to fine focus or fine tune and get it more exact. It may not sound very effective but I used one for a year with one of my telephoto lenses and really really liked it!! The element in the TC only has a small distance it can travel so that is why you have to prefocus the lens itself first.
There is a definate adjustment period to using it but once you warm up to it, you can get some great results. It does have some limitations too, in that it will only autofocus reliably with a good amount of light coming in and it should be used on a "fast" lens with an aperture of f4 or greater. You can get it to work around f5.6 but its going to be a crapshoot.
Search the other threads on the forum about the TC or Autofocus Adapter as it is actually named because there are many and there are 2 types of people in the world, the ones that like the 1.7X AFA and the ones that don't.

(patiently waiting for one from the other party to join the discussion )

Last edited by littledrawe; 02-14-2012 at 10:45 PM.
02-14-2012, 11:44 PM   #3
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littledrawe is correct when using long telephoto lenses but with shorter, normal lenses, prefocusing the lens to infinity will work. Then again, what's the point of using any TC with a normal lens, eh?
02-15-2012, 12:47 AM   #4
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Original Poster

Thanks for clearing this up. I probably won't get one unless it falls in my lap, but it is good for me to know how it works.

02-15-2012, 06:18 AM   #5
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It is also useful with macro lenses, as the TC will allow you to focus on shorter distances than on which the lens are focused. I use it very successfully with DFA50/2,8.
02-15-2012, 07:43 PM   #6
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I probably should have figured out by this time what the theoretical lens extension of the TC actually relates to, in terms of the focusing range. At some point, especially with up to a 50mm lens, it might just about give you full infinity to minimum focus, but clearly on a 300mm lens you don't get that.
02-15-2012, 09:26 PM   #7
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@ littledrawe (patiently waiting for one from the other party to join the discussion )

No detractors as yet, its a great little piece of glass, the new DA 1.4x TC is going to have to be good to compete. IMHO

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