Do we still need a TC?

Started Nov 11, 2013 | Discussions thread
Anastigmat
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Re: Do we still need a TC?
In reply to awaldram, Nov 11, 2013

awaldram wrote:

MightyMike wrote:

Alastair Norcross wrote:

awaldram wrote:

Anastigmat wrote:

If your lens is f/5.6, a 2x teleconverter requires manual focusing, Unless you focus correctly, you won't get a sharp image.

Only if you own a Canon, a Pentax will Auto focus an f5.6 + 2x converter with ease.

Really? A Pentax will perform phase-detect auto focus with a lens whose widest aperture is F11? I didn't know that. How fast is it?

Actually things have changed... It used to be (K10D to K-5) F8 with ease, F9 with little issue and F10 was pushing your luck, F10.7 only in the most extreme cases. When the K-5IIs came out F9 started to become a lot more difficult to focus... I don't think the K-3 has been fully tested for this yet.

K3 , 50-500 f6.7 + 2x converter

F 13.4 = no issue

Nothings changed as far as I can see maybe you need better quality converter ?

Sorry about subject matter but it's dark out and hand holding 1000mm Auto focusing indoors take some light.

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Alastair
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Mike from Canada
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Exactly, the light is the problem. If you have a bright light with good contrast like that a f5.6 lens and a 2x teleconverter will still autofocus. Point the same combination at a hawk sitting in a tree outdoors even when there is sunlight, and the autofocus will still hunt back and forth. Hawks are not like lamps.  They don't come with LED or tungsten bulbs. With a f5.6 lens, a 1.4x teleconverter will still allow autofocus in real world situations with real world subjects, but not a 2x.

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