Do we still need a TC?

Started Nov 11, 2013 | Discussions thread
Anastigmat Forum Pro • Posts: 12,663
Re: Do we still need a TC?

Alastair Norcross wrote:

I've done a bit of research, and from what I can tell, it looks like the Pentax has the usual PD limitation (for a crop camera) to F5.6, which means it won't AF an F5.6 lens with a 2X teleconverter. You might be able to trick the camera into not realizing it has a converter. You can do that with Canons too, and achieve some kind of AF, but it tends to be slow and hunt a lot. The 1DX and 5DIII will PD AF with an F8 lens, but even they won't do it with F11. Were you thinking of live view AF? If you use live view, of course, you can AF with as slow a lens as you like, but live view AF is pretty slow. The fastest I know of is the new 70D, with its hybrid live view system.

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For most cameras, regardless of brand, the excess hunting with a f/5.6 lens and a 2x teleconverter will force most users to give up and focus manually.

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