kenko tele converter question

vanandjuanunited · 22 Jul 2009 at 17:15

thinking of buying one of these for my pentax k100d. Says auto focus works with lenses f4 or faster. I have o tamron 70-300 f4-5.6. Will autofocus work with this?
Thanks

Raikiri · 22 Jul 2009 at 17:16

No, with a 2x teleconverter your lens will become f8-f11.

D.P. · 22 Jul 2009 at 17:22

williamw11 said:
thinking of buying one of these for my pentax k100d. Says auto focus works with lenses f4 or faster. I have o tamron 70-300 f4-5.6. Will autofocus work with this?
Thanks

No, and the TCprobably wont even physically attach to the lens, and in anycase the image quality would be dire and the focus speed unbearable.

aztechnology · 23 Jul 2009 at 11:26

I have tried a generic 2x converter on a 70-200 F4 L on a 40D. It mostly hunts for focus. If you are happy with manual focus.

What camera you are using it on will determine whether you can use AF. More than likely you won't be able to, but you'll have to dig around for the AF specs for your pentax.

denyerec · 23 Jul 2009 at 12:03

The 1.4x is supposed to be optically pretty good, 2x usually eat so much light as to make life pretty rough unless you're starting out with an f2.8 lens.