50-135mm /f2.8 with AF1.7xTC

Just been outside with this combo. Wide open, hand held. Focus is FAST!!!!





Very shallow DOF. I like this combination.

C&C welcome

Regards

are you saying that focus is fast becauyse the TC bypasses the SDM focussing and therefore uses the in-camera AF motor?

does it make it much faster than the lens on its own?

what TC is this you're talking about, is it the Pentax version?

SDM is off as the Pentax AFTC is screw drive. Lens is pre-focused manually to "some where near" and the AF TC does the rest. K7 was indicating f4 due to two stop loss.

Zoom is still OK to use.

Regards

right, but you don't have to 'pre-focused manually to "some where near" ' - right?

I mean, does the screw drive not work normally? does the AF hunt more than the usual?

Yes Nathan, you have to pre-focus manually. The T'C can't cope with the full focus range of every lens ever produced. So some work (not much) has to be done to help the AF system get somewhere close.

Only just started to use this TC and the pre-manual focus is only as near as slightly recognisable subject, the TC then snaps it into focus. It does not hunt.

I will do some more shots at smaller apertures tomorrow to see how the IQ is. The extra reach of the 1.7x is very useful.

Regards

Very interesting, i would have thought that the AF would be able to cope with the full focus range.

But good to know!

#2 I like!! Very nice

Taps again at f/8. Apologies for error on previous post as f/4 was f/4.5




Better DOF as expected.

Then did this...




Regards

I'd always assumed that AF teleconverters worked by (the user) setting the lens to infinity, then the TC doing all the work itself. Interesting to know - not that I'm ever likely to find a Pentax AFTC for sale!

Something about the taps I like in both groups.
Interesting to the see the 1.7x TC working well with the 50-135.
Do you have the 60-250 and have you tried the x1.7 with it?

Don't have the 60-250.

Regards