get autofocus capability for your manual lenses! - Page 3

*F16* · 04-29-2009, 07:23 PM

get autofocus capability for your manual lenses!

Buy a Contax AX

I wonder how many mm of travel the optics in this TC have, I can't imagine it has room for much travel. Obviously the longer the travel, the more useful it becomes as it would require less fine tuning to get into AFing range.

**Damn Brit** · 04-29-2009, 09:49 PM

Originally Posted by Canada_Rockies

Thanks. What had I done wrong?

For some reason, the URL got repeated when you added it.

simico · 04-30-2009, 01:21 AM

Thanks for the info, interesting stuff. I always learn something new

ftpaddict · 04-30-2009, 01:26 AM

I've known about it for years; I'm surprised you've never found any mention of it here on the forums.

Ben_Edict · 04-30-2009, 02:05 AM

Originally Posted by MrApollinax

There are a bunch of people on here that report that it will get you close to focus but you will need to manually lock it in.

The other way round. You set manual focus roughly and the fine focusing will be done by the AF adaptor.

Ben

Ben_Edict · 04-30-2009, 02:08 AM

Originally Posted by simico

I don't understand this... a pure MF lens doesn't have any built-in mechanics for AF, the only way to focus is to turn the focusing ring with your hand. How can a TC make it AF?? Or is it that the TC have some moving optical element used for focusing?
Enlighten me please

The Pentax AF adapter has internal focusing, which is driven by the standard AF screw driver mechanism. To preserve images quality (and the IQ of that adapter is very good), the focus travel is limited, which necessitates the manual rough focusing of the lenses.

Ben

Adnan EROL · 04-30-2009, 11:18 AM

Originally Posted by Canada_Rockies

Peter, I think the poster was asking if a converter with the Pz contacts would support SDM, which uses the same pair of contacts. Today's reading in the forums lead me to believe that the answer is "Maybe". It seems some do and some don't.

Yes, I mean that

any tester? Which do? which don't?

Ben_Edict · 04-30-2009, 01:10 PM

Originally Posted by Adnan EROL

Yes, I mean that

any tester? Which do? which don't?

If you search for the Tamron 1.4x tc and the Kenko 1.5x tc ion the forum Search, you will find a very recent thread (only last week, if I remember rightly), which clarifies which version of these tcs supports SDM.

Ben

*Canada_Rockies* · 04-30-2009, 01:37 PM

I think this thread might help.

Teleconverter for DA* lenses

Originally Posted by Adnan EROL

Yes, I mean that

any tester? Which do? which don't?

Adnan EROL · 04-30-2009, 01:40 PM

Thanks, I've got it:
focus hunts like crazy

*Canada_Rockies* · 04-30-2009, 04:39 PM

Originally Posted by Adnan EROL

Thanks, I've got it:
focus hunts like crazy

That's the price you pay for the loss of 1, 1.5 or 2 stops of lens speed. AF works on bright lenses, and sometimes on dark ones. I have actually achieved auto focus with the 1.7X AF on the M 400/5.6. This is not something I expected, frankly.

vietlh81 · 05-01-2009, 03:00 AM

Originally Posted by Adnan EROL

Thanks, I've got it:
focus hunts like crazy

AFAIK, the slowest aperture works well on Pentax is f/6.3 (the Tammy one). It means that, if you combine use this TC, you must use the lens faster than 6.3/1.7 = 3.7.
In fact, my TC works quite well with f/4. For the faster lenses, AF speed is very fast.

I like it because combining with 50mm lenses, I have a 85mm lens, ideal for the portrait.

Now, I have a new Pen-kor lens

(Thanks to Pentax)

Lowell Goudge · 05-01-2009, 06:08 AM

Originally Posted by vietlh81

AFAIK, the slowest aperture works well on Pentax is f/6.3 (the Tammy one). It means that, if you combine use this TC, you must use the lens faster than 6.3/1.7 = 3.7.
In fact, my TC works quite well with f/4. For the faster lenses, AF speed is very fast.

I like it because combining with 50mm lenses, I have a 85mm lens, ideal for the portrait.

Now, I have a new Pen-kor lens (Thanks to Pentax)

I believe you are wrong here.

I have used the 1.7x AF TC on pentax AF bodies since my PZ-1. although the adaptor manual states F2,8 or faster, it has always worked for me on F4 lenses. I have 2 different F4 lenses, my SMC-M100F4 macro and my SMC300F4.

Also i believe if you look at all AF lenses, they top out at F6.7 or F6.8 depending on how they market them, not F6.3, because that is the limit of reliable AF

F4 x 1.7 is F6.8

one additional point I discovered with the AF TC, and it is only because I now have my first KA mount lens, is that the TC corrects for apature when mounted to the KA lens. An F1.4 lens shows as F2.8 in the viewfinder.

*F16* · 05-01-2009, 08:27 PM

It just depends on the camera and lighting conditions, and when using a TC some will have a more negative impact on AF than others. Take a lens rated at 5.6 and try to AF in a dim interior room and chances are decent that AF will struggle. Take the same lens out on a sunny day and it will behave much differently. You can get a lens with the equivalent of F8 or even F11 to AF under ideal conditions. The rough conventional number is somewhere between F5.6 and F8, the reality is that there is no hard number, it will just depend on the circumstances.

*jensm* · 05-03-2009, 02:18 PM

Just won an auction for one of these minutes ago (sorry if it was over another forum member). Got carried away...

Weill, I'm looking forward to trying it out with my K200/2.5, should turn it into a 340/4,25 which would be none too shabby :-)