[fwcetus]

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.

Huh ???

I think it is the ~reverse~ (at least that's ~my~ experience) - first you have to have the lens focused manually "in the ballpark" (i.e., not racked way out or way in, etc.), and then, when shooting, the F 1.7x AFA will snap the lens-AFA combination into focus. In practice, unless you're doing some close-focus work, leaving the mf lens itself focused at a little closer than infinity will allow the AFA to snap the combination into focus time after time on objects at at least a moderate distance. (For close focusing, of course the lens has to be "pre-focused" a lot closer to start with.) In any event, I have ~never~ had to "manually lock it in".

[fwcetus]

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

Exactly correct in your assumption - the focus screw moves glass around inside the TC. Clever!

[Mike.P®]

I have one and it works really well with my A* 300mm f2.8 .. giving me a 500mm f5.6 with semi AF. It also works well with my F* 300mm f4.5 reporting 500mm f8.

These were taken with it and the F* 300mm f4.5, the moon shot recently got chosen for the Pentax gallery.

[fwcetus]

Here are a few pix taken on a "walkaround Newport Rhode Island afternoon" with the Tokina AT-X 90/2.5 Macro mounted on a Pentax F 1.7X Autofocus Adapter (making for an "AutoBokina" - <g>), showing the AFA's use at infinity and at closer focus distances.

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Last edited by fwcetus; 04-29-2009 at 11:00 AM.

[D W]

Yes it even works with M42, P645 P67 and other lenses adapted to K mount.

[Canada_Rockies]

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

Yes, the converter has the autofocus (screw drive of course) mechanism built in. It does not have a long enough throw to completely focus a manual focus lens, but it will fine tune focus. Pentax rated it very conservatively, I think someone said f/2 or faster, but it will work with slower lenses.

one more question:
Does it work for instance with a M42 lens?

I am not certain about this. I don't have my adaptor any more, I sold it off to a fellow Pentaxian 20 years ago. The adaptor would have to go on the front of the converter. The narrower throat of the M42 lenses might make it non workable as an AF converter, but it is a splendid converter optically.

[cooldude14es]

Yes, at first it sounds strange, a manual lens becoming AF?? but thats it!!

I tested it together with an A50mm f1.7, it was really fast focusing, and no manual focus was needed, it just went from infinity to close distances like any other AF lens... sounds weird but it was awesome.

But the limit is on f5.6 or slower lenses... you wont get AF on them, that was my experience.

[Marc Sabatella]

I continue to kick myself for passing up on one of these when I saw it in a camera store a few years ago - before I had any clue what it was. I think it was selling for $150.

[hinman]

Pentax-F 1.7x AF TC is my most favorite TC. It works best with 'A' lens that are manual focus as it magically transforms a MF lens into partial AF. As others have mentioned, you have to manual focus first to the close proximity of targeting focus point and the AF in the TC will kick in and lock on target for you. Bokeh and color is not degraded much in my use with several lens from the 50mm, and a bunch of tele-primes in 200mm and 300mm.

Pentax A 50mm f/1.7 + Pentax-F 1.7x AF TC

It also works with M42 lens provided when the electrical contacts are made between the TC and the m42 mount. I have used aluminum foil for the assistance before and it can work with my 300mm tele-lens. On M42 lens, it is harder to focus due to the nature of diaphragm closing down in stop-down aperture, I usually focus first in wider aperture and stop-down right before shutter.

Photosniper Tair-3 PhS 300mm f/4.5 + Pentax-F 1.7x AF TC

Using foil to assist electrical contacts between TC
and M42 lens

And it works with AF lens, but you have to get used to manual focus first.

Pentax F* 300mm f/2.8 + Pentax-F 1.7x AF TC

AF.C but I have SR ON

1/1000 sec, f/8.0, 510mm, hand-held, iso 640, +0.3 Ev







I missed the framing




I missed the framing
but I cropped to see lesser error

Thanks,
Hin

[Adnan EROL]

Yes it even works with M42, P645 P67 and other lenses adapted to K mount.

good news for fast oldies ?

[Adnan EROL]

I have tested my Pentax-A TC, it didn't convert my manuel lens into AF one.
Sure I was not expecting anything, since it is not AF either. Just to give it a chance.

Then I took my Kenko Pz-AF TC, nope it is hopeless too.
Now, I'm waiting for a SDM lens to test with it.

Pz contacts are SDM compatible, isn't it?

[dopeytree]

$348.50 isn't that a bit steep?

[G_Money]

$348.50 isn't that a bit steep?

Well, there's one in the marketplace right now that started out at $300 and has come down to $275 for cosmetic reasons. Two sold on eBay in the U.K. for $300 US, give or take. The jinfinance eBay link is for a brand new one. I don't think it's outrageously priced. I wish Pentax would speed up development on that SDM compatible TC piece of vaporware, I'd like to see their SRP on that.

[Peter Zack]

Anything under $400 is a good price for this TC. It works very well and holds IQ. As for PZ cameras and SDM. Nope, cameras like the PZ-1p were not designed for SDM. the first cameras with SDM were K series starting with K100D super I think.

[Canada_Rockies]

Anything under $400 is a good price for this TC. It works very well and holds IQ. As for PZ cameras and SDM. Nope, cameras like the PZ-1p were not designed for SDM. the first cameras with SDM were K series starting with K100D super I think.

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.