[mikeSF]

As long as you have the Pentax body in MF mode, the only force slowing down your MF focus of the Tamron lens will be the little shaft extension in the teleconverter. You can test how much friction it adds by holding just the teleconverter in your hand and turning the little screw-drive extension on the side that would attach to the lens with your fingers, it should turn very easily. (I suppose it's possible the shaft in your teleconverter is adding an undue amount of drag due to some sort of alignment problem, and that could be one way to find out.)

The resistance (in MF mode with clutch disengaged) with the TC on is a scratchy, grinding type of resistance; it is not the same as when AF is engaged, but there is a turning gear type of action occuring. It is such that fine focusing is not smooth due to the resistance being uneven.

I did examine the TC by itself and turn the screw shaft and it has virtually no resistance, at least nothing similar to that which I get with the lens attached to the TC. I also inspected the screw drive tip on the camera mount itself and it does indeed retract when the MF switch is selected.

I am now quite confused at your response since the drag is quite detectable and is accompanied by a scratching or gearing sound, very different from what you have described.

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Last edited by mikeSF; 06-26-2012 at 05:25 PM.

[nater]

The resistance (in MF mode with clutch disengaged) with the TC on is a scratchy, grinding type of resistance; it is not the same as when AF is engaged, but there is a turning gear type of action occuring. It is such that fine focusing is not smooth due to the resistance being uneven.

I did examine the TC by itself and turn the screw shaft and it has virtually no resistance, at least nothing similar to that which I get with the lens attached to the TC. I also inspected the screw drive tip on the camera mount itself and it does indeed retract when the MF switch is selected.

I am now quite confused at your response since the drag is quite detectable and is accompanied by a scratching or gearing sound, very different from what you have described.

I hear extra noise with a teleconverter attached to an AF lens and I manually focus the lens too. I just think I've never been that concerned with it. If you look at the RPMs that the shaft performs when you focus a lens by hand, it's a lot, so I can't say I'm entirely surprised... I do wish it was quieter, and more even - the unevenness would definitely bug me if I was doing more manual focus with that combo. I'm just not sure how worried you need to be... whatever gearing in the lens surely is strong enough to cope with whatever extra bit of friction that little teleconverter shaft extension is throwing into the mix. Whatever lens 'micro motor' is in place is probably more of a torque converter anyway, since screw drive lenses don't get electrical power from the camera body (unless it's a Pentax Power Zoom lens, a relatively short-lived line).

[jpzk]

beware the Tamron F 1.4x Pz AF MC4, as it is not recommended for use with the 70-200/2,8. I have both and it does not allow the AF motor to disengage, so maual focusing drags the gears.

Tamron cust service says:
"The teleconverter is not compatible with the 70-200 F/2.8 lens and we cannot provide support for its use. I would recommend discontinuing use of the teleconverter with that lens as they are not compatible. "


I have since heard someone say it is possible to simply hold the lens release button (if you still have one, lol) to temporarily disengage the gears for manual focusing. I have not tried this but will do so shortly and report back.

As for optics, i do like the results from the Tamron F but will keep looking for another TC that is fully compatible with the lens.

Ahhh .... I should have seen this before!
I thought this was THE best match but it sure isn't!
Thanks for bringing me back on course.

Cheers.

JP

[jpzk]

I am curious why you say they are a match as Tamron does not recommend they be used together.

Yeah Mike ... I just replied to this in a previous post.

I was "told" that it was a great match .... sorry, I never saw the warning by Tamron though.

Again, thanks for bringing me back to my senses!

JP

[dmort]

I'd like to suggest to the OP that instead of looking at the tamron to look at the sigma version of the 70-200mm as there are 1.4 and 2x teleconverters listed as compatible with the APO 70-200mm F2.8 EX DG / HSM and the APO 70-200mm F2.8 EX / HSM.

[larshalvar]

Even though the thread escalated a little bit I am grateful for all the replies. and thanks to dmort who gave me a easy but good alternative, unfortunately a little bit more expensive too

[dmort]

Look around online though, I find that since sigma has been making that sort of lens in a pentax mount for a while, they crop up on ebay, and here in the marketplace more frequently than you'd expect. Also, check KEH.com, bandh used department, and adorama used department. Variations on the 70-200mm come up every now in then, although, admittedly, I have rarely seen the TC's come up. You should also keep your eyes open for a 50-150 f2.8 b/c paired with the 2x tc, you get comparable range as you would with the 70-200mm paired with the 1.4. The 70-200mm + the 1.4 would still be faster though...

[jpzk]

Resurecting this thread:

Because I am always confused when I read long dicussions, I am going back a bit to some previous discussion about using the Pentax F 1.7x adapter with the Tamron 70-200/2.8 ...

Is this lens + adapter a good solution then?
If so, how would the setup be: lens on MF and camera also?

I'd like to give this a try since I have both the Tamron lens and this 1.7x adapter.

Thanks.

JP

[pacerr]

Listen to Nater.

I gave up tryin' to say that a LONG time ago 'cause it was a voice in the wilderness - without an echo.

The mechanical and electric properties of the AF mechanism, the lenses and the TC's are actually easy to understand once you give up the wishful thinkin' that there's a magic solution.

Three rules:

- Only use a TC on the LONGEST, BEST LENS AVAILABLE AT THE TIME. Testing IS necessary - i.e., TC vs. crop.

- Then accept the results as bein' the very best you could possible achieve with the gear available at that specific point in time. If you've made the wrong choice, accept it; and then . . .

- Buy the longest GOOD tele lens you can afford and/or upgrade when you can if you're not happy.

Ain't no free lunch. A TC's a compromise, not a solution! Be thankful you've got it (when you believe you're better off usin' it) and understand the trade-offs involved - those of both convenience and economics.

(Consider this: a REALLY GOOD TC's nothing more than the 500mm/f5.6 you can't afford - or haven't yet learned to use well. An' the cheap one's not gonna be any better than the TC+lens you already have.)

H2