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10-27-2008, 05:06 PM   #31
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QuoteOriginally posted by Lowell Goudge Quote
In thinking back about the modification Douglas has done, to achieve AF with the HSM lenses, I can think of one thing to change.

I think he should leave the circuit board in place with the exception of the 7th pin (furthest from the locking pin). For that pin, he should carefully cut the traces and feed the 7th pin streight through.

Why do this? Simple, although the camera should not care about having the correct apature, the K10D and K20D do care. They use it to correct for a metering issue. therefore if the circuit is lecft in place to correct apature range (first 6 pins) but the lens focal length and distance are fed streight through the camera will meter better.
Well, it may be a good suggestion, but it is based on the assumption that the converter does something with the aperture range, in the case of the DA*50-135 changing the minima aperture from 2.8 to 5.6.

But as I mentioned further up the thread, it doesn't:
1) Happened to find the small one page "manual" of the converter stuffed down in the bottom of the tiny original (fake) leather bag which the converter came in. I quote from "3. Exposure mode": "However, the indicated aperture is different from the effective aperture (2 stops less than indicated)".
2) I can, unmodified version, get the camera to read f2.8 as the aperture. If the converter doubled the minima aperture to 5.6, it should not be possible. It should read f5.6 when I feed the lens/camera enough light, but never below 5.6.

Non the less, it measures fine, unmodified and modified: with the DA*50-135 as well as the A*85, A*135 and some other lenses. The problems above with exposure after the modification was due to a badly fitted mechanical aperture arm which prevented the lens from closing the aperture so that I always shot at full open or close to full open (something like ~f3.1) whatever the camera tried to shoot at. After I took it appart again and put it together again, it worked fine.

So to me it does not seam like the aperture range has anything to do with the problem we see here. Either we allow the chip to modify the 7th pin to something unknown, which makes both SDM and screwdrive to be dead, or we cut it off, and the camera believe it is a A-lens (which has not SDM and no screwdrive, and it of course doesn't engage any autofocus). This was tried with and without the other six pins, with and without the SDM/power zoom contacts, with and without the screwdrive gear. Without the 6 A-generation pins, it treats the lens as a manual pre-A-lens (which never had autofocus...don't bring up MEF now, OK) with the same result. When the chip was skipped for all 7 contacts, SDM works in principle but not in practice because it hunts (because it is too little light left?).

As it appears that the six aperture range pins are not modified by the chip, it must be that the chip use their info to help modify the signal in the 7th data pin. But whatever it does the lens speak greak (powerzoom), while the camera speak latin (SDM). Not the best simile, I know, since without the chip and all pins in place they do speak some sort of latin both of them. It is when Kenko modifies the signal that it fails. Does anyone knows if the communication protocoll of the 7th pin has been published anywhere (powerzoom or SDM version)?

I might try to do what you suggest, but can't right now see how it would help. Except that it might validate my assumption above.

I have other 2x converters. The option to try to make the first-ever-on-this-planet-SDM-extension-tube is getting more tempting. I've already checked earlier this past summer that the DA*50-135 makes a nice macro combo with an automatic extension tube. The optics however are sitting where it is very firmly. Does not want to move a micrometer. Don't want to go over to the hammer+screwdrive method since it is a fairly good piece of optics...
Anyone who has removed the optics from a Kenko converter before?

After this thread I assume no one will ever want to buy a converter, or even a lens, from me again. Some might not even want to sell any to me!

02-08-2009, 11:36 PM   #32
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interesting thread indeed, Douglas.

I also have a Pz-AF 2x Teleplus MC7 like you and i wonder if i can use it with a new Sigma 150-500 HSM or a Sigma 120-400 HSM ??? (to extent the reach to 300-1000 or 240-800, wow ) Did you have any chance to test the TC on this kind of lens (i mean the HSM)
02-09-2009, 07:17 AM   #33
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QuoteOriginally posted by Douglas_of_Sweden Quote
Sorry, did not get to finnishe the tests today either. Had to prepare the garden for the winter. Autumn is in its prime here. But tomorrow is supposed to be rain and hard wind, so perhaps I can lurk at home trying to do those tests.
Douglas, thank you for your work and your superb reporting, illustration, and thoughtful discussion of it. It is among the best illustrated discussions I've ever seen, including professionally produced tutorials. You are gifted in this capability.

Please don't keep your light under a bushel.

04-11-2009, 10:51 AM   #34
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I just purchased a brand new K20D with a Pentax 16-45 lens. I also just purchased Teleconverter 2X KAX MACRO TELEPLUS MC 7 and now finding that it does NOT AF (Auto-Focus). My question is whether it should as the seller claimed it did. I paid aroung $200. for it and now wonding how much of a deal it really was. Is ther any 2X Telecoverter (TC) that will AF with a K20D?

Tom Cerbo, Clearwater FL

04-11-2009, 11:46 AM   #35
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I think (correct me if i'm wrong) the KAX does not keep AF ability, can you post some pictures of the TC???

for AF teleconverter, you can have them from Ebay, B&H, Adorama, etc, price should be from $120 to $180, Kenko and Tamron are popular ones
04-12-2009, 09:50 AM   #36
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QuoteOriginally posted by TCerbo Quote
I just purchased a brand new K20D with a Pentax 16-45 lens. I also just purchased Teleconverter 2X KAX MACRO TELEPLUS MC 7 and now finding that it does NOT AF (Auto-Focus). My question is whether it should as the seller claimed it did. I paid aroung $200. for it and now wonding how much of a deal it really was. Is ther any 2X Telecoverter (TC) that will AF with a K20D?

Tom Cerbo, Clearwater FL
The macro version is a manual focus tc. The Kenko 2x Teleplus MC7 AF DG should autofocus with your lens. It works on the f*300mm f4.5.
07-21-2009, 03:35 PM   #37
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Douglas, any news on the 2x teleconverter working with screw on sdm lens ?

I have one Tamron 2x Pz-AF BBAR MC7 (same thing as kenko I think) that works as it's supposed to with lens that are not SDM.

Now I have DA*300 and was wondering if it's possible to use it with SDM or screw.

Thanks in Advance

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