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10-03-2008, 02:07 PM   #1
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Converting a Kenko 2x converter for SDM!?

I posted first part of this in another thread, but decided it deserves it's own thread (and don't want to hijack).

Some of us have got the Kenko 2x converter that appears to have the correct SDM contacts and are a bit sorry that it does not work with Pentax SDM lenses.

Observations:

1. The converter works well in screw driver mode with my screwdrive-only-lenses, even those slower than f2.8, though in this case with some hunting in dark situations. It does this on both K20D (has SDM) and *istDS (has not SDM).

2. The converter and the DA*50-135 autofocus with screwdrive on my *istDS and MZ-5 (tough of course in the later case I'm certainly missing the aperture ring!)

3. But when mounting the Kenko 2x converter and the DA*50-135 on the K20D the autofocus is dead! Not a sound, not a motion, not the smalest vibration. Screwdrive and SDM is both stone dead! In the viewfinder "MF" is visible despite that AF is on on both body and lens.

4. I have even tried to isolate the SDM contacts with a piece of plastic film in order to try to make the camera/lens believe it is just a screwdrive converter without the SDM contacts, and still it does not work! However, when doing this, even exposure functions breaks apart. Alternating numbers are flashing for the exposure time and aperture in the viewfinder and "MF" is now flashing, not a constant light as before. This implies that the SDM contacts are somehow involved in transferring information relevant for the exposure and not only providing the SDM engine with power !?

Hypothesis: Despite that contacts on the Kenko 2x look identical to the contacts on the Kenko 1.5x and Tamron 1.4x (that have been reported to work with SDM lenses) they are not SDM contacts, but power zoom contacts, which for some reason works differently.

But it is not a good hypothesis since it does not explain all observations.

Though I never had a power zoom, I understand it as the SDM use identical contacts as the contacts used for the power zoom. Right? But it appears it is not as simple, or? If the SDM/powerzoom contacts on the converter is just going straight through, why doesn't the SDM engage? If it is not, why doesn't the screwdrive engage even when I cover those contacts. Way strange. Anyone able to explain this to me?

I'm not going to buy any other over-priced third part converter now when the Pentax is around the corner, but my Kenko converter is on queue for some surgery... I wanna know what's inside, what's there that is not as it should be, and if there is something I could fix.

Anyone who have taken apart their fine working and over-priced Kenko 1.5x or Tamron 1.4x converter so we can compare what's inside?

By the way. I think I have seen converters on ebay claiming to work with SDM lenses which on the photos appear to have the SDM contacts but not the other 7 contacts on the mount. I don't want to try them, since having exposure functions without autofocus is still better than having autofocus with only manual exposure. But if they work with SDM, it could be that there is some combination of the signal in the SDM contacts and the signals in the other contacts that mess things up. Know its a long shot.


So that's so far. Now I could not help but picking up some tools yesterday and take that Kenko converter and...

10-03-2008, 02:45 PM   #2
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Douglas,
You may want to connect a multimeter accross the contacts using the ohm setting to see just what is connected to what. It can also tell you if there are other components inside by differences in resistance. A standard pass through would be a short and anything less could indicate circuitry present.

Dave

QuoteOriginally posted by Douglas_of_Sweden Quote
I posted first part of this in another thread, but decided it deserves it's own thread (and don't want to hijack).

Some of us have got the Kenko 2x converter that appears to have the correct SDM contacts and are a bit sorry that it does not work with Pentax SDM lenses.

Observations:

1. The converter works well in screw driver mode with my screwdrive-only-lenses, even those slower than f2.8, though in this case with some hunting in dark situations. It does this on both K20D (has SDM) and *istDS (has not SDM).

2. The converter and the DA*50-135 autofocus with screwdrive on my *istDS and MZ-5 (tough of course in the later case I'm certainly missing the aperture ring!)

3. But when mounting the Kenko 2x converter and the DA*50-135 on the K20D the autofocus is dead! Not a sound, not a motion, not the smalest vibration. Screwdrive and SDM is both stone dead! In the viewfinder "MF" is visible despite that AF is on on both body and lens.

4. I have even tried to isolate the SDM contacts with a piece of plastic film in order to try to make the camera/lens believe it is just a screwdrive converter without the SDM contacts, and still it does not work! However, when doing this, even exposure functions breaks apart. Alternating numbers are flashing for the exposure time and aperture in the viewfinder and "MF" is now flashing, not a constant light as before. This implies that the SDM contacts are somehow involved in transferring information relevant for the exposure and not only providing the SDM engine with power !?

Hypothesis: Despite that contacts on the Kenko 2x look identical to the contacts on the Kenko 1.5x and Tamron 1.4x (that have been reported to work with SDM lenses) they are not SDM contacts, but power zoom contacts, which for some reason works differently.

But it is not a good hypothesis since it does not explain all observations.

Though I never had a power zoom, I understand it as the SDM use identical contacts as the contacts used for the power zoom. Right? But it appears it is not as simple, or? If the SDM/powerzoom contacts on the converter is just going straight through, why doesn't the SDM engage? If it is not, why doesn't the screwdrive engage even when I cover those contacts. Way strange. Anyone able to explain this to me?

I'm not going to buy any other over-priced third part converter now when the Pentax is around the corner, but my Kenko converter is on queue for some surgery... I wanna know what's inside, what's there that is not as it should be, and if there is something I could fix.

Anyone who have taken apart their fine working and over-priced Kenko 1.5x or Tamron 1.4x converter so we can compare what's inside?

By the way. I think I have seen converters on ebay claiming to work with SDM lenses which on the photos appear to have the SDM contacts but not the other 7 contacts on the mount. I don't want to try them, since having exposure functions without autofocus is still better than having autofocus with only manual exposure. But if they work with SDM, it could be that there is some combination of the signal in the SDM contacts and the signals in the other contacts that mess things up. Know its a long shot.


So that's so far. Now I could not help but picking up some tools yesterday and take that Kenko converter and...
10-03-2008, 02:50 PM   #3
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If you do this, it is on your own risk. Taking appart lenses, especially a simple thing as a converter, is relatively easy. Putting them together is hard. Takes patience and steady fingers.

The Kenko converter is plastic, though all important pieces are metal. But not the best metal. Use good screwdrivers of a good fit when you take it apart. The screws that keep the bayonets in place were quite soft.
Be careful because there are plenty of loose pieces in there, including some very small springs. Work over a surface where you can find small pieces that goes their own way.

This is what it looks like after the first step:


In the piece to the right, the biggest one, the cylinder walls of the converter, you can still see the 7 electrical contacts that transfer lens information to the camera. On the blanket you see the 7 contacts from the other end of the converter. Note that one is slightly shorter, and that you must keep track of its position if you want to be able to make it work properly again. Note the small springs sitting on the contacts (upward in the photo). They get lose easily. Take care.

The MC4 and MC7 KA converters I have taken apart before, without any autofocus, there were similar contacts on both sides which were joint in the middle with one or two springs. They transferred any electrical signal straight through the converter. For KA lenses and cameras it was enough to let the converter connect every contact on the camera with the contacts/surface or plastic isolated surface on the lens mount. The construction here is not as simple. Something is in between!



Here I have turned the piece that was to the right in the first picture upside down and replaced the seven contacts (note the "gold" colored, it is the shorter one).
As you can see, they rest (on their springs) on an electronic circuit instead of connecting directly to the contacts on the other side. Another screwdriver and here we go...



Here is the bad guy! Each contact rest on a spring which rest on one of the electronic circuit contacts A to G. Then on the other side, the same thing again. So the circuit board are positions between two lines of springs. However, the signal does not go straight through any longer. The G position is the one Bojidar Dimitrov call the digital info contact. It transfer most of the info on aperture focal length, lens type, focus distance etc from the modern lenses to the modern cameras. The lenses also has a circuit inside it, sending all this info to the camera and receiving info (on as "secret" format).

But here Kenko have its own circuit which obviously tries to modify this signal. The only reason I can think of is that they have tried to make the converter modify the lens to camera signal considering focal length and aperture. Great idea! But it did not work! Instead the SDM lenses are totally dead considering autofocus.

Have any of the lucky owners taken a look in their Tamron 1.4x or Kenko 1.5x, converters that work with SDM? Is there also a circuit? Does these converters modify the aperture and focal length from the lens to the camera?

What to do now? Well I want this converter to do SDM on my DA*50-135 and I have some plans and options...

Last edited by Douglas_of_Sweden; 10-03-2008 at 03:03 PM.
10-03-2008, 04:53 PM   #4
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QuoteOriginally posted by Douglas_of_Sweden Quote
I posted first part of this in another thread, but decided it deserves it's own thread (and don't want to hijack).

2. The converter and the DA*50-135 autofocus with screwdrive on my *istDS and MZ-5 (tough of course in the later case I'm certainly missing the aperture ring!)
Douglas,

did I get you right that you are using the DA* 50-135 on a 35mm film camera? If yes, how is it? Is there much vignetting or lack of sharpness in the corners?

Forgive me my off-topic question, wasn't inteding to hijack your thread

Thanks!

10-03-2008, 09:38 PM   #5
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I do not have an SDM lens to test mine and I am reluctant to take it apart, but here are the things I know about the Kenko converters which might help you:

I have a Kenko Pz-AF 1.5x Teleplus SHQ. This one was manufactured long before Pentax introduced SDM, but it has the 2 contact inside the converter. Unless Kenko knew long before everyone else about SDM (which is very unlikely) they had another function, most likely it was for powerzoom.

There are 2 versions of this converter the 1.5x SHQ and the 1.4x Teleplus Pro 300 which might be similar to the tamron (more info here: [link][http://www.traumflieger.de/desktop/telekonverter/konvertertest2.php [/link]). Both are identical optically and both have 1.5x magnification.
The 1.5x SHQ transmits the aperture information directly to the camera: if you use an f4 lens and the 1.5x converter the widest aperture in the display is still 4 (this does not really matter since after metering the camera just has to know how many steps to stop down and not to which number).
The 1.4x Teleplus Pro 300 modifies the reading of the widest aperture and the correct widest aperture is displayed on the camera: for a f4 lens 4x1.4=5.6. This is also the reason why it is sold as an 1.4x converter, if it would be 1.5x the widest aperture indicated to the camera would be f6 for a f4 lens, and the camera would refuse to use autofocus.

My guess is that the chip you found in your converter is exactly for this function: calculating the correct aperture for the camera. Maybe it somehow confuses the SDM function since there are some calculation in between camera and lens. I wonder if it also changes the focal length transmitted to the camera, and if this is somehow misread and messes with SDM. If it is just transmitted through the shake reduction should not work right. Do you have a 'pro' converter? Maybe the cheaper non''pro' would work. Also try leaving the contact pin for the G position out when reassembling- if you are lucky it works.
10-03-2008, 10:06 PM   #6
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One could speculate that the 'G' contact transmits information related to SDM autofocus, and that the two 'powerzoom' contacts just supply power. Since Kenko's chip is older than SDM it cannot undertsnad and process the SDM related information. So SDM doesn't work.

If you bypass the chip it might work.
10-04-2008, 03:17 AM   #7
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QuoteOriginally posted by Big Dave Quote
Douglas,
You may want to connect a multimeter accross the contacts using the ohm setting to see just what is connected to what. It can also tell you if there are other components inside by differences in resistance. A standard pass through would be a short and anything less could indicate circuitry present.

Dave
That is an excellent suggestion, but I went a bit further than that already before your post. What I will probably do is to measure directly on the circuits.

But in some way this matter less, since I do not plan to fix the circuit. Changing an integrated circuit/chip is more or less impossible without very advanced knowledge and equipment. What I plan is to skip the chip entirely!
10-04-2008, 03:19 AM   #8
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QuoteOriginally posted by Noisychip Quote
Douglas,

did I get you right that you are using the DA* 50-135 on a 35mm film camera? If yes, how is it? Is there much vignetting or lack of sharpness in the corners?

Forgive me my off-topic question, wasn't inteding to hijack your thread

Thanks!
It was only because I wanted to test if the screwdrive AF or SMD AF activated with the converter and DA*50-135 on cameras with electronics of different generations. Hence I tried both my MZ-5 and the *istDS. I never took any pictures.

10-04-2008, 03:39 AM   #9
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QuoteOriginally posted by chse Quote
I do not have an SDM lens to test mine and I am reluctant to take it apart, but here are the things I know about the Kenko converters which might help you:

I have a Kenko Pz-AF 1.5x Teleplus SHQ. This one was manufactured long before Pentax introduced SDM, but it has the 2 contact inside the converter. Unless Kenko knew long before everyone else about SDM (which is very unlikely) they had another function, most likely it was for powerzoom.

There are 2 versions of this converter the 1.5x SHQ and the 1.4x Teleplus Pro 300 which might be similar to the tamron (more info here: [link][</title> <meta http-equiv="Content-Type" content="text/html; charset=windows-1252"> <meta http-equiv="Content-Language" content="de"> <meta name="GENERATOR" content="Microsoft FrontPage 5.0"> <meta name="ProgId" content="FrontPage.Editor.Document"> < [/link]). Both are identical optically and both have 1.5x magnification.
The 1.5x SHQ transmits the aperture information directly to the camera: if you use an f4 lens and the 1.5x converter the widest aperture in the display is still 4 (this does not really matter since after metering the camera just has to know how many steps to stop down and not to which number).
The 1.4x Teleplus Pro 300 modifies the reading of the widest aperture and the correct widest aperture is displayed on the camera: for a f4 lens 4x1.4=5.6. This is also the reason why it is sold as an 1.4x converter, if it would be 1.5x the widest aperture indicated to the camera would be f6 for a f4 lens, and the camera would refuse to use autofocus.

My guess is that the chip you found in your converter is exactly for this function: calculating the correct aperture for the camera. Maybe it somehow confuses the SDM function since there are some calculation in between camera and lens. I wonder if it also changes the focal length transmitted to the camera, and if this is somehow misread and messes with SDM. If it is just transmitted through the shake reduction should not work right. Do you have a 'pro' converter? Maybe the cheaper non''pro' would work. Also try leaving the contact pin for the G position out when reassembling- if you are lucky it works.
Thanks for a lot of interesting information!

First, I understand completely that you don't want to take it apart. It's a bad habit of mine since I took apart my dads clock when I was 5 years old (and never managed to put it together using all pieces ). But maybe if you have a multimeter, could you try Big Daves suggestion above and just test with the resistance meter (ohm) if the contacts goes straight through without obvious modification?

I don't know if the converter is a pro-version. It certainly does not feel very pro with its plastic hull I wasn't aware of that the older 1.4 pro version was available in K mount, because the present pro-versions are not.

In any case, I agree with you that the chip must be there to change the aperture read by the camera and the aperture setting sent to the lens. If one built it today, it should of course also change the focal length, continuosly, to help the SR (and I just assume Pentax new converter will do that...). But what about the time when the SDM contacts were power zoom contacts? Were the digital info contact (G in this converter) sending focal length already then? For what purpose before SR? I know so little about power zoom, so I would be most obliged if someone who have used and know more about the power zoom features could advice here.

Makes me thinking about something else I've been wondering, not directly related to this: What happens when you put a SDM lens on a power zoom camera? What happens when you put a power zoom lens on a SDM camera?
Does the SDM and the power zoom respectively engage?

As for your suggestion of leaving the G contact out, which is a good idea, I've already been working along that line, eliminating different contacts including that one, the others, the SDM contacts, the screw drive gear (don't want to risk to engage both SDM and screwdrive at the same time, might seriously harm the lens), eliminating one or all except one to see what happens. To give the whole picture I will make a separate post on this when I'm done trying all options.
10-04-2008, 03:54 AM   #10
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QuoteOriginally posted by Ole Quote
One could speculate that the 'G' contact transmits information related to SDM autofocus, and that the two 'powerzoom' contacts just supply power. Since Kenko's chip is older than SDM it cannot undertsnad and process the SDM related information. So SDM doesn't work.

If you bypass the chip it might work.
Yes, the G contact must be sending info on the autofocus, there is no other way to do it, unless...
The two power zoom/SDM contacts go straight through, they are not involved in the chip I found there. Forgot to write that. I think I read somewhere about the power zoom that the two contacts only gave power, no info. Can someone confirm that?
But what about the identical SDM contacts? Do they also only give power to the SDM engine, leaving the task of sending focal length etc to the G contact?

Then you have been reading my mind...but of course the final path should be quite obvious. When I'm done with the "contact elimination"-method, see reply to chse above, and if this does not result in some fantastic solution (I sort of don't expect that, just do it to understand), I will try to by pass the whole chip. Easiest way would be to just remove the circuit card with the chip and make the contacts go straight through. But I have already checked that the lost distance represented by the thickness of the card, is too large, the contacts and springs does not contact well. So it will take some construction work replacing either springs or contacts with longer ones or fitting a suitable new piece of metal in between the two springs on each contact. This will have to be done so the contacts still cannot short cut. What I hope to achieve then is a 2x converter that activate SDM. The drawback will be that 1) camera will have to correct for the wrong aperture, but that should not be difficult 2) the SR functions will work on the wrong focal length...don't know how to fix that, might just have to live with it. But honestly, I have low expectations. If I can get the SDM lens to autofocus on this converter even with the screw drive, I will be happy! The odd thing now is that it doesn't autofocus with any method.
10-04-2008, 10:48 AM   #11
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QuoteOriginally posted by Douglas_of_Sweden Quote
...
Makes me thinking about something else I've been wondering, not directly related to this: What happens when you put a SDM lens on a power zoom camera? What happens when you put a power zoom lens on a SDM camera?
Does the SDM and the power zoom respectively engage?
...
The basic function of the a Power Zoom (i.e. power zoom (!)) mounted on a K20D, K10D, etc. works.

Support of the advanced features was discontinued even on the later film cameras such as the ZX-5N.

We have explained the full set of features here:

Pentax Lens Power Zoom

The "G" contact probably played a role sending control information to the zoom motor and sending focal length information to the body.
10-04-2008, 11:46 AM   #12
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Kenko 1.5x teleconverter

i have Kenko 1.5x teleconverter
it dose not work with sdm lenses
i hope to try next week tamron teleconverter
10-04-2008, 11:55 AM   #13
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QuoteOriginally posted by Ole Quote
The basic function of the a Power Zoom (i.e. power zoom (!)) mounted on a K20D, K10D, etc. works.

Support of the advanced features was discontinued even on the later film cameras such as the ZX-5N.

We have explained the full set of features here:

Pentax Lens Power Zoom

The "G" contact probably played a role sending control information to the zoom motor and sending focal length information to the body.
You are correct, the G contact sends focal length information to the camera.

What every body is midding here is that while the cameras can read focal length data from all lenses, the data format has changed over time, therefore a teleconverter that is programmed to send data from an old KAF2 power zoom mount will not send data correctly from a newer mount lens, probably like the SDM lenses.

This TC does solve some other problems however with older lenses, and newer pentax bodies. By having a chip that translates correct apature information to the camera, the camera (specifically the K10and K20) will meter correctly with a TC installed. TCs that just pass through information have metering errors because the K10D itself has an inherent error in metering that requires knowledge of maximum apature to correct
10-04-2008, 12:47 PM   #14
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QuoteOriginally posted by Lowell Goudge Quote
...the K10D itself has an inherent error in metering that requires knowledge of maximum apature to correct
Lowell, could you elaborate on this statement; I've never heard about that before. Traditionally Pentax cameras have not needed information about the maximum aperture for other reason than being able to display the aperture value correctly (like for A lenses).
10-04-2008, 05:10 PM   #15
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I've heard about this, but also heard that the K20D has not this problem (and certainly I have not noticed any), so I'm counting still on being able to use the converter if I can bypass the chip.

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.
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