Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
10-05-2008, 06:50 AM   #16
Pentaxian
Lowell Goudge's Avatar

Join Date: Jan 2007
Location: Toronto
Photos: Gallery | Albums
Posts: 15,312
QuoteOriginally posted by Ole Quote
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).
check this post

https://www.pentaxforums.com/forums/241716-post69.html

the focusing screen causes an error as a function of maximum apature.

I believe Pentax corrected this by using maximum apature information of the lens, but on K mount's they don't know this data, and as a result the green button metering causes all sorts of problems.

swapping out the K10D screen for the *istD screen corrects this problem, but will cause a problem with "A" series lenses, because of the built in correction curve. As a result, if you change screens on the K10D you may get better manual metering but each "A" lens you have will need a constant correction factor applied.

the same issue exists with a teleconverter that just passes lens data through. My sigma 70-200F2.8 needs -1 stop for the 1.4x and -1.5 stops for the 2x TC to compensate for the error in metering.

10-05-2008, 08:37 AM   #17
Ole
Administrator
Ole's Avatar

Join Date: Sep 2006
Location: Copenhagen, Denmark
Photos: Gallery | Albums
Posts: 3,783
QuoteOriginally posted by Lowell Goudge Quote
check this post

https://www.pentaxforums.com/forums/241716-post69.html

the focusing screen causes an error as a function of maximum apature.

I believe Pentax corrected this by using maximum apature information of the lens, but on K mount's they don't know this data, and as a result the green button metering causes all sorts of problems.

swapping out the K10D screen for the *istD screen corrects this problem, but will cause a problem with "A" series lenses, because of the built in correction curve. As a result, if you change screens on the K10D you may get better manual metering but each "A" lens you have will need a constant correction factor applied.

the same issue exists with a teleconverter that just passes lens data through. My sigma 70-200F2.8 needs -1 stop for the 1.4x and -1.5 stops for the 2x TC to compensate for the error in metering.
Thanks Lowell, I remember your graph (and henceforth keep my *istD!) but wasn't aware of the alleged fix based om max. aperture reading for A lenses.
10-09-2008, 07:19 AM   #18
Site Supporter
Douglas_of_Sweden's Avatar

Join Date: Apr 2008
Location: Stockholm
Photos: Gallery
Posts: 3,347
Original Poster
QuoteOriginally posted by koper Quote
i have Kenko 1.5x teleconverter
it dose not work with sdm lenses
i hope to try next week tamron teleconverter
There have been people reporting that their Kenko 1.5x converter works with SDM lenses, but appears as it hunts more than the tamron 1.4x.
Presumably there are different versions of the Kenko converter. Perhaps yours has the same generation of chip as mine 2x. But I never heard of a Kenko 2x converter that works on SDM lenses.
10-14-2008, 04:54 PM   #19
Site Supporter
Douglas_of_Sweden's Avatar

Join Date: Apr 2008
Location: Stockholm
Photos: Gallery
Posts: 3,347
Original Poster
Kenko 2x converter modified for SDM!?!

A lot of things came in between, so called life, but now I've finally got around to finish up this little experiment.

I was planning to put together the converter without the circuit board, and replacing the board with something of the same thickness that passed the electrical contact straight through. But before spending to much time on finding that replacement, I decided to try the simple solution...to just mount it and hope that the missing distance would not make the contacts to loose.

Step 1: With the rear end of the converter open, replace all seven springs.


Step 2: Replace the little plastic piece that I'm calling "spring-guide" in lack of better words. It is in this step that we skip the chip.

It is easiest if you put the three screws in place first in the "spring-guide" before placing that one on top of the springs.


Step 3: Replace all seven springs on the seven rear contacts.

Place the seven contacts with the springs downwards into the "spring-guide".

Note the "gold" contact on the 2nd position.
This photo also show the start position that you must have before mounting the optics and rear-bayonet (which is one piece, see above). From the left you see a brass bar which is part of the bayonet lock, and must be in this position. Then comes the seven contacts fitted with the small plastic piece that guide the contacts into the whole in the bayonet mount. Then follows the SDM/power zoom contacts, and finally, the screw drive transfer axis (I'm making up a fair bit of home made English here, you have to live with it). That is tricky, especially in the other end inside the front end of the converter were the final piece in the screw drive can get loose inside the mount. When you get it back in position you have to place that screw drive transfer axis balancing on top of it, all the time without loosing your seven contacts with springs. Piece of cake

Step 4: I have no photos of this since all three hands were involved in holding the pieces. This is basically the work flow: Hold the front part of the converter with the front bayonet downward in one hand (not to loose contacts and screw drive pieces), then take the rear piece and fit it carefully into the first piece, first the optics (simple), then the old time aperture transfer (simple) and the arm that close the aperture mechanically (tricky) which basically has to be done at the same time as you fit the screw drive gears in the right position (to be able to do this you need to push the black plastic ring that are fitted around the bayonet to the side for a moment) fitting a small pin into the "screw drive transfer axis" (which will hold it in place) and if you have done this right, and not in the process lost the correct positioning of the seven contacts and the bar that connect to the bayonet lock, everything will finally fall into the right position and all seven contacts will show up in the seven holes in the bayonet. Piece of cake
The end result will look like:

And surprise, surprise, it looks like the two springs that act on each pair of contacts has enough pressure to keep the contacts well in position even without the circuit board. Here is the front end:


With great expectations I mounted the converter on the K20D and then the DA50-135...turn on the camera...it measures...but no autofocus of any sort and the camera flashing "MF". Perkele!

Wait a little bit...there is a chance yet...I noticed earlier when I took the converter apart in even more pieces that in the rear end, there is a black plastic ring around the mount and the optics on which the SDM/power zoom contact is mounted. Here it is removed (note that this picture was taken during an earlier part of the experiments where all seven contacts were removed):

A close up shows that removing the ring and the contact leaves a whole in which the two copper contacts I described four pictures up from here as the SDM/power zoom contacts on the inside of the converter.

As you can see on both pictures, the right one of the contacts are a bit missallinged. This could easily cause the contact to fail connecting to the rear piece of the converter and it is just impossible to control that in the complex three hand operation I've described above. But here and now, with this final piece of the SDM contacts at the rear bayonet removed, a little pressure with a small screw driver on the missallinged contact, and it behaves again. Putting the pieces back again...trying a second time...mounting converter and lens...turning on...:ugh:

...I HAVE SDM AUTOFOCUS!!!!!!!!!!!


OK, before deciding if it is a success, here is already passed midnight and I don't really have much motives to test shooting at. But it works. It is clearly not the screw drive that is activated, but the SDM engine. It hunts in a fairly dark room and it appears to over expose. But now I will sleep a bit and then test it out tomorrow.

PS. I skipped the details of one experiment. I tried mounting everything as described above, but without the G contact (the 7th contact that transfer lens info). The result was no autofocus at all. DS.

10-14-2008, 05:28 PM   #20
Site Supporter
hinman's Avatar

Join Date: Oct 2006
Location: Fremont, CA
Photos: Albums
Posts: 3,425
Big congratulation. You should think of investing in a Kenko 1.5x and get it to work for SDM lens and you can sell it for a profit. Thank you for all the documentation.
10-21-2008, 02:53 PM   #21
Site Supporter
Douglas_of_Sweden's Avatar

Join Date: Apr 2008
Location: Stockholm
Photos: Gallery
Posts: 3,347
Original Poster
Summary: Converting a Kenko 2x converter for SDM

Time to sum this up. Sorry that it took some time.

Having tested the modified converter for some days in different light conditions, the results are depressing. While SDM works, it hunts too much, often never reach focus in AF-S and in AF-C the pictures gets fussy because it shoot while still focusing.

First I thought it was also unable to get the exposure correct. Spent a good deal of thinking on trying to figure out why it would do that. I mean more than one or two full steps even!

Took me some days to realize that I got the aperture transfer arm a bit badly positioned so that the lens+converter was shooting wide open all the time! Took apart fixed and put together again. Then it exposed correct but still hunted like no focus hunting I ever seen. The modified converter works fine though with screwdrive autofocus lenses. As before the modification.

As I found the one page manual for the converter, I learned from it that the converter (the chip) does not modify the aperture information. So it does something for the power zoom I presume. What I don't know, and I have no power zoom camera to test on (though I might ask my brother if I can test it on his PZ1p some time). But in any case, the SDM is a failure, it does activate when the chip is removed and bypassed, but it does not function effectively.

From the many other tests I did we can guess/conclude some other things:
My hope was as a 2nd option when SDM failed to get the screwdrive focusing to activate (and for the light losses with a 2x converter I had my doubts already beforehand). Therefore I tried removing the SDM/power zoom contacts, in combos with and without the KA contacts and with and without the 7th data contact.

Somehow the K20D will not activate the screwdrive even without the chip because (me guessing what goes on in the K20D processor):
-with no A contacts at all it seas the lens/converter-combo as a K lens and does never activate the screwdrive (and not the SDM either in that modification combo)
-with the 6 old A contacts but without the 7th data contact, the camera seas the lens as a KA lens and does not activate any autofocus (because no such lens ever had autofocus)
-with all 7 A contacts and the screwdrive transfer in place but no SDM contacts it sees the lens as a F or FA lens...that was my biggest hope to activate the screwdrive...but the camera still does not activate the screwdrive...I assume it seas that it is a SDM lens (from some info sent by the 7th A contact) and activate the SMD (which does nothing since I disconnected it) not the screwdrive

So why does the SDM lens (DA*50-135) have a screwdrive connection at all?
To screwdrive focus on a camera without SDM!
Not to help me screwdrive focus through a modified converter!
Pentax put in preventions to avoid that, not trusting amateurs technicians like me or third party converter manufacturers that they would not happen to activate both SDM and screwdrive focus at the same time (which I carefully avoided), because it would probably seriously **** up the lens!!! Don't even want to think about what that could do to the poor lens!

With all in (except the chip)...well, call it an informative failure.
The power zoom contacts can skip the chip and connect as SDM contacts on the camera with the dito on the lens. But effectively it does not work...probably because of too large light losses in a 2x zoom.

QuoteOriginally posted by hinman Quote
Big congratulation. You should think of investing in a Kenko 1.5x and get it to work for SDM lens and you can sell it for a profit. Thank you for all the documentation.
Thanks hinman! But the congrats was a bit premature.
But along your line of thinking, I'm wondering if I could modify a Kenko 1.5x in this way? Now, here I'm confused...some Kenko 1.5x are reported to work with SDM and some don't!?!?
My Kenko 2x are labeled "Pz-AF 2x TELEPLUS MC 7". Me guessing the "Pz" is for powerzoom. How are the SDM capable Kenko 1.5x labeled? And the not capable?
Is there a pattern?

Not sure though I want to buy and modify a 1.5x with the Pentax converter around the corner, but if someone likes to donate a copy for the experiment...

A final note. The SMD/powerzoom connection in the rear end is so flimsy (is there such a word?) with two thin copper contacts not really attached to a weak peace of plastic that it could easily come out mounted in the wrong way even from a factory if no one test them, or if anyone ever have taken them apart. So if you have a 1.5x copy not doing SDM depressed because you have heard about others having a copy that does SDM, check the possibility that the piece of crappy plastics in the rear with the SMD contacts are not mounted correctly and fix it as I did some posts above.

Now back to the bigger project, the shoot out between the DA*50-135 and the best prime combo of the KA generation in that range: A50/1.7, A*85/1.4, A100/2.8 and the A*135/1.8...much more fun, have done portraits, walk about in the amusement park, some autumn landscape and a wall with bricks (dead boring) so far, but there is more to be done
10-21-2008, 04:18 PM   #22
Veteran Member




Join Date: Sep 2007
Location: West Virginia
Photos: Gallery
Posts: 338
Douglas, I am in awe of your perseverance and skills, not to mention exhausted from reading about your efforts. A noble attempt, however, and my compliments. I am one of those with an SDM - capable Kenko 1.5 and yes, it works but not nearly as well as the Tamron 1.4.......

Regards, JK
10-21-2008, 04:32 PM   #23
Site Supporter
Douglas_of_Sweden's Avatar

Join Date: Apr 2008
Location: Stockholm
Photos: Gallery
Posts: 3,347
Original Poster
QuoteOriginally posted by John Kovarik Quote
Douglas, I am in awe of your perseverance and skills, not to mention exhausted from reading about your efforts. A noble attempt, however, and my compliments. I am one of those with an SDM - capable Kenko 1.5 and yes, it works but not nearly as well as the Tamron 1.4.......

Regards, JK
Well, I always write too long, even when writing science papers
Basically its been driven by a frustration that a converter that appears to have all the right contacts for SDM did not work. Once I got the DA*50-135 I of course tried the my old converter within an hour or so. Expecting hunting, but puzzled that it did exactly nothing with neither focus methods.

What about your Kenko, is it also labeled as a "Pz-AF..."?
If there were initially both power zoom ("Pz") 1.5x and 2x Kenko converters, they must have decided only to upgrade the 1.5x version for SDM. Why? Or is it just an accident due to some small difference in the chips inside them (assuming now that the Kenko 1.5x does have a chip...please someone dare to take a look!)?

Ahh, a new idea! What if I take a chip from an (upgraded?) Kenko 1.5x that does SDM and put it into a Kenko 2x?!? I think I might have to get one of those 1.5ers, perhaps they will drop in price when the Pentax converter will come. Even though with a Pentax 1.4x converter, the option of a 2x SDM converter is tempting even if it works less good.

10-22-2008, 04:52 AM   #24
Veteran Member




Join Date: Sep 2007
Location: West Virginia
Photos: Gallery
Posts: 338
Kenko Pz

Yes, Douglas - Pz, as the pic below shows. Though IQ is fine the TC seems to 'hunt' for focus noticeably much more than the Tamron, though this is subjective from my experience only. I do think others have said the same. Interestingly, the Promaster 1.7 will actuate SDM but not complete the focus for some reason.
Attached Images
View Picture EXIF
PENTAX K100D  Photo 
10-22-2008, 05:21 AM   #25
Site Supporter
Douglas_of_Sweden's Avatar

Join Date: Apr 2008
Location: Stockholm
Photos: Gallery
Posts: 3,347
Original Poster
QuoteOriginally posted by John Kovarik Quote
Yes, Douglas - Pz, as the pic below shows. Though IQ is fine the TC seems to 'hunt' for focus noticeably much more than the Tamron, though this is subjective from my experience only. I do think others have said the same. Interestingly, the Promaster 1.7 will actuate SDM but not complete the focus for some reason.
It appears that the "Pz" is there even on the Tamron 1.4x (see the long thread that was on this forum earlier this year). So does it really mean Powerzoom?

A difference between the 1.5x Kenko is the "SHQ", which is not on either the Kenko 2x or the Tamron 1.4x. Any idea what it stands for? Super High Quality? Anything to do with SDM?

I know it has been speculated that the 1.4x gets away with it just because it is that tiny little bit brighter than the 1.5x. Just hard to believe that it could be that sensible for such a small difference. But it could be why Pentax is going for 1.4x in their converter. SDM can't just handle any larger converters?!

What we know now is that while the chip is the real reason why 2x is stone dead, the converted converter with no chip "actuate SDM but not complete the focus for some reason" just like the promaster you mention. The promaster being 1.7x and the Kenko 2x it could be due to too large light losses for both.

Then again, looking at how thin the 1.5x and the 1.4x is, is there really any chip in those? And if there is, what would happen if I take it out (the Kenko 1.5x chip SHQ) and put it in the Kenko 2x?

I also appear to recall some people claiming their Kenko 1.5x does not autofocus. Why? Two versions (one upgraded SHQ, one with an old chip)? Speculating freely...

But probably it is (chip excluded) all about light losses...so final option would be to remove chip and optics from the 2x Kenko and get a SDM and screwdrive capable extension tube! Whatever I would want that for...
10-22-2008, 05:32 AM   #26
Veteran Member
eurostar's Avatar

Join Date: Dec 2006
Location: Albareto, Italy
Photos: Gallery
Posts: 813
QuoteOriginally posted by Douglas_of_Sweden Quote
A difference between the 1.5x Kenko is the "SHQ", which is not on either the Kenko 2x or the Tamron 1.4x. Any idea what it stands for? Super High Quality? Anything to do with SDM?
I bought my SHQ Kenko 1,5 at least ten years ago, and by the SDM were not invented yet. It indeed stands for super high quality.
10-22-2008, 09:31 AM   #27
Veteran Member




Join Date: Sep 2007
Location: West Virginia
Photos: Gallery
Posts: 338
The 'brighness' conjecture may explain it as it would cover both the Kenko 1.5 and the Promaster 1.7 behaviors, but what do I know? Ha! Assuming that to be the case, then the answer could only be found inside the camera body. Go for it!
10-22-2008, 05:52 PM   #28
Site Supporter
Douglas_of_Sweden's Avatar

Join Date: Apr 2008
Location: Stockholm
Photos: Gallery
Posts: 3,347
Original Poster
QuoteOriginally posted by John Kovarik Quote
The 'brighness' conjecture may explain it as it would cover both the Kenko 1.5 and the Promaster 1.7 behaviors, but what do I know? Ha! Assuming that to be the case, then the answer could only be found inside the camera body. Go for it!
No, not the K20D. Would be slightly depressed if I couldn't put it together again. But have been considering removing the IR filter on the *istDS sensor myself, there is a good description on the web. If that works well, who know what will happens to my confidence Well, seriously speaking, I don't want to disturb the little guy in there who runs the camera...

I've found the Kenko 1.5 SHQ on the ebay, but since it is not working really well either (compared to the Tamron), I don't think it is worth it to buy it just to try to move the chip to the Kenko 2x, when 1) there isn't sure there even is a chip in the 1.5x 2) it is probably limited by the light loss anyway. Pentax 1.4x is around the corner anyway.
But the more I think of it I think I will try to remove the optics and the chip (chip is currently back in again) in the Kenko 2x to make the first and only SDM extension tube
10-22-2008, 06:06 PM   #29
Site Supporter
Douglas_of_Sweden's Avatar

Join Date: Apr 2008
Location: Stockholm
Photos: Gallery
Posts: 3,347
Original Poster
QuoteOriginally posted by eurostar Quote
I bought my SHQ Kenko 1,5 at least ten years ago, and by the SDM were not invented yet. It indeed stands for super high quality.
Thank you, good to have that confirmed.
A bit odd to call the MC4 optics for "super high quality" and not the better MC7 optics.
Would have been nice to have someone with a powerzoom camera and powerzoom lens and any of the "Pz" converters to comment how they work with these.

Also, considering my guesses above why the camera cannot be fooled to activate the screw drive focus, it is a pity that Pentax appears to have closed that door completely. I mean, the Kenko 2x works fine with screwdrive lenses, even my FA28-80/4 which is a full stop darker than the DA*50-135, so certainly it could have worked as a screwdrive converter even on the SDM lenses if Pentax had left an open door somewhere, like an option to dissable SDM in favor of screwdrive in the menue. Optically the Kenko 2x and the DA*50-135 is one of the better combos I've seen, at least for a zoom. But I think I have exhausted all options to get around the SDM and activate the screwdrive.
10-23-2008, 12:22 PM   #30
Pentaxian
Lowell Goudge's Avatar

Join Date: Jan 2007
Location: Toronto
Photos: Gallery | Albums
Posts: 15,312
slight change in modification?

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.
Reply

Bookmarks
  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
2x, autofocus, contacts, converter, exposure, k-mount, kenko, lenses, pentax lens, power, screwdrive, sdm, slr lens
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Pentax 50-135mm SDM DA* F2.8 w/ kenko x2 converter bezuidar Pentax SLR Lens Discussion 2 09-02-2010 09:47 PM
Kenko converter 1.5 BCtoad Pentax SLR Lens Discussion 4 08-29-2010 08:40 AM
Wanted - Acquired: Kenko 1.5X or Tamron 1.4X AF converter 7.62lew Sold Items 2 12-01-2009 02:48 PM
Kenko Teleconverters and SDM channeler Pentax SLR Lens Discussion 4 04-24-2008 04:03 PM
KENKO 1.5X DG af Teleplus Tele-converter jpdsr3 Pentax DSLR Discussion 6 04-16-2008 07:18 PM



All times are GMT -7. The time now is 12:10 PM. | See also: NikonForums.com, part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top