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Old Apr 21, 2008, 7:06 PM   #1
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I have an old Cosina 200mm F3.8 K-mount lens(25 years old), which works fine with K10D (manual focus of course, & no electrical pins for aperture info!!).But when I use anew Kenko Teleconverter (it has the Tv & P mode electrical contacts on it)with it, it shows no aperture on the camera, and I can't take the shot.

I've tried it with a newer manual focus Tokina(20 years old KA mount, with the electrical contacts), and it works in Auto aperture mode on the lens, but when I switch the lensto manual apertures, the Teleconverter again fails to allow me to take the shot. (e.g. in that situation, the Tokina is effectively in the same mode as the Cosina.)

So the question is, why does the Cosina work quite happily on the K10D, but not on the K10D with the teleconverter attached??

With the Cosina having no electrical "pins", would I have to blank offthe "missing" electrical "pins" on the Cosina to trick the teleconverter into thinking it is getting some info from the Cosina?

(I understand the "1" and "0" patterns for the pins on the KA, and how they give aperture and minimum aperture information to the camera)

So to summarise:

Cosina K-mount works with K10D

Tokina KA-mount works with K10D

Tokina KA-mount, with Tele, "A-aperture" modeworks with K10D

Tokina KA-mount, with Tele, F number aperture(non A-aperture)modedoes NOT work with K10D

Cosina K-mount , with Tele, F number aperture does NOT work with K10D
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Old Apr 21, 2008, 8:22 PM   #2
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I've yet to find a lens TC combo that won't work with the K10D. All manual including the AF in manual and it works great! I quite often use a Vivitar 300mm f/5.6 lens (All Manual) coupled with a Sigma AF TC. Not had a single problemn with it! But like I said in full manual mode including the AF. With the AF in Auto mode it will work (of course there is no Auto focus going on) but it won't allow some shots if I put it in Aperture priority this way. In other words the camera Exposure is not right so the shutter refuses to work...But if I move the auto focus lever to manual it will allow it! I think I said that right!! LOL

Dawg
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Old Apr 22, 2008, 12:00 AM   #3
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Hi dnas,

I'm not sure if I understand the problem, but do you have the Custom Menu item "Using Aperture Ring" set to "Permitted"? If not, this might be the cause. I can't test it because I don't have any lenses without the contacts.

Scott
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Old Apr 22, 2008, 12:18 AM   #4
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Well, to put it concisely:

When I attach the Cosina K-Mount (manual focus, no contacts) 200mm lens to the K10D, it works fine.

When I then attach the Kenko (new, with contacts on it) teleconverter between the Cosina lens and the camera, then the camera shows "no F stop", so I CAN'T get the shutter to fire.


I can't look at the Custom Menu until I get home from work....
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Old Apr 22, 2008, 3:49 AM   #5
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Ok, well I've set the Custom Menu item "Using Aperture Ring" to "Permitted", and it works!!!!!

Thank you very much!!!!!

However, why then, does it work when I put the Cosina lens on with "Using Aperture Ring" to "Prohibitted"??? It doesn't seem to make any sense!!!!
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Old Apr 22, 2008, 3:50 AM   #6
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i am intresting in your service


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Old Apr 22, 2008, 7:02 AM   #7
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I've tried a few other lenses, and it seems to make a difference as to whether the K-mount is black or not!!(if in the "Using Aperture Ring" to "Prohibitted" mode) e.g. the Cosina is black and NOT conductive to to electricity, while a 50mm F1.4 is bare metal and conductive, and doesn't work!!!!
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Old Apr 22, 2008, 12:06 PM   #8
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dnas wrote:
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I've tried a few other lenses, and it seems to make a difference as to whether the K-mount is black or not!!(if in the "Using Aperture Ring" to "Prohibitted" mode)* e.g. the Cosina is black and NOT conductive to to electricity, while a 50mm F1.4 is bare metal and conductive, and doesn't work!!!!
Hi dnas,

I've never had enough curiosity to really look into this, but my guess is that the conductivity at the pin sites is the difference. I think that the system needs a ground at at least one of the pin sites to work as designed. The black color is probably paint, and it insulates the grounding pin(s)from the rest of the system. I'm guessing that if you remove the paint from the rear surface of the lens, everything'll work as designed.

That's what I'd do -- make all the lenses work the same, and leave the "Use Aperture Ring" on "Permitted" permanently. One less thing to worry about when setting up to shoot.

Scott
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Old Apr 22, 2008, 5:51 PM   #9
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i've noticed this with my A2x-s using lenses without the contacts. with a manual lens attached in manual modew/the TC attached the cam does not close the lens down. get some sheet, very thin plastic and when you mount the lens short the contacts with the plastic..what i do is carry a clear baggie in my kit for this..
you will NEVER get an aperture reading on the cam using a fully manual lens..

roy
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Old Apr 22, 2008, 5:58 PM   #10
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I also have an older *ist DL2, and the non black K-mount lenses do not work on that, but the black Cosina DOES!!! I've set the K10D to "permitted", so everything seems to work as expected.

However, if I remove paint from the Cosina lens, it will stop working with the *ist DL2!!! I thought that it would interest other people to know how the conductivity of the lens mount on the lens influences the way K-mount lenses work with different cameras.

e.g. If you have an older K-mountlens that doesn't work with the *ist DS, DL, DL2, etc,then PAINTING the area where the pins normally are, couldmake them work!! (I'd be careful about the type of paint though. You wouldn't want it coming off, and onto/into the camera body!!!)





snostorm wrote:
Quote:
dnas wrote:
Quote:
I've tried a few other lenses, and it seems to make a difference as to whether the K-mount is black or not!!(if in the "Using Aperture Ring" to "Prohibitted" mode) e.g. the Cosina is black and NOT conductive to to electricity, while a 50mm F1.4 is bare metal and conductive, and doesn't work!!!!
Hi dnas,

I've never had enough curiosity to really look into this, but my guess is that the conductivity at the pin sites is the difference. I think that the system needs a ground at at least one of the pin sites to work as designed. The black color is probably paint, and it insulates the grounding pin(s)from the rest of the system. I'm guessing that if you remove the paint from the rear surface of the lens, everything'll work as designed.

That's what I'd do -- make all the lenses work the same, and leave the "Use Aperture Ring" on "Permitted" permanently. One less thing to worry about when setting up to shoot.

Scott
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