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09-16-2013, 12:31 PM   #1
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Tamron 23A Adaptall-2 and Apertures

I just got a Tamron 23A 60-300mm adaptall-2 zoom lens, and note that the aperture seems to require manual stopping down for metering, it doesn't stay open when on the camera. Pushing the lever on the unmounted lens operates the aperture so something is awry, anyone know how to tell whether it is the adaptall 2 mount or the lens, or is this expected with the 23A?

Camera is a KM (film KM, not digital K-M). This functionality works fine on all my other lenses.

To be clear, I am not talking about Auto-Aperture as in the camera body chooses the aperture for auto-exposure, I mean auto-stopping-down when the shutter is released.

(Purchased from Keh, so I am trying to determine if this is a return.)

09-16-2013, 01:51 PM   #2
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Just to be sure, before I say more: Your lens is with the ordinary P/K custom mount? (and thus: neither with M42 screw mount or P/KA mount with electrical contacts).

IF you got the "ordinary" P/K mount it should certainly work as any manual K-mount lens with any Adaptall-2 lens. First thing I would check is if the custom mount is placed correctly on the lens. There are two "ears" that can rotate relatively to each other and that must fit into two fixed slots on the lens.
09-16-2013, 02:10 PM   #3
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QuoteOriginally posted by Stone G. Quote
Just to be sure, before I say more: Your lens is with the ordinary P/K custom mount? (and thus: neither with M42 screw mount or P/KA mount with electrical contacts).

IF you got the "ordinary" P/K mount it should certainly work as any manual K-mount lens with any Adaptall-2 lens. First thing I would check is if the custom mount is placed correctly on the lens. There are two "ears" that can rotate relatively to each other and that must fit into two fixed slots on the lens.
It is the ordinary P/K mount and I have seated and re-seated the mount multiple times as well as seated and re-seated the lens multiple times. I think either the lens or the mount is bad but can't determine because I don't have alternates to compare. After talking to KEH on the phone I'll just send it back, the lens has a couple other problems (won't go into Macro, focuses past infinity) so in general I am just going to start over.
09-16-2013, 02:49 PM   #4
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Sounds like you've made the right decision with that copy!

09-16-2013, 03:04 PM   #5
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QuoteOriginally posted by Stone G. Quote
Sounds like you've made the right decision with that copy!
yeah, especially since I was replacing my Sears 60-300 because it focuses past infinity.
09-16-2013, 07:53 PM   #6
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Test the auto-aperture feature with the adapter off the lens. The actuator mechanism is pretty obvious. Depress it to test the aperture function. If that is working properly, the problem is with the adapter. The adapter can also be tested when off the lens. In the resting position the actuator plate should be essentially flush with rear light baffle and should drop when the (spring-loaded) lever is tripped. The mechanism is exposed to view and any damage or malfunction should be pretty obvious.


Steve
09-16-2013, 09:00 PM   #7
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Yeah, both work fine individually and when coupled when not mounted to the camera. I suspect the aperture lever is slightly bent or something similar, but I have nothing to compare. I sent it back already, life's too short to worry about it. I just wanted to be sure it wasn't me misunderstanding something, first.
09-16-2013, 09:43 PM   #8
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A couple of questions here

First, with the lens off camera, and stopped down, does activation of the lever open the aperture. Second, if you remove the mount from the lens, does the mechanism work.. You may just have a bad mount.

Or perhaps and this is a guess, you have an aftermarket mount not a true adaptall mount, in which case it will only manually stop down.

09-17-2013, 11:39 AM   #9
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QuoteOriginally posted by Archimedes the Dog Quote
I suspect the aperture lever is slightly bent or something similar, but I have nothing to compare.
Yep...that might cause a problem. The PK adapter's lever has no protective shroud and as a result is easily bent.


Steve
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