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08-28-2011, 09:13 AM   #1
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Adaptall-2 Adapter Question

I hope this is the right place for the question,

I know most of you are familiar with the both Tamron Adaptall-2 adapters with diaphragm control pin with and without electrical contacts, but I never saw this one before, it seems it has no diaphragm control pin so you have to set your aperture manually after you focus unless you are are shooting wide open. Is my assumption correct?

Tamron AD2 Adaptall 2 Adapter to Pentax K10D K20D Km K7 | eBay

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08-28-2011, 09:22 AM   #2
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Great to see this thread is working the other is now gone.
08-28-2011, 09:50 AM   #3
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QuoteOriginally posted by cbaytan Quote
I hope this is the right place for the question,

I know most of you are familiar with the both Tamron Adaptall-2 adapters with diaphragm control pin with and without electrical contacts, but I never saw this one before, it seems it has no diaphragm control pin so you have to set your aperture manually after you focus unless you are are shooting wide open. Is my assumption correct?

Tamron AD2 Adaptall 2 Adapter to Pentax K10D K20D Km K7 | eBay
That's the Chinese made PK Adaptall adapter; no moving parts. Ideal for Tamon mirror lenses or if you like shooting in Av mode (stop down metering).

Thanks,
08-28-2011, 10:03 AM   #4
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Yes. It's not too hard to find the Tamron made adapter that makes the lens work like a manual K mount (with no "A" setting). I have one of those for each of my Adaptall lenses. I never felt it was worth it to me for the premium you pay for the "A" type adapter, but I would rather not have to use the lens like an M42 if I don't have to.

08-29-2011, 01:08 PM   #5
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QuoteOriginally posted by CFWhitman Quote
would rather not have to use the lens like an M42 if I don't have to.
+1 on this comment. M mode with green button and aperture coupling for stop-down (historically called auto-aperture) is much nicer than shooting with a full manual aperture. Even a pre-set aperture is preferable.

Steve

(...regularly shoots with a variety of vintage lenses...)
08-29-2011, 02:28 PM   #6
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QuoteOriginally posted by excanonfd Quote
That's the Chinese made PK Adaptall adapter; no moving parts. Ideal for Tamon mirror lenses or if you like shooting in Av mode (stop down metering).

Thanks,
You can use the Tamron mirror lens in Av mode because it has no aperture. Other lenses (M&K) will not work in Av mode because it will not control the aperture ring. They too, regardless of the aperture ring, will shoot wide open. To use Stop Down metering, with an M or K lens (non - A or non m42 types), you must use M mode.

08-29-2011, 08:21 PM   #7
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QuoteOriginally posted by JeffJS Quote
You can use the Tamron mirror lens in Av mode because it has no aperture. Other lenses (M&K) will not work in Av mode because it will not control the aperture ring. They too, regardless of the aperture ring, will shoot wide open. To use Stop Down metering, with an M or K lens (non - A or non m42 types), you must use M mode.

There seem to be a difference of opinion as to what stop down metering is. You seem to consider shooting in M mode with the shooter dialing in the aperture setting on the lens' aperture ring, press the green button to meter as stop down metering, you may be setting the desired aperture value, but it is the shutter actuating that stops the lens down to the said value and the viewfinder's brightness remain unchanged, an automatic feature. What I consider stop down metering is that when I set the desired aperture value on the lens, there is an immediate reaction to doing so; viewfinder brightness change, shutter speed changes in inverse relation to the aperture value, which is what shooting with an m42 lens with a PK adapter does. If you take any Adaptall(-2) lens and mount it to this third party PK Adaptall mount, the lens will behave exactly the same as an m42 lens mounted on your DSLR with an m42 to PK adapter (which fits in with my definition of stop down metering).

Thanks,
08-29-2011, 08:35 PM   #8
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QuoteOriginally posted by stevebrot Quote
+1 on this comment. M mode with green button and aperture coupling for stop-down (historically called auto-aperture) is much nicer than shooting with a full manual aperture. Even a pre-set aperture is preferable.

Steve

(...regularly shoots with a variety of vintage lenses...)
I don't understand where you would differentiate between a preset lens and an m42 lens. I know you prefer shooting Tamron Adaptall-2 lenses with a PK/M mount, whereas I prefer the PK/A mount. Aha, I have a deal for you Steve, send me your PK/A mount and I'll send you two PK/M mounts.

Thanks,

08-30-2011, 07:21 AM   #9
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Trying to compare Adaptall lens functions with the various exposure modes associated with the Pentax mounts gets confusing in a hurry -- and I suspect it causes some of the 'bumfuzzled' discussions seen here. Much as the differences in M42 lenses with or without the A/M switch and aperture activation pin still does.

It's useful to limit the description of the capabilities to the lens only where PK or PK/A functions are definitive and aren't dependent on the camera body, exposure modes or personal preferences/techniques.

It's also useful to remember that the PK/A adapter was designed before the present generation of "smart" bodies arrived and had to be "universal" enough to be commercially viable with many brands to survive. The trend toward unique screw-drive, auto focus designs pretty much killed the potential for a viable universal adapter from the economical manufacturing point of view. Tamron still does quite well with mount-specific lenses where the market share allows.

It would have been interesting to see the possibilities for Adaptall evolution if the interaction between bodies and lenses had skipped the intermediate electro-mechanical design phase and gone directly to a purely digital-electronic "fly-by-wire" design with SDM type motors. I believe that would have made it practicable to compete with OEM-AF lenses in this auto focus era using the Adaptall mount concept -- and that feature still might renew interest in the concept.

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