[timw4mail]

So a little while back I bought a Pentax ES mount adapter (For the SP F, Electro-spotmatic, ES, ES II).

The thing is, that it is very finicky in actually allowing open-aperture metering.

Do you have any suggestions on how to make it work more reliably? The lens that seems to work the best with it is also the lens that has the tightest fit.

[stevebrot]

So a little while back I bought a Pentax ES mount adapter (For the SP F, Electro-spotmatic, ES, ES II).

The thing is, that it is very finicky in actually allowing open-aperture metering.

Do you have any suggestions on how to make it work more reliably? The lens that seems to work the best with it is also the lens that has the tightest fit.

Might you elaborate on how it is failing and on what camera? Edit: The indexing for aperture ring position is done via the tab on the adapter. Other than that the attached lens should make no difference. What happens if the adapter alone is attached to the camera; does the meter respond when the tab is slid from side to side? Note that the tab must be engaged for the feature to work properly.


Steve

[timw4mail]

Might you elaborate on how it is failing and on what camera?


Steve

On both my SP F, and Electro-spotmatic, open aperture metering is non functional, only stop-down metering works. That's the most common case. Sometimes, if I get the adapter on just the right lens, just right, then it (open aperture metering) works.

[stevebrot]

On both my SP F, and Electro-spotmatic, open aperture metering is non functional, only stop-down metering works. That's the most common case. Sometimes, if I get the adapter on just the right lens, just right, then it (open aperture metering) works.

I added a bit more text while you were responding, see above...


Steve

[timw4mail]

The mount does seem to work on the camera.

[redbirdpete]

I had one (genuine) Tamron ES adapter where the lug that fits in the slot on the lens had been weakened over time and wouldn't turn with the aperture ring. It seemed to work fine with no lens attached. Some have a solid lug, the kind with the problem had a pressed lug.

[timw4mail]

I had one (genuine) Tamron ES adapter where the lug that fits in the slot on the lens had been weakened over time and wouldn't turn with the aperture ring. It seemed to work fine with no lens attached. Some have a solid lug, the kind with the problem had a pressed lug.

Yeah, the one I have has a pressed lug.

It seems like I have better luck if I mount the lens at minimum aperture (like f22), but that also seems to affect the accuracy of metering for the maximum aperture.

So, is there a copy of the Tamron adapter that works with open-aperture metering, or is open-aperture metering just finicky with Adaptall lenses?

[stevebrot]

So, is there a copy of the Tamron adapter that works with open-aperture metering, or is open-aperture metering just finicky with Adaptall lenses?

Your adapter is designed to support open-aperture metering, but will only do so properly if in good working condition, including the coupling tabs (lug) with the tabs engaged to the lens. I have several Adaptall-2 lenses and a collection of adapters for different mounts (mostly Adaptall-2, but one Adaptall) and all engage easily with no tendency to pop out. None seat themselves auto-magically, though often enough they will do so if the lens is attached according to Tamron instructions.* If the tab is not seated, it is easy enough to slide it into place BEFORE mounting to the camera.


Steve

* The instructions are increasingly hard to come by, but in simplest terms, the aperture ring on the lens should be set to the widest aperture for both attaching and detaching the adapter. This is particularly important for adapters such as the PKA where mechanical interlocks may be wrong with improper attachment/detachment.

[timw4mail]

Your adapter is designed to support open-aperture metering, but will only do so properly if in good working condition, including the coupling tabs (lug) with the tabs engaged to the lens. I have several Adaptall-2 lenses and a collection of adapters for different mounts (mostly Adaptall-2, but one Adaptall) and all engage easily with no tendency to pop out. None seat themselves auto-magically, though often enough they will do so if the lens is attached according to Tamron instructions.* If the tab is not seated, it is easy enough to slide it into place BEFORE mounting to the camera.


Steve

* The instructions are increasingly hard to come by, but in simplest terms, the aperture ring on the lens should be set to the widest aperture for both attaching and detaching the adapter. This is particularly important for adapters such as the PKA where mechanical interlocks may be wrong with improper attachment/detachment.

I do know that the widest aperture should be used for attaching the mount. I meant that screwing the attached mount to the camera, I had better luck with the lens at the smallest aperture.