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07-11-2012, 03:42 AM   #1
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help with PKA adaptor

Hi,

I am having trouble with pka adaptor when using it with TC 01F 2x and 90mm F2.8 macro (72B).

Using the adaptor on the 72B directly work better. AE and non-AE all works.

Aperture range is recored correctly at F2.8 - F22 (I assume this is correct, since F32 is for AE).

Only problem is that, some time I get F-.-, and need to jiggle the lens a bit to get it to work.

When it works, all is fine. A bit annoyed by the F-.- (when i get this without knowing it, the exposure will be all wrong).


When I use it with the TC, the same problem with F-.- is still there. Seems to happen more often, but it might be just my impression.

But the aperture range is wrong. Its sometimes show F4.0 - F22, and other times show F2.8 - F22. Its very unstable.

It should be F5.6 - F45 isn't it?

Exposure is ok, but I feel it is over expose by one stop, when it show the range of F4-F22. Have to test it more, especially when it show F2.8-F22 (to check if I get 2 stop over exposure). It is not conclusive at the moment.

I hope to fix this if possible.

A second problem, not so important, because I seldom use non-AE mode, but it could indicate what is wrong with my adaptor.

With TC, If move away from AE, then the lens will only work wide open regardless of my aperture ring position (when I use non-AE, I always do M mode and set my own exposure). So using "correct" shutter speed, will result in over exposure because the lens will not stop down.

One observation that might mean something: I need to press the black tab on the adaptor lightly to set the aperture ring to AE mode. Otherwise, it will stuck at F22. This is true when use with and without the TC. Not sure if this is normal.

I try to mount the TC and the adaptor using the steps I found in this forum. Follow it exactly. Still no joy.

I have also try to clean the contact (the 3 small screw) as suggested by an old thread here. Again, no change.

All these items are from seller in the marketplace in this forum, and they should be in good shape. Maybe I did something wrong.

Any help and suggestion will be very much appreciated. Thanks in advance.

-kk

07-11-2012, 11:40 AM   #2
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HI kkx,

I cannot answer all of your questions, but perhaps some of them:

We are talking Tamron Adaptall-2 lenses and PK/A custom mounts for these lenses.

Aperture Range: It will (should) show 2.8 - 22 irrespecftive of whether you use TC or not in AE-mode. The TC only reports the seeting of the lens; it is not "intelligent" and will not compute the actual f-ratio. But you will get (should get) proper exposure anyway.

F--- and need to jiggle: Yes, we all know about that. It is a fact that these adapters are delicate items and some are more worn than others. But

The fact that you report that your lens will not stop down when the lens is in non-AE mode indicates something more problematic. In non-AE mode, you can only operate with the camera body in M-mode, but then the lens should certainly also stop down when you release the shutter. Are you sure you have set your program dial at that M-mode?

Also, the question about the "black tap" indicates to me that you are not completely familiar with the procedures for using and installing the mount. You MUST depress the "black tap" to shift from AE to manual. If you use force here, you may damage both adapter and lens. I suggest that you download the instruction manuals (pdf-files) for both adapter and TC from my homepage here:

PhotoDocs

You will find the adapter manual in the second and the TC manual in the third block of documents. Please also note the instructions for mounting and dismounting the adapter - IN PARTICULAR that the aperture must be set at its widest!!!

Overexposure: I don't know your 72B, but I have 8 other adaptall-2 lenses and yes, some of them tend to over expose. It is quite easy to correct for that using the EV compensation. My lenses usually like a compensation of either 0 or some -0.7 to -1 EV.

Finally, if you haven't found your way already, I suggest that you vist the Adaptall Lens Club page in this Forum, where you will find a lot of valuable information and inspiration to the facinating world of Tamrom Adaptall lenses.

https://www.pentaxforums.com/forums/lens-clubs/59769-adaptall-mount-club-tamron.html

I hope, this helps a little bit.

Last edited by Stone G.; 07-11-2012 at 11:45 AM.
07-11-2012, 11:02 PM   #3
kkx
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Thanks for the helpful and detailed reply.

The pdf manual is very useful.

I follow the instruction carefully and redo everything.

I didn't know that I need to press the black tap before I can set the lens to AE mode. Thanks for telling me. Luckily I didn't force anything, so nothing broken.

If the range of 2.8-22 is correct when I use the TC, then all is ok. Sometimes I get 4.0-22, I think that is due to poor contact.

About AE not working, I have finally found out why.

I have a mod on my K-5 body. Shorted the A pin with some tin foil. Totally forgotten about that. So my body will not operate on K-M mode correctly. My bad.

Tested the whole system properly and all seems fine.

Thanks, and I will visit the Adaptall club, lots of nice info there. Will be useful to guide me to my next adaptall lens.

Thanks again.

-kk
07-12-2012, 04:02 AM   #4
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Note that the occasional F4 is the result of lock of contact between the mount base and the sliding connection arrangement that changes the pin contacts for different lenses. It comes from time to time, mostly due to dirt and non use. Same as the F-- issue.

One additional thing, while the lens and camera may meter correctly, (consistently) the may be a constant exposure error when using the TC because the camera thinks it is F2.8 not 5.6 and will make an adjustment, this will require a constant. EV comp adjustment. When using flash. You will need to set EV comp on Bo the camera and flash because the flash calculations get errors introduced wen trying to balance the ratio of fill flash to natural light.

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