Tamron Adaptall-2 P/KA Adapter

Tamron Adaptall2 P/KA adapter

Tamron Adaptall2 P/KA adapter
I have two copies of this P/KA adapter that works with Adaptall-2 lens. This PK/A can work with Auto aperture with Tamron adaptall-2 lens. My most recent copy is a brand new one. They are more expensive than the P/K adapter as they allow the Av mode saving the extra step in stop-down meterring. Though more expensive and harder to find a good copy to purchase, I will recommend this adapter over others.

There is one common caveat that happen to these PK/A adapters, I have problems with loose connection with both copies where the actual apertures in Av mode is not displayed and the maximum aperture that I can select in e-dial only goes to f/4.0 and not anything bigger. My first copy of the PK/A adapter refuses to go to f/3.5 for my 19AH zoom and I can't select f/2.5 for my 52BB macro. After many trials of cleaning the contacts, I gave up on my 1st adapter and sold it to others with full disclosure on the problems.

Many have reported to similar problems. Some reported success to perform minor scraping of screw heads with either a sharp knife or sand paper on the adapter. I have taken many trials and my problems is not totally gone as my problems of disappearing F/aperture still happens intermiddently with my 2nd copy of the adapter. The scraping may improve the connection between the electrical contacts with those in the K mount. With my 2nd copy, I manage to select f/3.5 for the 19AH zoom.

Many thought that there is a thin film of coating on the adapter that prevents the accurate connection with the electrical contacts. Others suggest a inaccurate mounting design that give rise to the loose connection. I still find occasional need to wiggle the lens mount to see the LCD display of the f/aperture in Av mode.

It is very unsettled to get an adapter that only goes to f/4.0 and I am yet to use the trick of adding a small piece of aluminum foil in between the adapter and the K mount and see if it improves the connection further.

  • I found remounting the adapter sometime do help with loose connection
  • In the case of aperture displayed as "F--" on the top LCD display, a quick wiggle in clockwise direction seems what it takes to fix the problem
  • For aperture that goes only to f/4.0, I found using a sand-paper or something that is safe to scrape off the thin films covering the electrical contacts on the adaptall-2 mount the most effective.
  • For lens at f/3.8 maximum aperture, the display in Av aperture can only go to f/4.0 and I think that is not fixable unless you change to M mode and use stop-down metering.
  • Contrary to what I say before that adding a thin aluminum foil as in M42 mount to get focus trap enabled, I was not able to improve the electrical connection with the adaptall-2 adapter in using foil.
  • A great tip that I have learned and found extremely useful in easing the dismounting: remember to set aperture to smallest using the black tab before engaging the silver tab for dismount.



Laur said...

Interesting. I wasn't aware of these issues and these adapters are pretty expensive for Pentax.

I got around all this by getting a basic PK adapter that can be had for much cheaper. It allows me to use the lens in Av mode because it practically becomes a preset. Something worth considering as an alternative.

Hin Man said...

@Laur, this is new to me as I have used PK adapter but it can't serve me in Av mode as I tend to think that in Av mode, it is metering wide open for me. I can be wrong but please do check if in Av mode, your shutter changes with aperture stops.

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