Originally posted by Lowell Goudge What you have described is physically impossible. The A contact is supposed to be recessed on the body, a simply conducting base does nothing, because it cannot project into the space where the pin is recessed. If your k10 does this then it will also do it with K mounts. Check and see if someone has installed a wrong pin
Lowell,
Perhaps I can send you a photo of the top LCD showing aperture setting when the J-9 is mounted? As for somebody installing the wrong pin...it would have to have been a factory job. I bought my K10D new in '07. As for the pin being recessed...you are correct. The A pin is only supposed to have continuity when an A lens is mounted and aperture ring is in the A position. On some lenses the pin retracts. On others there is an internal switch that breaks the circuit.
So...how/why does this happen? Hard to say, but these are the facts with my setup:
- I own dozens of lenses, both M42 and K-mount and the J-9 is the only lens that has this behavior
- Even so, it is VERY sporadic and unpredictable and has caused lost shots before I noticed that things did not look right in the viewfinder
- At one point I put a multimeter across the lens base from one side to the other and the unbroken finish passes current, though with some resistance. None of my other M42 lenses do this.
As a result, I am unwilling to state that there is no camera logic gated by conductivity outside the A contact with the K10D.
Back to the discussion...
Shorting the contacts does not improve meter performance on the K10D or K20D when used with non-A contact lenses. Been there, tried that several years ago when the rumors first started. The Kx00D series may be another matter however.
I have not tested the K-5, K-r, or K-x, but I have tested the K-7 and conductive base does not change meter performance in Av mode. M mode works equally well (meaning very good) with both conductive and non-conductive bases. The K-5 is supposed to have the same meter logic as the K-7.
As for Av mode...All, except (by all reports) the *istD, may suffer from poor metering in Av mode. It depends on lens and aperture when metering.
Rico is correct...M42 and non-A contact K-mount should behave identically (except for my Jupiter-9 and it is possessed) on K10D and K20D and the K-hyphen models. Again the Kx00D models may be different.
Regarding street photography using Av mode and the ST 28/3.5...It does not surprise me that Av works great for you with minimal need for compensation. My personal research has indicated that most of the metering issues occur at f/3.5-f/4 and wider. I regularly shoot my Tamron 70-150 with the standard PK mount using green button only and no compensation. Works great.
One more thing before I go to bed...Pentax is not the only brand with meter issues using vintage lenses. Poor stop-down meter performance is a problem across brands. You just don't read the complaints from Canon and Nikon owners here.
Steve