[atarget]

Recently I purchased SMC Tak 135/1:3.5 and SMC Tak 28/1:3.5 and tried to test them on K5. I put on Pentax proprietary M42-PK adaptor as I usually do. Auto-man switches for both lenses were set to "auto" and I was unable to switch them to "manual" so I had to push the pin in in order to set aperture to desired size. Unfortunately, K5 wouldn't set aperture in lenses' "auto" mode because there's no in-body aperture coupling ( obviously). So, I can not manually set aperture using aperture ring while the lens is mounted and there's no way I can move "auto-man" switch on any of those lenses to "manual" position. Therefore I can only shoot wide open.... On my other Tak ( Auto 55/1:1.8) , which has M42 mount, too I can easily move the switch between "auto" and "manual" but the back of this lens looks little different: there's no semi-circular coupling sticking out that moves with aperture ring movement. Just an usual aperture pin. Is there anything wrong with both of newly acquired lenses and the only way they'd work on K5 is to push aperture pins in/ remove them ( i.e. to effectively disable auto aperture control mechanism)? Or maybe there's a secret way to set two lenses in "manual" mode so I could change aperture by simply turning the ring while lenses are mounted ?
In the picture (from left to right) : SMC Takumar 135/1:3.5
SMC Takumar 28/1:3.5
Auto - Takumar 55/1:1.8

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[elliott]

There is a "secret", there is another pin that must be pressed in to be able to switch it.

[atarget]

There is a "secret", there is another pin that must be pressed in to be able to switch it.

Thanks. For some reason original Pentax m42-pk adapter didn't depress it
I just did it now with a toothpick and everything is working as it should.
Those Taks are genuine pieces of art by the way.... Amazing vintage glass

[elliott]

That is the only annoying thing about the SMC ones, you can't switch that on the fly, they are the only ones that have that. With my M42 glass I use the switch to make it simulate a preset, compose and focus in A, flip to M to shoot.

[313 TUxedo]

There is a "secret", there is another pin that must be pressed in to be able to switch it.

Thanks so much for posting this. I never would have figured this out myself.

For some unknown reason, my just-acquired Spotmatic F body isn't pushing this pin in deep enough when I mount its lens to it, but the switch works easily when I push the pin in on the loose myself.

[grahame]

Thanks. For some reason original Pentax m42-pk adapter didn't depress it

If you have an original M42 rear cap, screw it on and you can adjust the M/A switch.