Autofocus screwmount M42 135/2.5

Started Jun 3, 2006 | Discussions thread
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brandrx Forum Pro • Posts: 28,337
Autofocus screwmount M42 135/2.5

I was testing sometihing out with my screwmount M42 SMC Takumar 135/2.5 + the Pentax-F 1.7X AF Adapter and I thought this might be a good time to remind folks that a screwmount lens can be made to autofocus. This particular combination becomes a 230mm f4.25 autofocus lens.

What I was testing out was how this setup worked with the AF set to the OK button in the Custom menu. It seems to work better this way when using screwmount lenses with the 1.7X AF Adapter. I set the mode to Av and the AF/MF switch to AF at the camera, I select my aperture on the lens, set the Auto/Manual switch on the lens to Auto, press the OK button to focus, change the Auto/Manual switch on the lens to Manual, press the shutter release.

I forgot to mention that you need to short out the contacts on the Pentax-F 1.7X AF Adapter (between lens and adapter) with aluminum foil or very thin metal.

Below is a test pic I took with backlight and the image was quite dark, but the combo still was able to autofocus. The second pic is a 50% crop and the third pic is a 100% crop.

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Ron ~ Retired

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