M42 lens on a DSLR: how to stop down?

[Syb]

This may have been discussed here a thousand times already, so if it was, please point me to the thread I couldn't find myself... I have a 16mm Zenitar fisheye on a M42 mount, that I would like to use on DSLR. That is: use the aperture ring to stop down.

I have a M42 to K mount adaptor, but that does not do the trick.

Makes me wonder: is what I want, impossible or is there a trick I do not know of? There is a pin on the mount side, that - if pressed - sets the aperture. But it looks as though the pin is not moved by the camera body. Is there a way to use the lens better than just wide open?

Thanks,
Syb

[speedoo]

I'm new to this, like you. I found an explanation a few weeks back and I will try to find it for you. But as I recall, these are the steps:

1. Open the lens up wide (lowest f-stop) and focus your shot.

2. Select the f-stop you want to use.

3. With the lens aperture set, use your camera's metering to set shutter speed for proper exposure and shoot.

[Syb]

Yeah, that is the way to proceed. But selecting the desired F-stop is something else. That action (turning the ring) should be followed by a response (smaller iris in the lens). Fact is that that doesn't happen.

I found that there are M42 lenses with an Auto/Manual lever, making it possible to work with or without the stopping down pin.

My Zenitar does not have that feature. Just a pin.

When the pin is pushed in manually (off the camera), the aperture does work properly. However there is nothing in the camera body that pushes the pin.

While trying and trying all of a sudden I pushed the pin in and it did not pop back out again.

Now what a pity that is....

... my problem is solved! Stopping down is by choosing the desired f-stop. Viewfinder gets darker then. But focus was done wide open already. Problem solved! Yay!