Is there life after aperture block failure?

Futax wrote:

No, it won't stop down correctly if you set it to "A" (which is the equivalent to F22 or whatever as far as your camera is concerned). That would be just the same as using a lens without an aperture ring. Just set the aperture ring to your chosen aperture (which might well be an aperture which maximises sharpness), and in Av mode it will stop down to that aperture (at least with my K-50 it will).

Since the exposure metering is done just before you take the shot, and the camera assumes the aperture is wide open (it knows no different, as the aperture ring doesn't communicate back to the camera), the camera will overexpose unless the aperture is actually set to be wide open.

So you have to use exposure compensation to counteract this. For example, if it's an F4 lens and you set the aperture ring to F8, you will need +2EV compensation.

Give it a try, and report back, because that is how my own K-50 behaves, and I'm assuming it applies to all K-50s. It'll hopefully be of help to a lot of people!:-)

I am a little bit confused as why the EV correction has to be applied. So the first thing first. As I understand, camera with the failed aperture solenoid can't control position of the aperture lever, so when you fully press the shutter button, it will move the aperture lever from fully open to fully closed. This is what happen when the lens doesn't have the aperture ring, or the Pentax-A lens has the ring in the "A" position.

Now, on a Pentax-A lens I will set the aperture ring to f:8.0 and I set the camera to the AV mode and set there f:8.0 as well. If a camera suffers from that faulty solenoid, will it be still able to close the lens to the preset position? If yes, then why to apply any EV correction? The camera will make the exposure measurement with the half pressed shutter button and at that time the lens is fully open. The camera somehow has to detect what is that fully open aperture (like f:4.0) to make a correct exposure calculations. And it knows that the actual aperture will be f:8.0 (and you have the aperture ring at the f:8.0 position already set), so camera will make that needed EV correction itself. Actually there shouldn't be any difference between in the camera/lens behaviour with a faulty and normally working aperture solenoid.  Or am I wrong?