Originally posted by mobiuspizza ...when shutter is on, the apecture diaphragm closes like an iris and retain a smaller hole for light to go in. Correct me if I am wrong. I think the size of the hole is determined by F stop settings. To be honest I cannot tell the difference for the size of the hole between F4 and F22, for both lens.
I still hope the problem is mechanical. If it is, there's a better chance you can fix it without sending it to Pentax. If it is electronic, there's not much we can do.
Here's "normal":
- When off camera, a lens that has no aperture ring has the aperture fully close (the opening is small).
- When attached to the camera, the aperture opens up fully, and closes down to the set aperture during taking the photo, and opens up again.
Now to determine if the aperture and the aperture linkage work correctly:
- Attach the lens to the camera. Set it to manual mode with a low shutter speed, e.g. 1/4 sec..
- Turn the camera so that the viewfinder faces a light source so it's easy to see the aperture opening from the front of the camera.
- On the camera, set the aperture to max (e.g. F/4).
- Hit the shutter release while looking into the front of the lens. You should see no movement of the aperture because it remains fully opened.
- Set the aperture to min (e.g. F/22).
- Hit the shutter release while looking into the front of the lens. You should see the aperture close down, then open up again at the end for the exposure.
Please report back.