[AlfredD]

I seem to be having an optical preview issue with my K10D. I am not sure that it ever worked right. I am familiar with optical previews on film cameras, which we used to call the the Depth of Field Preview. On my K10D, no matter where I set the camera, I can never get an optical preview. I have set and reset the C settings and worked with the digital preview fine, but the optical preview doesn't seem to work. I will set up an exposure in a bright situation at ISO 1600, with an f-stop of 22-32, and use the optical prieview. I would expect to see the field darken and the DOF change as the arpeture changed in the lens. I seem to hear the sound of something moving in the lens, but no change occurs in the field. I am using 2 lenses, Pentax-DA 18-55 and a Pentax FAJ 75-300. Has anyone else come across this. Is there a fix?

[Adam]

And you're using the power button to accomplish this?

[SOldBear]

Some more details may help trouble shooting:

1. Did optical preview use to work, and now stops working? Or did it never worked before?

2. Mount the Pentax DA 18-55 on to the camera, on the camera, set the aperture at the largest (e.g. F/3.5). Shine a light into the viewfinder, while looking into the lens from the front, change the aperture setting to the smallest (e.g. F/22), do you see the aperture blades moving?

3. Mount the Pentax DA 18-55 on to the camera, on the camera, set the aperture at the smallest (e.g. F/22). Shine a light into the viewfinder, while looking into the lens from the front, activate optical preview, do you see the aperture blades moving?

[AlfredD]

Thanks for the testing advice. I should have thought of that myself.
1. I'm not sure it ever worked, but I can't be sure about that.
2. The apeture doesn't change at when changing the f-stop. I also wouldn't expect it to, am I correct?
3. The apeture doesn't change when activating the optical preview on the power button.

I'm thinking that something is wrong with the mechanisms. I hear a servo moving when I apply the switch, but no apeture change occurs. It still takes pictures generally properly exposed.

[SOldBear]

2. The apeture doesn't change at when changing the f-stop. I also wouldn't expect it to, am I correct?

That's correct. The aperture should remain at the largest, regardless of the aperture setting on the camera body.

Does the viewfinder appear dimmer than what it should be? (I know, it's difficult to tell if you have no other camera body to compare to. But the viewfinder should be bright enough for you to focus manually).

Set the camera to manual, with the smallest aperture (e.g. f/22), and a low shutter speed (e.g. 1/4 sec). Look into the lens and hit the shutter release. Do you see the aperture blades moving?