Try another lens perhaps and make sure it is indeed the camera. Then either use the modes that work, get it fixed, or, probably buy another from eBay for less than the cost of a repair.

When you say you would like a video section, what exactly did you have in mind that would be needed?

Yes. Suppose we use Av, as the aperture is changed the speed should change to compensate. You change the aperture by turning the aperture ring. Set the aperture ring to "A" and now the shutter speed can be set and the aperture will change with varying light levels, and of course also if the shutter speed is altered.

Set the aperture ring to A and the body to AUTO and you are in program mode.

And so on. You're not forgetting that the aperture ring is an active item on these cameras by any chance?

Trying to think of something simple leads me to taking the two images and dragging one into the other. Reduce the opacity of the top layer so you can be sure that the two images are excatly aligned. You can put the opacity back to 100% to work on.

Then use the eraser tool to remove the unwanted parts of the top image. You can selct a hard or soft edged brush as appropriate. Don't forget to zoom in on detail - you can go right down to pixel level if you want and then no-one will tell what you have done. If you have the patience....

Finally flatten the image and save.

The Pentax is a very fine lens. If you ever came to re-sell it then it would hold its value much better than the Sigma. Witness the way Samsung versions of Pentax lenses do not sell as well as Pentax ones, even though identical.

Apart from that the reasons for staying with marque lenses are well known.

It's great to see old friends returning to the forum. Welcome back guys!

The first thing to try is cleaning the camera and lens contacts with a soft cloth. Then reseat the lens and see if the problem has cleared.

There is little difference. On the one hand I would make the best print I could in the darkroom by cropping, adjusting contast and brightness, burning and dodging, and sometimes combining images. Now I do the same in Photoshop.

One useful difference is, with the exception of polarisers, I now apply filters after the shot is taken.

OK, if you set a wide aperture (small number such as f2.8, f4, etc.) and focus on something then very little in front and behind the subject will be sharp. This is shallow depth of field.

If you set a small aperture (big number such as f11, f16, etc.) then much more will be in focus in front of and behind the subject. This is increasing your depth of field.

Example of wide aperture: A close portrait with the background out of focus emphasises the subject.

Example of maximising depth of field: A landscape with everything sharp from very close right to the horizon.

Hope that helps without complicating matters too much!

Welcome home!