Could the focusing screen be misaligned?

[MarBa]

I have a feeling that the focusing screen on my K-3 III is not properly aligned.

When I manually focus as well as I can, say on a tree in a distance, and then take the shot, the tree is not focused properly. I tried this several times and I tried to adjust the dioptric compensation but nothing helps.

If I use AF, the focus is perfect with the same lens. But I can then see that I can make it appear even sharper in the OVF by manually refocusing.

I don't experience any of this on my older K-1.

Anyone ever had a similar experience? I'm going to send the camera to a service.. but I'm interested to know if this is a common problem and to know what could be causing it. Is it the screen? Or the mirror?

Best,

M

 

[ozdean]

If this is happening you need to shim your focus screen.

Send it in under warranty.

--
Regards Dean - Capturing Creation
N.B. All my Images are Protected by Copyright

 

[MightyMike]

I have a feeling that the focusing screen on my K-3 III is not properly aligned.

When I manually focus as well as I can, say on a tree in a distance, and then take the shot, the tree is not focused properly. I tried this several times and I tried to adjust the dioptric compensation but nothing helps.

If I use AF, the focus is perfect with the same lens. But I can then see that I can make it appear even sharper in the OVF by manually refocusing.

I don't experience any of this on my older K-1.

Anyone ever had a similar experience? I'm going to send the camera to a service.. but I'm interested to know if this is a common problem and to know what could be causing it. Is it the screen? Or the mirror?

Best,

M

In film cameras with split prisms, if the photo didn't agree with the focus it was likely that the mirror was out of alignment and needed to be shimmed a little. Best choice would likely be get it serviced indeed!

 

[jonby]

Yes it sounds like the focusing screen.

I had this with a K10D. Didn't have much cash at the time, so I shimmed it myself with a couple of thin strips of electrical tape to the supporting frame. It was a pretty delicate operation, but doable with a steady hand and some tweezers. This sorted out the problem and the tape is still in place after about 13 years. Not sure I would want to risk this with a brand new K3 iii though!

First thing to check is whether it could have been knocked out of place in any way. I don't have that model, but I assume you can pull down the frame that holds it in place, check seating and push it back up. Possible this might sort out the problem.

If not, check is whether it has any adjustment built-in. Some Pentax film cameras used to have an adjustment screw for this. It's also possible the default setup includes shims, which could then be taken out to adjust in one direction.

Is it back-focusing or front-focusing when focusing manually with the screen? If it's causing you to back-focus, then the screen would need to be moved downwards (closer to the lens in the optical path). If it's front-focusing, the screen would need to move up (think I've got that right). If it's the latter, then you would add a shim. If it's the former, you'd need to remove a shim. If there aren't any, then you might be stuck.

Before you do anything though, you should make absolutely sure that the problem exists, and is consistent by careful testing. Obviously there is some user-error involved, because the screens never allow for pinpoint accuracy.

If it is indeed out of whack, then that's quite disappointing for a high-end model. Would have thought Pentax would be checking these things, especially since the viewfinder quality is something they sell the camera on.

 

[MarBa]

Yes it sounds like the focusing screen.

I had this with a K10D. Didn't have much cash at the time, so I shimmed it myself with a couple of thin strips of electrical tape to the supporting frame. It was a pretty delicate operation, but doable with a steady hand and some tweezers. This sorted out the problem and the tape is still in place after about 13 years. Not sure I would want to risk this with a brand new K3 iii though!

First thing to check is whether it could have been knocked out of place in any way. I don't have that model, but I assume you can pull down the frame that holds it in place, check seating and push it back up. Possible this might sort out the problem.

If not, check is whether it has any adjustment built-in. Some Pentax film cameras used to have an adjustment screw for this. It's also possible the default setup includes shims, which could then be taken out to adjust in one direction.

Is it back-focusing or front-focusing when focusing manually with the screen? If it's causing you to back-focus, then the screen would need to be moved downwards (closer to the lens in the optical path). If it's front-focusing, the screen would need to move up (think I've got that right). If it's the latter, then you would add a shim. If it's the former, you'd need to remove a shim. If there aren't any, then you might be stuck.

Before you do anything though, you should make absolutely sure that the problem exists, and is consistent by careful testing. Obviously there is some user-error involved, because the screens never allow for pinpoint accuracy.

If it is indeed out of whack, then that's quite disappointing for a high-end model. Would have thought Pentax would be checking these things, especially since the viewfinder quality is something they sell the camera on.

Thank you!

I will have a careful look at the focusing screen but I will not try to fix it.

Best,

M

 

[petrock]

I have a feeling that the focusing screen on my K-3 III is not properly aligned.

When I manually focus as well as I can, say on a tree in a distance, and then take the shot, the tree is not focused properly. I tried this several times and I tried to adjust the dioptric compensation but nothing helps.

If I use AF, the focus is perfect with the same lens. But I can then see that I can make it appear even sharper in the OVF by manually refocusing.

I don't experience any of this on my older K-1.

Anyone ever had a similar experience? I'm going to send the camera to a service.. but I'm interested to know if this is a common problem and to know what could be causing it. Is it the screen? Or the mirror?

Best,

M

Before you do anything, check your AF lens to see if it focuses edge-to-edge the same manually as it does in AF. I have an AF lens that does not manual-focus uniformly left edge and right edge, compared to auto-focus---the lens seems to be 'decentered'. In other words, I get good shots to both edges with AF, but not with MF.