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10-10-2019, 11:50 AM   #31
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QuoteOriginally posted by Qman Quote
I still think it's the lens, otherwise something would be in focus in the photo. This isn't a case of front or back focus, it's a case of no focus. I'd like to see two identical photos, one on the KS1, one on a different body, so that we can see the difference between cameras.
So apparently I ask for thoughts on an issue I'm having and I have to keep defending myself all the time.

So the K 50 1.2 is kind of soft wide open. But if you look closely you will find a brown dot that is in focus. The number 70 at the bottom is in focus as well but since it's white on black it shows aberrations when pixel peeping.

Here is the brown in focus detail I'm talking about. Even though it's right next to the number 30 that was in focus in the viewfinder, it's actually quite in front because remember, the globe is round...



10-10-2019, 12:01 PM   #32
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QuoteOriginally posted by pschlute Quote
Christian (OP) . This is a very, very, edge case. You really need to provide unequivocal evidence to prove your point here. It's not that folk don't believe you, but just its very unlikely.
Well it does sound like you don't believe me, right?...

Here's the same lens on the K10D with some in-focus areas at f/1.2. 10MP instead of 20MP so it will look sharper wide open.





I did several tests with the K-S1 and the issue is reproduceable. I created this thread to know if others had the same issue and how they dealt with it because I hadn't thought of doing the diopter adjustment. I'm not sure I like to come here and ask for help and then repeatedly have to keep defending myself. Maybe now that I have somewhat of a workaround this thread can be closed, because I won't defend myself any further.
10-10-2019, 12:11 PM   #33
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***a little humor*** Its all I got at this point, sorry.

Wait the earth is spinning and the brown spot was next to the 30 but the afc in manual focus moved with the brown spot, clearly the afc is on the wrong part
10-10-2019, 12:11 PM   #34
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QuoteOriginally posted by ChristianRock Quote
Well it does sound like you don't believe me, right?
You misunderstand me. What you are suggesting is very improbable. That is all. It means you need to be providing more detailed evidence of the problem.

10-10-2019, 12:17 PM - 1 Like   #35
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QuoteOriginally posted by pschlute Quote
You misunderstand me. What you are suggesting is very improbable. That is all. It means you need to be providing more detailed evidence of the problem.
Sorry, I came here for help, not to be put on trial. I think I provided evidence that the lens isn't broken and gave a visual of what my issue is. I also found a workable solution for now.

Last edited by ChristianRock; 10-10-2019 at 12:39 PM.
10-10-2019, 12:43 PM   #36
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QuoteOriginally posted by ChristianRock Quote
So the K 50 1.2 is kind of soft wide open.
Enter the elephant into the room. Remembering the above, lets factor in a few other points:
  • Evaluating at full resolution on a 20Mpx capture ups the ante significantly over doing the same on the K10D. Even slight missed focus is all the more obvious on the newer camera.
  • The stock focus screen, on account of its brightness treatment, exaggerates DOF to somewhere in the neighborhood of f/4.0.* As a result, precision when attempting fine focus may be rather poor with an f/1.2 lens to the extent that missed focus is likely to be the norm rather than the exception when evaluated at full resolution and maximum aperture.
  • Given the above point and the softness of the lens wide open, user technique may easily emulate front or back focus while trying to nail focus on mush.
  • Fine focus for an f/1.2 capture is very difficult, even with a split image focus aide and perfect screen calibration
  • Focus confirmation with a fast lens generally provides a range of focus, within which the green hexagon remains lit. Only one point in that range is actually in focus. The rest is merely where PDAF can't tell if it is OOF.
  • Given that there are very few subjects where shooting at f/1.2 or even f/1.4 is desirable, it may be best to be aware that a certain softness at those apertures is to be expected.
  • Attempting calibrate the stock focus screen is intrinsically difficult
The takeaway here is that there is no blame to assign and that being able to avoid the optical viewfinder using magnified live view is a wonderful asset when working on-tripod and using DOF for subject isolation.


Steve

* This may be demonstrated with a fast manual aperture lens, noting that both viewfinder brightness and apparent DOF stay the same until about f/4.

Last edited by stevebrot; 10-10-2019 at 12:49 PM.
10-10-2019, 12:49 PM - 2 Likes   #37
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I think everyone is just trying to help, not put you on trial. I'm a mechanical engineer. If I'm working on a technical problem I know from experience that if the solution isn't obvious then a thorough look at all aspects is required. That means going over details that have previously been assumed to be correct. It isn't personal, it's just how problems need to be solved. Often there is something that's been overlooked, and the solution is found.
10-10-2019, 12:54 PM   #38
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QuoteOriginally posted by stevebrot Quote
Enter the elephant into the room. Remembering the above, lets factor in a few other points:
  • Evaluating at full resolution on a 20Mpx capture ups the ante significantly over doing the same on the K10D. Even slight missed focus is all the more obvious on the newer camera.
  • The stock focus screen, on account of its brightness treatment, exaggerates DOF to somewhere in the neighborhood of f/4.0.* As a result, precision when attempting fine focus may be rather poor with an f/1.2 lens to the extent that missed focus is likely to be the norm rather than the exception when evaluated at full resolution and maximum aperture.
  • Given the above point and the softness of the lens wide open, user technique may easily emulate front or back focus while trying to nail focus on mush.
  • Fine focus for an f/1.2 capture is very difficult, even with a split image focus aide and perfect screen calibration
  • Focus confirmation with a fast lens generally provides a range of focus, within which the green hexagon remains lit. Only one point in that range is actually in focus. The rest is merely where PDAF can't tell if it is OOF.
  • Given that there are very few subjects where shooting at f/1.2 or even f/1.4 is desirable, it may be best to be aware that a certain softness at those apertures is to be expected.
  • Attempting calibrate the stock focus screen is intrinsically difficult
The takeaway here is that there is no blame to assign and that magnified live view is a wonderful asset when working on-tripod and using DOF for subject isolation.


Steve

* This may be demonstrated with a fast manual aperture lens, noting that both viewfinder brightness and apparent DOF stay the same until about f/4.
Well, I don't have that issue with the K-50 which is 16MP. But with the K-S1 I was able to consistently have the focus shifting to the same place in front every time in several tests with different subjects. And now I'm consistently able to get much closer focus having changed the diopter setting. If it was just an issue of the lens being difficult to focus, I would not have the exact same result every time. And remember that while the K 50 1.2 looks soft when pixel peeping at 20MP, the viewfinder experience is about the same between K10D, K-50 and K-S1.

I probably learned a LOT from focusing my Rikenon XR 50 1.4 over the years. That lens wide open is about as soft as melted butter. And I still managed to get the focus right every time I used it.

10-10-2019, 12:57 PM   #39
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QuoteOriginally posted by ChristianRock Quote
Well it does sound like you don't believe me, right?...

Here's the same lens on the K10D with some in-focus areas at f/1.2. 10MP instead of 20MP so it will look sharper wide open.





I did several tests with the K-S1 and the issue is reproduceable. I created this thread to know if others had the same issue and how they dealt with it because I hadn't thought of doing the diopter adjustment. I'm not sure I like to come here and ask for help and then repeatedly have to keep defending myself. Maybe now that I have somewhat of a workaround this thread can be closed, because I won't defend myself any further.
Do you have pictures of the same subject with the k10d?
10-10-2019, 01:01 PM - 1 Like   #40
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QuoteOriginally posted by stevebrot Quote
Enter the elephant into the room. Remembering the above, lets factor in a few other points:[LIST][*]Evaluating at full resolution on a 20Mpx capture ups the ante significantly over doing the same on the K10D. Even slight missed focus is all the more obvious on the newer camera.[*]The stock focus screen, on account of its brightness treatment, exaggerates DOF to somewhere in the neighborhood of f/4.0.* As a result, precision when attempting fine focus may be rather poor with an f/1.2 lens to the extent that missed focus is likely to be the norm rather than the exception when evaluated at full resolution and maximum aperture.[*]Given the above point and the softness of the lens wide open, user technique may easily emulate front or back focus while trying to nail focus on mush.[*]Fine focus for an f/1.2 capture is very difficult, even with a split image focus aide and perfect screen calibration[*]Focus confirmation with a fast lens generally provides a range of focus, within which the green hexagon remains lit. Only one point in that range is actually in focus. The rest is merely where PDAF can't tell if it is OOF.
[
Steve
.
to the first point I quote here. But only that lens even when at f2.8? (Stated somewhere up thread.)
point 2. You think the different focus screen of the ks1 could be the culprit?
point 3. Then why even at 2.8 only on that lens?
point 4. again even at f2.8?
point 5 presents a test. What if focus from close and focus from infinity both end up front focusing? And makes me wonder about the focus throw on the lens. how long and smooth is it? perhaps a mirror slap unsettles it and a more pronounced mirror slap on the ks1?
10-10-2019, 01:10 PM   #41
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QuoteOriginally posted by ZombieArmy Quote
Do you have pictures of the same subject with the k10d?
I think I still have some on the K-50 that is at home but I think I found a workable solution (as mentioned several times) so I think I'm done with documenting this issue...

I came to the conclusion that it's just one of those things you have to accept that it's the way things are. Now that I think of it, my SMC-F focuses perfectly on the K10D and K-S1 but required a +9 on my K-50. Why? I have no idea. My DA 35 2.4 also required adjustment on the K-50 but the Sigma 30 1.4 doesn't require adjustment on any of the cameras. I just did the one-lens adjustment for those AF lenses that needed and got on... now my pictures are in focus. I just didn't really know what to do about the problem with the K 50 1.2 when I started this thread.
10-11-2019, 03:01 AM   #42
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QuoteOriginally posted by dlh Quote
When you add shims, they go between the focusing screen and the prism - i.e. they decrease the distance between the focusing screen and the mirror, which moves the plane of focus forward. If the camera is already front-focusing, adding shims will only make it worse.
Bear in mind that the focusing screen may be shimmed when bought (all SLRs should go through a process of checking the accuracy of focusing and shimming if necessary before they leave the factory) so "shimming" can mean adding or taking away, as required.

My K200D used to focus perfectly (checked with an 85/2 wide open) with a Katzeye installed and no extra shims added then one day it was off and I had to shim it to get the same accuracy back. This was despite no bumps or fiddling of any kind, which just goes to show how sensitive these things are.
10-11-2019, 04:44 AM   #43
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QuoteOriginally posted by ChristianRock Quote
...

I think in your case - correct me if I'm mistaken - where the issue is consistent and happens to all your manual focus lenses, you could use the "For All" fine focus adjustment that Medex mentioned in this thread. I've used this and it works well. Now if every lens is giving you a different result and you change lenses a lot, things might be a bit more difficult...
Except for the fact that I'm not using autofocus at all. So "lens calibration" has nothing to do with my problem. I wish it did, but it's a matter of physical distance between the focusing screen and the prism.
10-11-2019, 06:14 AM - 1 Like   #44
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QuoteOriginally posted by dlh Quote
Except for the fact that I'm not using autofocus at all. So "lens calibration" has nothing to do with my problem. I wish it did, but it's a matter of physical distance between the focusing screen and the prism.
But if you use the "Apply All" setting in the AF Fine Tuning, it applies even to manual focus lenses! I used it first with my K20D which required AF adjustment of -1 for all lenses. I've also tried it with my K-S1. It works!
10-11-2019, 07:23 AM   #45
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QuoteOriginally posted by dlh Quote
Except for the fact that I'm not using autofocus at all.
In that case you could exchange the plane focus screen with a spilt screen. I havn't done it myself but I think I have read it is possible.

QuoteOriginally posted by dlh Quote
So "lens calibration" has nothing to do with my problem.
For a full manual approach and fast lenses wide open it doesn't help much, but focus confirmation (which is influenced by lens calibration) is still possible with manual lenses, too
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