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10-09-2019, 10:32 AM   #1
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Manual focus lens front focusing results on only one of your bodies?

Hi, I'm not sure I've seen this before... but have you had a lens that is manual focus, yet it consistently front focuses on only one of your bodies?

I tested my K 50mm f/1.2 on my K-S1 and it severely front focuses while on the viewfinder I see perfect focus. I also get focus confirmation!

The same lens will focus perfectly on my K-50 and K10D, so I'm very puzzled because I wanted to see how it performs on the K-S1. Other lenses work fine in the K-S1, I just tested some.

In the test below, I get perfect viewfinder focus (and focus confirmation) on the number 40. If this was my Rikenon P 50 1.4, the picture would show the focus right on the money...





Has anyone seen anything similar?

10-09-2019, 10:57 AM   #2
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YES!!! though it isn't the lens, it's the camera. I bought a K-1 a while back, and I've been struggling with focusing the whole time I've had it. I've been pretty much an exclusively manual focus kind of guy, but had problems (compounded by a couple of bad lenses) with focusing the entire time. So dealing with the lenses got me into the calibration thing, and I'd been doing that for a while, and then realized the autofocus was wonky. I sent it to Precision and they got the autofocus thing nailed under warranty and right quick. Now I discover that camera front-focuses in manual focus only mode. Only it took me so long to figure it out that both the original warranty period and the fix-it warranty period had elapsed.* They want another four hundred bucks or so to fix it right this time. I'm thinking that since most people don't even know HOW to manually focus, Pentax treats people who do want to focus manually as irrelevant to their business model. I'm being forced to modify my practices to suit the changes in technology. So maybe one of them Fujifilm mirrorless cameras with the "electronic viewfinder" will be my next purchase. The optical viewfinder was one of my main reasons for getting the K-1, and it turns out to be pretty much useless.

* As a technical legal matter, a "warranty" is not a period of time in which you can get a product fixed for free, it's a promise made at the time of sale. So no question Pentax is in breach of warranty, and there's a four year statute of limitations on that claim where I live. Only problem is that it's a hassle to go down to the courthouse to file it and pay the filing fee to the clerk. Still thinking. About that AND the lens problems.
10-09-2019, 11:06 AM   #3
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QuoteOriginally posted by ChristianRock Quote
I see perfect focus. I also get focus confirmation!
QuoteOriginally posted by ChristianRock Quote
I tested my K 50mm f/1.2 on my K-S1 and it severely front focuses while on the viewfinder I see perfect focus. I also get focus confirmation!
Not sure what you are saying ? It is a manual focus lens. Forget about focus conformation or adjust it if it is out. You have AF/FA menu for that.

Nothing is in focus in your submitted picture
10-09-2019, 11:08 AM   #4
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QuoteOriginally posted by dlh Quote
YES!!! though it isn't the lens, it's the camera. I bought a K-1 a while back, and I've been struggling with focusing the whole time I've had it. I've been pretty much an exclusively manual focus kind of guy, but had problems (compounded by a couple of bad lenses) with focusing the entire time. So dealing with the lenses got me into the calibration thing, and I'd been doing that for a while, and then realized the autofocus was wonky. I sent it to Precision and they got the autofocus thing nailed under warranty and right quick. Now I discover that camera front-focuses in manual focus only mode. Only it took me so long to figure it out that both the original warranty period and the fix-it warranty period had elapsed.* They want another four hundred bucks or so to fix it right this time. I'm thinking that since most people don't even know HOW to manually focus, Pentax treats people who do want to focus manually as irrelevant to their business model. I'm being forced to modify my practices to suit the changes in technology. So maybe one of them Fujifilm mirrorless cameras with the "electronic viewfinder" will be my next purchase. The optical viewfinder was one of my main reasons for getting the K-1, and it turns out to be pretty much useless.

* As a technical legal matter, a "warranty" is not a period of time in which you can get a product fixed for free, it's a promise made at the time of sale. So no question Pentax is in breach of warranty, and there's a four year statute of limitations on that claim where I live. Only problem is that it's a hassle to go down to the courthouse to file it and pay the filing fee to the clerk. Still thinking. About that AND the lens problems.
But it sounds like it's affecting all of your lenses, no? With mine, it's only one lens. The results with other lenses are good.

If it's happening to all your manual lenses - I saw a thread here saying there's a couple of screws that show up when you remove the camera's bottom plate, and you can manually move the whole AF mechanism with them. It would probably mess up with your AF adjustment though, if you tried that.

Here's that thread if you're instersted: AF adjustment on K-7 (maybe K-5 too) - PentaxForums.com

10-09-2019, 11:09 AM   #5
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QuoteOriginally posted by pschlute Quote
Not sure what you are saying ? It is a manual focus lens. Forget about focus conformation or adjust it if it is out.
I see where the focus is in the viewfinder. Then when I press the shutter, the focus is elsewhere.
10-09-2019, 11:17 AM   #6
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Your camera/lens combination might needs some focus adjustment. But this will maddle with your Rikkenon P setting, because it's not a Pentax-F or newer lens you can't adjust for this lens alone.
I might be mistaken (I don't usually shoot that wide, so I didn't care much about the AF-sensor abilities in the OVF) but I think the centre AF-point is accurate for f2.8 or higher, and those on the side for f5.6 or higher/narrower. So shooting wide open might exceeds the AF-point abilities of the camera. Also the globe seems to be better in focus than the scale (at 40) so maybe your focus point was too big and hit the globe instead, have you shot multible testpictures to confirm your findings?

Last edited by othar; 10-09-2019 at 11:23 AM.
10-09-2019, 11:25 AM   #7
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QuoteOriginally posted by othar Quote
Your camera/lens combination might needs some focus adjustment. But this will maddle with your Rikkenon P setting, because it's not a Pentax-F or newer lens you can't adjust for this lens alone.
I might be mistaken (I don't usually shoot that wide, so I didn't care much about the AF-sensor abilities in the OVF) but I think the centre AF-point is accurate for f2.8 or higher, and those on the side for f5.6 or higher/narrower. So shooting wide open might exceeds the AF-point abilities of the camera.
I have many fast (f/2.8 and faster) lenses, so adjusting for the K 50 1.2 would break everything else.

Ok, so let's forget the focus confirmation... the fact that I'm seeing something sharply in focus in the viewfinder, and yet the picture shows it completely blurry, seems to be way beyond any focus sensor sensibility.

I *can* focus using live view, and that works, but I'd rather use the viewfinder...
10-09-2019, 11:44 AM - 1 Like   #8
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QuoteOriginally posted by ChristianRock Quote
Ok, so let's forget the focus confirmation... the fact that I'm seeing something sharply in focus in the viewfinder
That is strange indeed.
For the time beeing you could set your visual accuraty correction on the OVF accordingly, but that can be a hassle too when changing lenses. (I have to change this setting regularly because my eyesight varies depending on how many hours I spend infront of a computer monitor or behind a book per week opposing going hiking or mountaineering)

10-09-2019, 11:50 AM   #9
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What happens if you focus using focus peaking in live view? Does that show anything in focus? What's the chance that the OVF view actually isn't focused, but it's difficult to see. Perhaps what you're actually seeing is the best focus possible, but not something that is actually in focus?
As mentioned previously, nothing is in focus in that photo. The ring with the numbers is at an angle to the camera. The edge of the ring that's closer to the camera is clearly ahead of the focus plane. The other side of the ring is clearly behind the focal plane. The 80 or 90 at the top should therefore be in focus, but it isn't. It looks to me like it's an issue with the lens. Something isn't right internally. Perhaps a lens element is out of alignment.

---------- Post added 10-09-19 at 11:52 AM ----------

I just noticed that you said the lens focuses just fine on other cameras, so I'm officially stumped...
10-09-2019, 11:58 AM   #10
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QuoteOriginally posted by Qman Quote
The 80 or 90 at the top should therefore be in focus, but it isn't.
I am not so sure about that, I think the focus is somewhere around 90 at f1.2 it's just too narrow to say with certainty without seeing the full resolution.
10-09-2019, 12:28 PM   #11
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Is this only at 1.2 or at 2.8 also. I thought ovf is only rated for 2.8. Perhaps the lens being soft at 1.2 making lines harder to pin down + accuracy below 2.8 together?
When testing my 55-300 plm I also noticed a drop in sharpness from what I see in the ovf to what I get on my ks2. The difference is like seeing a line on an eye chart to seeing enough to guess, h,b are a guess but o, n is not.
10-09-2019, 12:36 PM   #12
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QuoteOriginally posted by Qman Quote
What happens if you focus using focus peaking in live view? Does that show anything in focus? What's the chance that the OVF view actually isn't focused, but it's difficult to see. Perhaps what you're actually seeing is the best focus possible, but not something that is actually in focus?
As mentioned previously, nothing is in focus in that photo. The ring with the numbers is at an angle to the camera. The edge of the ring that's closer to the camera is clearly ahead of the focus plane. The other side of the ring is clearly behind the focal plane. The 80 or 90 at the top should therefore be in focus, but it isn't. It looks to me like it's an issue with the lens. Something isn't right internally. Perhaps a lens element is out of alignment.

---------- Post added 10-09-19 at 11:52 AM ----------

I just noticed that you said the lens focuses just fine on other cameras, so I'm officially stumped...
It works well in live view, I just don't like it much. But I might have to live with it, or use the lens mostly on the K-50.

I just realized something that I want to try next. I can try and find a position with the diopter where the viewfinder position would match the actual focus. I think it's worth trying I just have to remember to put it back to the center when I'm done...

QuoteOriginally posted by swanlefitte Quote
Is this only at 1.2 or at 2.8 also. I thought ovf is only rated for 2.8. Perhaps the lens being soft at 1.2 making lines harder to pin down + accuracy below 2.8 together?
When testing my 55-300 plm I also noticed a drop in sharpness from what I see in the ovf to what I get on my ks2. The difference is like seeing a line on an eye chart to seeing enough to guess, h,b are a guess but o, n is not.
I figured people would say that, which is why I posted the pictures you can tell where the focus is with the crop even if it is indeed a bit soft.

And it's still severely out of focus at f2 and quite a bit out of focus at f2.8. But it depends on the distance as well.
10-09-2019, 01:19 PM   #13
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So I'm quite happy to report that I am able to get better results by moving the diopter quite a bit to the left. Not perfect yet, but 2/3 of the way there. If I turn the diopter all the way to the left, I feel the image quality suffers, so that is why I stopped where I did.
10-09-2019, 02:01 PM   #14
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Interesting. If you do a universal focus adjustment I wonder how far you need to go. Would be a pain to do this every time you use the lens. It would be interesting to see how the adjustment corresponds to the diopter.
10-09-2019, 02:14 PM   #15
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QuoteOriginally posted by ChristianRock Quote
I see where the focus is in the viewfinder. Then when I press the shutter, the focus is elsewhere.
I would not be concerned about focus confirm. Its ability to detect OOF is the same with an f/2.8 lens as with your f/1.2.

There is a problem with either the focus screen shimming or the mirror alignment. If the latter, auto focus would also be affected. I would also double check that the viewfinder diopter is right for your eyes; it is unlikely to be the cause, but no harm trying. Addendum: I just saw your note regarding the diopter adjust. FWIW, Using an f/1.2 ups the game significantly in terms of focus difficulty. Ideally, one would have the help of a split image finder.


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