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06-03-2014, 10:06 AM   #1
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Focus is off-center - what am I doing wrong?

I have a relatively new K-50, my first SLR (D or otherwise). Fairly often, the best focus is to the lower left of where I intend -- sometimes more to the left, sometimes more below. I put the subject of interest in the center of the focus bracket in the viewfinder (also where the red dot appears, which I understand is not necessarily indicative).

This happens with all my lenses - manual (two lenses) and AF (two kit lens and one other).

Because these are hand-held, I'm not complaining about a general lack of sharp focus. The issue is that an unintended portion of the subject is in focus in a consistent way. With the lens I used today, it was usually to the lower left and right of center, not more to the left as with my other lenses.

I searched this site and one thread I found seemed to conclude that such a camera needed repair. I'm guessing there's something I can do with the settings first since I could have inadvertently made this happen. I'm still learning about the settings.

Samples below are all with a Pentax-M 100mm macro. My target should be fairly obvious. This happens with other types of photos, but I had these today. It's less obvious in the flower (and I was aiming for the center), but I included it since it's one I took from above instead of trying to get the camera low enough for a subject near the ground.

The blue one was cropped to cut out some of the right and top sides, but the others are as they came from the camera.

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Last edited by EllenJ; 06-03-2014 at 10:14 AM.
06-03-2014, 10:26 AM   #2
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Ellen,
I have the K50 as well, and although I have never had that problem, I definitely play with the focus points before taking macro shots. It should be on the first page in the menu section of your camera. You should use the focus points in the center. When you use all 11 focus points, it will confuse the camera somewhat. What you are essentially asking the camera to do when you choose the focus points is to only focus on the middle points. That has always worked for me. The other thing you can do, if you do not feel comfortable, is use the Scene mode, and then Maco mode. that may help you sharpening the subject. I do have one question......What lens are you using for these shots?
06-03-2014, 10:50 AM   #3
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Two quick things.

1 Do you wear glasses?

2 Could you take a shot of a wall - brick ideally and if you have one, using a tripod - with you square to the wall, and post it here?

Q1 is intended to establish whether there's something with the way you use the viewfinder. Q2 is intended to establish whether the sensor is misaligned.
06-03-2014, 11:30 AM   #4
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Thanks, Wisenhymer. Good reminder about that setting, which I changed a while ago.

QuoteOriginally posted by JohnX Quote
Two quick things.

1 Do you wear glasses?

2 Could you take a shot of a wall - brick ideally and if you have one, using a tripod - with you square to the wall, and post it here?

Q1 is intended to establish whether there's something with the way you use the viewfinder. Q2 is intended to establish whether the sensor is misaligned.

THE REPLY BELOW WAS EDITED THE NEXT DAY:

1. Yes. I have separate glasses for near-mid-distance and I usually wear the computer (mid-range) glasses. I can also see near and mid-range without glasses because my cataract surgery resulted in those two corrections.

2. I am going to replace the photo and am deleting the original now to avoid clutter. I hope that's okay.

I appreciate the help.


Last edited by EllenJ; 06-04-2014 at 06:08 AM.
06-03-2014, 11:37 AM - 1 Like   #5
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Do you happen to rely on the focus confirmation with manual lenses ? That beep and green hexagon in the viewfinder ? If so then your AF system might be front or back focusing which means that it will indicate the sharp image little bit before or after the intended target.
The fact that problem persists with both manual and AF lenses tells me that this might be the case !
Probably easy to resolve with focusing adjustments - all doable in camera. Otherwise if you rely on mat field of the focusing screen - then it might be not calibrated properly - happened earlier and happens all the time. For manual focusing the focusing screen must be calibrated with utmost care and accuracy to provide you with any usable measure of sharpness .
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06-03-2014, 11:45 AM   #6
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QuoteOriginally posted by manntax Quote
Do you happen to rely on the focus confirmation with manual lenses ? That beep and green hexagon in the viewfinder ? If so then your AF system might be front or back focusing which means that it will indicate the sharp image little bit before or after the intended target...
Makes sense, but I don't rely on it. However, I've noticed that it seems to agree with my attempt to focus without using it.

Also, about 90% of the time I use the viewfinder rather than the LV.

Thanks.
06-03-2014, 12:00 PM   #7
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I know you probably have changed this Ellen. But are you certain that you change the setting in the beginning? When you turn the camera on? It will usually ask you how many millimeters the lens is. I pretty much have the A version of the same lens you are using. Take a look at some of the pics I just took with the 100MM F4
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06-03-2014, 12:09 PM   #8
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QuoteOriginally posted by Wisenhymer Quote
I know you probably have changed this Ellen. But are you certain that you change the setting in the beginning? When you turn the camera on? It will usually ask you how many millimeters the lens is...
Yes, I did that.

I neglected to mention the current lens is F4, like yours. Thanks for the photos!


Last edited by EllenJ; 06-03-2014 at 12:17 PM.
06-03-2014, 12:12 PM   #9
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It could definitely just be a bad example of the lens. Although I never use the focus lock, as it is not as dependable as the new k mount AF lenses, I tend to rely on my eye to make sure the pics are sharp. Anyway, that is the way your pics should look (Above) I feel as though the 100MM F4 is a VERY sharp lens for a 1:2 focus.
06-03-2014, 06:55 PM   #10
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How would you rate the sharpness here? Unfortunately, I can't say where I intended to focus for this one, but with this new test subject, I can keep track next time by using the numbers. Given the shape, I assumed something would be sharp if I tried to focus. I'd like to think getting a sharp image is possible with this lens -- Pentax-M 100mm f4. Used a tripod and a separate light source, no flash (mostly because it hasn't done well at closer than a few feet).

The first camera they sent was defective, so I try to rule out camera problems when something goes wrong.
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06-03-2014, 07:24 PM   #11
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QuoteOriginally posted by EllenJ Quote
...
Because these are hand-held, I'm not complaining about a general lack of sharp focus. The issue is that an unintended portion of the subject is in focus in a consistent way. With the lens I used today, it was usually to the lower left and right of center, not more to the left as with my other lenses.
...
Not sure I see the problem with the three images you posted, especially the spider ones. Yes the leaf and fabric are in focus in the lower part but the spiders also seem pretty much sharp. If you combine the very narrow depth of field in macro photos with the folds in the fabric or the leaves at different distances then the focus can be on the spiders but also on foreground objects because they are at the same distance to the lens.
06-03-2014, 10:10 PM - 1 Like   #12
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I notice there are already suggestions on focus points, which is what I was thinking, right up until I saw the lens. The only active point with any manual focus lens is the center. It's useful to remember for AF lenses but not for this lens.

Handholding might be part of the problem. Sometimes you might unintentionally rock or tilt the camera when you shoot. It might not be noticeable at regular distances, but close up magnifies these errors.

I like to use lines of text to see if the sensor and viewfinder are seeing the same thing. A flat paper with text on it is a good subject. Set up the camera on a tripod so it's pointed at a 45 degree angle to the paper. Ideally only one line of text is in focus. I have to tape the paper to the floor, because inevitably I get it almost right and the paper moves. Anyway, you can manually focus on one line, then take a shot with the lens wide open and see if you got the same line in focus in the shot. You can also use live view, focus peaking, etc. Everything should agree. (The reason for text is that I always remember what line I want in focus, but I forget numbers on a ruler or marks on a test chart.)
06-04-2014, 03:15 AM - 1 Like   #13
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Just as a side note, the focus points were off-center for my old K7. It was just below the lower left of the etched circle. The etched glass was correct, as far as I could tell, and the red-dot was in the correct spot. Just the auto focus point did not match up.
It was easy to consistently compensate for, so I didn't feel it was worth having the camera in repair for eight weeks to fix.

I would definitely use a small black dot on white paper to try to determine if the problem is with a specific lens, with the camera, a combination, etc...

Remember also, that the auto-focus points are not points. They are small areas. If you use auto-focus, the camera may simply be stupid sometimes and not know what it is you want to focus on.
06-04-2014, 03:38 AM - 1 Like   #14
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In looking at the photos and comments I think the issue is that with a macro lens depths of field is shallow and this creates part of the problem, the other part is that with macro focus is so dependant on distance that slight forward and back movement while shooting will drift the focus away from the intended target. This is the one axis that shake reduction canot compensate for
06-04-2014, 04:52 AM   #15
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Back to the shot of a brick wall, could you repeat this please but include more in the frame?

If the wall with wooded planks is all that's immediately available, could you try to include 6-8 planks running horizontally?

The idea is we're looking for lens aberrations.

If you are truly square to the wall when you take the shot then with the centre of the shot in focus the focus at the top compared of the shot to the bottom should be consistent (be it in or out of focus compared to the centre).

With regard to wearing glasses, you need to consider that when you focus on the image shown on the focus screen the eye-piece optics are designed so that the screen itself is at an effective distance of around 1 metre, so you should wear glasses with a prescription to suit reading a book or computer screen in order to focus well on the screen image.

Last edited by JohnX; 06-04-2014 at 04:58 AM.
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