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09-18-2019, 01:15 AM   #1
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Af questions

Hi guys, just joined, greetings from Italy.
I have a frustrating situation with af on my new KP. I have followed every possible suggestion, see list below, just cannot manage to get perfectly sharp images, I think about 20% are tack on, the rest slightly off perfect focus if zoomed. I usually shoot travel, landscape or street, at times candid unposed portraits. I am not trying to shoot hockey games!
I always use afs, back button focus, spot focus, prefer aperture priority usually 8 or 11.
If low light use tripod, Manual mode, live view, 2 sec timer, often high iso as well. I have even resorted to mirror block to avoid vibrations but no matter what I do the focus is off. It happens even in bright light situations, although higher percentage are good. It doesn't focus on the wrong area like background for instance, it just doesn't focus perfectly. I recently read about fine tuning lenses, which I didn't know about, could this be the solution? Manual focus is not an option because my eyesight is simply not acute enough to identify perfect focus.
I am tempted either to throw the camera off the top of the mountain, or jump off myself! What am I doing wrong?

09-18-2019, 01:34 AM - 1 Like   #2
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Hello and welcome to the forums

Would it be possible to post photos demonstrating the issue? Ideally, the full photo resized to fit here, along with a 100% crop of the subject you focused on, and settings or EXIF data. Plus, the same for one of your photos where the focus was accurate. Seeing actual photos will help us to determine if it's a focus, shutter or motion blur issue, or something else.

AF fine tuning can be important when shooting through the optical viewfinder, but is irrelevant in Live View where contrast detect via the sensor is used.

Last edited by BigMackCam; 09-18-2019 at 02:11 AM.
09-18-2019, 03:52 AM   #3
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Welcome from Rome, It.

Post your examples as suggested above. There are a ton of folks that can offer advice or suggestions.

-dave
09-18-2019, 05:44 AM - 1 Like   #4
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QuoteOriginally posted by Jnm Quote
I recently read about fine tuning lenses, which I didn't know about, could this be the solution?
Yes. This would be the first thing I would try. You need to do it with every AF lens before using it.

09-18-2019, 05:52 AM   #5
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QuoteOriginally posted by Jnm Quote
I always use afs, back button focus, spot focus, prefer aperture priority usually 8 or 11.
If low light use tripod, Manual mode, live view, 2 sec timer, often high iso as well. I have even resorted to mirror block to avoid vibrations but no matter what I do the focus is off.
QuoteOriginally posted by victormeldrew Quote
Yes. This would be the first thing I would try. You need to do it with every AF lens before using it.
I'm repeating myself, I realise, but just to emphasise, AF fine adjustment won't have any impact on Live View focusing...
09-18-2019, 05:53 AM - 4 Likes   #6
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QuoteOriginally posted by victormeldrew Quote
Yes. This would be the first thing I would try. You need to do it with every AF lens before using it.
I never do that. If I have problem, I find a solution, if I don't have a problem I don't waste time.It's optional.
09-18-2019, 06:17 AM   #7
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Would be handy to know what lens/lenses you are using as well.
09-18-2019, 06:41 AM   #8
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QuoteOriginally posted by dave_roe Quote
Welcome from Rome, It.

Post your examples as suggested above. There are a ton of folks that can offer advice or suggestions.

-dave
And often the problem is not what the OP thinks it is.

What's suspicious in this case is
QuoteOriginally posted by Jnm Quote
It doesn't focus on the wrong area like background for instance, it just doesn't focus perfectly.
With any lens, if you are shooting say from 6 feet to infinity, some part of the image will be in focus, the only thing AF does is determination where the image will be in focus. The above suggests a problem with the actual sensor assembly where in it is very sensitive to movement effectively blurring everything. But I'd have to see images to even make an educated guess.


Last edited by normhead; 09-18-2019 at 06:50 AM.
09-18-2019, 09:25 AM   #9
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QuoteOriginally posted by victormeldrew Quote
Yes. This would be the first thing I would try. You need to do it with every AF lens before using it.
Sorry but I have to say this is bad advice. The OP's problems could be related to a duff lens or a duff camera. Or that he is not aware of how the single focus point he is using works. Could even be old fashioned shutter shock. These are all things that should be investigated and dismissed first. If he now changes the registration distance of potentially all his lenses through the AF/FA menu he could potentially be royally screwed as far as identifying his problem.

I speak as someone who uses 14 different AF/FA adjustments on 14 different lenses on my K1.

---------- Post added 09-18-19 at 05:27 PM ----------

QuoteOriginally posted by Jnm Quote
spot focus
SPOT FOCUS is not a term Pentax uses . Can you please confirm you are not confusing this with SPOT METERING
09-18-2019, 10:38 AM - 1 Like   #10
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Welcome to the Pentax Forums!

The first comment I can make is that the 24Mpx APS-C sensors used in recent model Pentax dSLRs have raised the bar in terms of technique. When the K-3 (my camera) first hit the market, complaints came in almost daily to this site from people unable to attain acceptably sharp photos even using the same lenses and techniques that worked quite well at 16Mpx or lower. The higher pixel density made obvious poor optical performance as well as lapses in technique. The standard answers were to be sure of focus, be attentive to steady hold when off-tripod and quality of support when on-tripod, and to not assign too much weight to the view when pixel peeping at 100%.

That being said, let's lead with one question and then consider what you have shared.

What lens does this happen with and at what focal lengths and shooting distances?

QuoteOriginally posted by Jnm Quote
I think about 20% are tack on, the rest slightly off perfect focus if zoomed.
By zoomed, do you mean 100% (~8X on replay view)? If anything higher than this, one can expect less than the actual sharpness. Even when evaluating at 100%, consistent sharpness when pixel-peeping, shot-to-shot, may be difficult to attain even with the best lenses and best focus systems. 20% less-than-sterling results may not be a cause for alarm. Without example images, it is hard to say.

QuoteOriginally posted by Jnm Quote
I always use afs, back button focus, spot focus, prefer aperture priority usually 8 or 11.
Are you set up for AF-S, shutter priority? By back button, have you changed configuration to allow shutter release with no focus attempt (AF button set to AF2)? If either, there is a higher chance of missed focus unless care is taken to confirm the green hexagon in the viewfinder before releasing the shutter. Back button focus requires quick reflexes for the capture, particularly for moving subjects.

As for aperture used...when "zoomed" to 100%, the normal advantage for DOF at f/8 or f/11 no longer applies. At 100% one is evaluating whether the subject was at the plane of focus. Anything less will be less sharp.

Be aware that even with center spot AF, the area being evaluated may be larger than one thinks and the camera may signal focus for something other than the intended subject or portion of the subject.

QuoteOriginally posted by Jnm Quote
If low light use tripod, Manual mode, live view, 2 sec timer, often high iso as well. I have even resorted to mirror block to avoid vibrations but no matter what I do the focus is off.
In low light, there are too many variables to address here without example images. I'm not sure that live view is a good idea unless you are using electronic shutter. If using AF, I have found the AF assist light to work very well and the PDAF system (optical viewfinder) will offer better performance than the contrast detect system in live view.

Manual focus in live view in dim light is a mixed bag, even if magnified, due to graininess (sensor noise).

QuoteOriginally posted by Jnm Quote
It happens even in bright light situations, although higher percentage are good. It doesn't focus on the wrong area like background for instance, it just doesn't focus perfectly.
A common suggestion on this site is to try AF fine adjustment. Some members here will go as far as stating that fine adjustment should be done for all lenses to assure adequate performance. I fall somewhat shy of that advice and suggest that unless one has firm evidence that the camera's best efforts are consistently behind (back focus) or in front of (front focus) the intended point of focus, there is little to be gained by doing the procedure. Doing a fine tune and doing it right is a lot of work and it is good to rule out other causes before going down that road.

The suggestion above regarding example images and full-resolution (100%) crop to show blur detail would be very helpful. If you need advice on how to do a full-resolution crop, just ask and we will supply detailed instructions.

QuoteOriginally posted by Jnm Quote
Manual focus is not an option because my eyesight is simply not acute enough to identify perfect focus.
Sorry to read this. Your challenge is shared by several other members on this site and you are in good company.


Steve
09-18-2019, 10:48 AM   #11
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QuoteOriginally posted by pschlute Quote
SPOT FOCUS is not a term Pentax uses .
In the KP manual, the center point option is simply called "Spot". The same is true for the K-1, K-70, my K-3, and other recent models. In all fairness, though, the manual for the K-5II uses the term "Center".


Steve

Last edited by stevebrot; 09-18-2019 at 10:54 AM. Reason: Wrong word and factuality
09-18-2019, 11:12 AM   #12
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QuoteOriginally posted by stevebrot Quote
In the KP manual, the center point option is simply called "Spot". The same is true for the K-1, K-70, my K-3, and other recent models. In all fairness, though, the manual for the K-5II uses the term "Center".


Steve
I'll get my coat.

ps nice Rhino
09-18-2019, 01:01 PM - 1 Like   #13
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QuoteOriginally posted by pschlute Quote
I'll get my coat.
I'll meet you in the hall. This kind of subject is difficult and I probably offered as much as I might. Thanks for the compliment on my rhino. It said to say hello to your long-nosed girl next door.


Steve
09-18-2019, 01:40 PM   #14
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Thanks everyone for your comments. I appreciate the advice! I confirm that one point focus is called spot on the kp. I am travelling and do not have my computer with me so I can't submit examples of what I'm complaining about today. I may just be making some ridiculous technical mistake, I am not a pro. Taking up the offer of Stevebrot, yes, it would be helpful to know the proper way to do a full resolution crop.
09-18-2019, 05:11 PM   #15
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Welcome to PF. No need to throw either the camera or yourself off a mountain. We just need to try to break this down.

You say "It doesn't focus on the wrong area like background for instance, it just doesn't focus perfectly." This is what makes me wonder whether we are not talking about AF accuracy at all. If the camera isn't getting focus on the point you want, that will usually be apparent because something in front of or behind that point is in correct focus instead. I think what you are saying is that the images are not sharp enough either in front of or behind the chosen focus point.

The other thing that makes me wonder is that you are having the problem whether using the viewfinder or LiveView for focusing. These two methods use different focusing systems. It's not likely that both are askew.

To take up one of Steve's points, one thing that isn't clear is whether you are using different lenses or just one? If it's just one (or two) it could be the lens(es).

Here's a quick-and-dirty test to see whether your lens might be decentered: How to Check Your Lens for Decentering - Articles and Tips | PentaxForums.com

If you are getting the same issue with multiple lenses, at least we have eliminated one possible cause.

If you can find a way to post some images that would help a lot.

Last edited by Des; 09-18-2019 at 05:23 PM.
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