Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
04-11-2016, 08:48 AM   #1
New Member




Join Date: Apr 2016
Posts: 5
Focus Issues on New K3

I had the K-x before and upgraded keeping my K-x as backup. I also have the Pentax 40mm limited prime lens which I shoot with almost exclusively. I was noticing that a lot of my photos on the K3 were not quite in focus with the 40 mm. Additionally, I have the Pentax 50mm 1.8 as well and noticed that pictures seemed soft. So I figured the 50 lens was bad and that maybe I wasn’t doing something right with the 40. But just the other day I shot with the 40 back on my K-x and the focus was spot on perfect, and the K3 could get a good shot. Even though there was plenty of light at ISO 200. The camera is focusing perfectly fine and quick but when editing, it is off. When I try to focus on the eyes, it is doing it a little behind the subject. I have messed with the micro AF settings and hopefully this helps (+8) which seems to be a really high adjustment. It just seems weird to me that both the prime lenses are not shooting good on the K3 at normal settings, and my K-x is still out performing the K3 with the focus by far. Doing Spot Focus and Tripod on both, standing about 5 to 6 feet from subject. Thanks for any help!

04-11-2016, 09:04 AM   #2
Senior Member




Join Date: Jul 2014
Posts: 105
Aside from the micro-focus adjustments, I'd make sure the SR is turned off if you are using a tripod. Are you using a remote shutter release, or pushing the camera's shutter button?
04-11-2016, 09:04 AM   #3
Site Supporter
jatrax's Avatar

Join Date: May 2010
Location: Oregon
Photos: Gallery | Albums
Posts: 10,770
QuoteOriginally posted by chezrock Quote
it is doing it a little behind the subject.
Back focusing. On the k-x you have only one adjustment so it is basically all or nothing. On the k-3 you can set specific adjustments for 20 lenses. Oddly I had to use adjustments on many lenses on my k-5 but on my k-3 and k-3II things have been spot on, just lucky I guess.

Anyway, research auto-focus fine tune. Please do not just 'mess' with those settings. Without precise calibration you are just guessing. Use a tripod and a good focusing target. Or a Lens Align device if you have access to one. The camera must be precisely aligned with the plane of the focus target in both vertical and horizontal directions. Take several shots at each setting and average the results.

That is just a simple summary, do a search for auto-focus fine tune and you will find lots of good information.
QuoteOriginally posted by chezrock Quote
hopefully this helps (+8) which seems to be a really high
Anything less than 10 is fine. You should test all of your lenses. If on the off chance they are all off by a large similar amount I would consider sending the camera back as defective if you still can or sending it in to Pentax for calibration. But I would not do that without precise testing on a good number of lenses.
04-11-2016, 09:16 AM   #4
New Member




Join Date: Apr 2016
Posts: 5
Original Poster
Thanks for the response. I am manually pushing the shutter button.

I have made the fine adjustment already without being too scientific about it. I tried a ruler on a slant at F2.8 and aimed for one value and tried to see how far off it was that way. I also did it with a person subject and shot 4 shots at each adjustment to see which looked the best. I didn't get any more technical than this. There is a shop near me that does calibration for $39 so I might just go that route if it doesn't fix the issue. I guess my question would be it seems to be only integer increase/decrease of the micro adjustments. So can I really screw it up by messing with them or is it causing other issues by my doing this? Thanks!

04-11-2016, 09:44 AM   #5
Pentaxian




Join Date: Sep 2008
Location: Phoenix, AZ
Posts: 1,434
QuoteOriginally posted by chezrock Quote
Thanks for the response. I am manually pushing the shutter button.

I have made the fine adjustment already without being too scientific about it. I tried a ruler on a slant at F2.8 and aimed for one value and tried to see how far off it was that way. I also did it with a person subject and shot 4 shots at each adjustment to see which looked the best. I didn't get any more technical than this. There is a shop near me that does calibration for $39 so I might just go that route if it doesn't fix the issue. I guess my question would be it seems to be only integer increase/decrease of the micro adjustments. So can I really screw it up by messing with them or is it causing other issues by my doing this? Thanks!
you aren't going to mess up anything, it only affects the sensor position in the body to compensate for the misaligned focal plane.

with that said, your k-x may be off, but with the smaller MP sensor, it's much more forgiving than the k3. there are hundreds of threads on PF about how the slightest flaws in technique or lens alignment suddenly become glaring errors on the k3. In the long run you will be a better, more knowledgeable photographer after you have learned how to solve all this minor issues.

but you must learn the concepts behind the errors and how to solve them, including the manual shutter press on a tripod. some of your out of focus shots could really be motion blur that the 24mp is now revealing.

read up on the MUP settings and invest in a remote or cable shutter release. camera shake on a manual shutter press can last up to 3 seconds. on the k3 this could really affect your images.
04-11-2016, 10:03 AM   #6
Site Supporter
jatrax's Avatar

Join Date: May 2010
Location: Oregon
Photos: Gallery | Albums
Posts: 10,770
QuoteOriginally posted by chezrock Quote
So can I really screw it up by messing with them or is it causing other issues by my doing this?
No it will not harm anything. But we often see folks that take a snapshot (handheld) adjust the AF fine tune, take another snapshot and so on. They are basically using a random selection process and so my initial comment about precision. You can with a little effort dial the AF in quite reliably, but you can also just get lucky.

As nomadkng states the k-x was a very forgiving camera, great for starting out. But a lot of people who bought the k-3 (including myself) were rudely informed that the k-3 is a serious camera but is not very forgiving of poor technique or calibration. I had gotten very sloppy and had to go back to basics before I got the k-3 to perform as it should. Simply the act of pushing the shutter button can be enough (if you are not braced and holding properly) to move the camera several centimeters, enough to cause a soft image on the k-3.
QuoteOriginally posted by nomadkng Quote
In the long run you will be a better, more knowledgeable photographer after you have learned how to solve all this minor issues.
Well said. Buying a new camera has never by itself made my pictures any better, but each new camera k-x>k-5>k-3 has forced me to up my skills and that has resulted in better images.
04-11-2016, 11:28 AM - 1 Like   #7
Site Supporter
stevebrot's Avatar

Join Date: Mar 2007
Location: Vancouver (USA)
Photos: Gallery | Albums
Posts: 27,424
Congratulations on your new K-3 and welcome to the world of picky technique. Soon after the K-3 debuted, this site had frequent new threads regarding disappointing (soft) results from the new camera. The causes may be summarized as follows:
  • Any lapse in focus or deficiency in lens quality is much more obvious when pixel peeping a 24Mpx capture than at half that resolution (your K-x)
  • Even a small amount of camera motion can be deadly
  • Missed focus is much more obvious
The first point is simply a matter of perception. To screen for this, simply downsample the soft image to 12.4 Mpx and evaluate the sharpness of that version as if it were made using your K-x. The second is a matter of technique. I have learned to be much more aware of camera hold, bracing, and breathing in a manner similar to what I use with my film cameras. When using a tripod, be sure to turn SR off. I suggest using the 2s delay. Remote shutter release (IR or wired) may also be a good idea for some subjects. On the matter of tripods, it has been my observation that most people try to get away with support that is inadequate for their kit.

Now back to your focus issues. As I mentioned above, your complaint is not unique. I suggest the following before devoting (wasting) a lot of effort doing a valid AF fine adjust:
  • Using a high contrast FLAT test target with camera on tripod about 20x - 40x the focal length distant, attempt manual focus using magnified live view. The purpose is to see whether your lens is capable of sharp results to your standards with the K-3. If not, you can stop here as far as that lens is concerned.
  • The second step is to evaluate the PDAF system using the same set up and limiting yourself to the center focus point in AF-S mode. Reset the fine adjust to zero. Do 20 focus attempts, 10 racking from far-to-near and 10 from near-to-far. Of the 20, how many have obvious missed focus? Is that number unacceptably high?
If the answer to the last question is yes, the next task is to determine if the missed focus is due to poor precision (not something you can fix) or poor calibration (something you may be able to partially address with a fine AF adjust). I won't go into detail about how to do the fine adjust except to say that the matter of precision is important. Even if properly calibrated, it is unlikely that the PDAF system will lock to the same plane of focus every time in a test of 20 exposures as we did above. Ideally those results will be equally distributed on both sides of the desired plane of focus. In that case, there is no need or benefit in doing any fine adjustment. If more results focus behind the subject, you have backfocus. If the opposite, you have front focus. There are several ways to evaluate front/back focus with the most common being: a) some sort of scale/target device that allows easy visualization or b) use of magnified live view as the gold standard and observing the direction the PDAF moves the focus ring to attain its own notion of correctness. Either way, it is important to base the direction, amount of correction, and confirmation on multiple focus attempts. If you use a slant scale device be sure that the target is flat and parallel to the camera focal plane. Your intent is to provide an unambiguous subject.

Oh, and one other thing...it is fairly common for zooms and internal focus lenses to require different adjustment at different distances and/or focal lengths. That kind of adjustment may be done by the owner of certain Sigma lenses that support the USB Dock device, but for most lenses, a shop with the appropriate Pentax calibration instruments is needed.


Steve

Last edited by stevebrot; 04-11-2016 at 11:35 AM.
04-11-2016, 11:37 AM   #8
Pentaxian




Join Date: Feb 2015
Photos: Albums
Posts: 3,522
QuoteOriginally posted by chezrock Quote
Focus Issues on New K3 I had the K-x before and upgraded keeping my K-x as backup. I also have the Pentax 40mm limited prime lens which I shoot with almost exclusively. I was noticing that a lot of my photos on the K3 were not quite in focus with the 40 mm. Additionally, I have the Pentax 50mm 1.8 as well and noticed that pictures seemed soft. So I figured the 50 lens was bad and that maybe I wasn’t doing something right with the 40. But just the other day I shot with the 40 back on my K-x and the focus was spot on perfect, and the K3 could get a good shot. Even though there was plenty of light at ISO 200. The camera is focusing perfectly fine and quick but when editing, it is off. When I try to focus on the eyes, it is doing it a little behind the subject. I have messed with the micro AF settings and hopefully this helps (+8) which seems to be a really high adjustment. It just seems weird to me that both the prime lenses are not shooting good on the K3 at normal settings, and my K-x is still out performing the K3 with the focus by far. Doing Spot Focus and Tripod on both, standing about 5 to 6 feet from subject. Thanks for any help!
Yes, that's normal, I experienced the same issue. I had a K200D and the 40ltd delivered sharp images. Then I acquired a K-3, and got some not so sharp images from the K-3. I sent the 40 Ltd for testing buy the official Pentax repair lab in Europe. Explanation: the Kx is 12Mpixels, the K-3 is 24Mpixel without antialias filter. Therefore when zooming in at 100%, any imperfection from the AF accuracy or the lens sharpness will become visible on the K-3. The DA40 limited as a very short focus throw and is screw drive, mechanical step tolerance insufficient for the AF precision requirement of the 24Mpixel OAA less sensor. Sorry to be so straightforward but... take a look at the 40 limited review on PF, and you see that the reviewer had some issues with the 40 Limited (https://www.pentaxforums.com/reviews/da-35mm-40mm-limited-xs-shootout/image-q...sharpness.html). What happens with the 40 Ltd is that the AF quick shift mechanism gets a bit loose over time, and then the small mechanical play of the AF barrel make the AF relatively inaccurate for a K-3. Check if the AF barrel of the DA40 Ltd is slightly loose (only 0.5mm is sufficient to loose perfect focus on the K-3), if so, sent it for a quick shift repair or keep the lens as it is if the blur is not dramatic.


Last edited by biz-engineer; 04-11-2016 at 11:50 AM.
04-11-2016, 11:53 AM   #9
Site Supporter
stevebrot's Avatar

Join Date: Mar 2007
Location: Vancouver (USA)
Photos: Gallery | Albums
Posts: 27,424
QuoteOriginally posted by biz-engineer Quote
Yes, that's normal, I experienced the same issue. I had a K200D and the 40ltd delivered sharp images. Then I acquired a K-3, and got some not so sharp images from the K-3. I sent the 40 Ltd for testing buy the official Pentax repair lab in Europe. Explanation: the Kx is 12Mpixels, the K-3 is 24Mpixel without antialias filter. Therefore when zooming in at 100%, any imperfection from the AF accuracy or the lens sharpness will become visible on the K-3. The DA40 limited as a very short focus throw and is screw drive, mechanical step tolerance insufficient for the AF precision requirement of the 24Mpixel OAA less sensor. Sorry to be so straightforward but... take a look at the 40 HD limited review on PF, and you see that the reviewer had some issues with the 40 HD Limited on the K-3. What happens with the 40 Ltd is that the AF quick shift mechanism gets loose over time, and then the small mechanical play of the AF barrel make the AF relatively inaccurate for a K-3. Check if the AF barrel of the DA40 Ltd is slightly loose (only 0.5mm is sufficient to loose perfect focus on the K-3), if so, sent it for a quick shift repair or keep the lens as it is if the blur is not dramatic.
Thanks for this comment! Your hand-on experience with the DA 40 on the K-3 is extremely valuable.


Steve
04-11-2016, 12:10 PM   #10
Site Supporter
jpzk's Avatar

Join Date: Jan 2009
Location: Québec
Photos: Gallery | Albums
Posts: 7,255
QuoteOriginally posted by jatrax Quote
No it will not harm anything. But we often see folks that take a snapshot (handheld) adjust the AF fine tune, take another snapshot and so on. They are basically using a random selection process and so my initial comment about precision. You can with a little effort dial the AF in quite reliably, but you can also just get lucky.

As nomadkng states the k-x was a very forgiving camera, great for starting out. But a lot of people who bought the k-3 (including myself) were rudely informed that the k-3 is a serious camera but is not very forgiving of poor technique or calibration. I had gotten very sloppy and had to go back to basics before I got the k-3 to perform as it should. Simply the act of pushing the shutter button can be enough (if you are not braced and holding properly) to move the camera several centimeters, enough to cause a soft image on the k-3.

Well said. Buying a new camera has never by itself made my pictures any better, but each new camera k-x>k-5>k-3 has forced me to up my skills and that has resulted in better images.
Well said, for me too !
I admit that this K3 is one heck of a step up from my good ol' trustworthy K5 and if I am not careful while focusing/aiming/composing the results can be rather disappointing.
OTOH, when you nail the focus, using careful technique, it is superbly sharp.
I have taken near 400 pictures so far (recent purchase) with the K3 and only for the past few times have I been telling myself that things are getting better.
At some point, I was even tempted to return it !

Lots of good advice here!

Cheers!
04-11-2016, 04:39 PM   #11
New Member




Join Date: Apr 2016
Posts: 5
Original Poster
Thanks for the great input! I understand there are more things to deal with when it comes to the K3 vs. the Kx, but I can't imagine a setting is doing what is going on. I shoot RAW on both cameras, and it is always the same focal length. No movement from myself or the subject. I haven't posted anything yet for pictures but would like to, to give some context and would be interested to see if you still think the same thing. Today I went out and shot some with the K3 first, and then switch the lens (40mm) to my Kx. The first 2 are from the K3, the second from the Kx. For these photos I am shooting Aperture P. All were trying to single focus on one eye or the other. Thanks again!
Attached Images
View Picture EXIF
PENTAX K-3  Photo 
View Picture EXIF
PENTAX K-3  Photo 
View Picture EXIF
PENTAX K-x  Photo 
View Picture EXIF
PENTAX K-x  Photo 
04-11-2016, 06:49 PM   #12
Pentaxian




Join Date: Feb 2015
Photos: Albums
Posts: 3,522
Photos #1 the pink clothe is in focus, not the eye. photo #2, back focused, photo #3 and #4 the clothes are in focus. I don't see any of both camera doing better. Depth of field is approx. 0.75ft, when framing the subject the way it is here and 40mm f4. You should be able to correct the backfocus with AF microadjust, and that's what you did:
QuoteOriginally posted by chezrock Quote
I have messed with the micro AF settings and hopefully this helps (+8) which seems to be a really high adjustment.
As long as +10 isn't reached, that's what AF fine adjust is for. Have you tried live view AF of the K-3, and focusing on the eye or face detection mode, compare the results?
Attached Images
 

Last edited by biz-engineer; 04-11-2016 at 07:13 PM.
04-11-2016, 08:05 PM   #13
New Member




Join Date: Apr 2016
Posts: 5
Original Poster
Quick questions when using the calculator. If on the crop sensor, if I am using the 40mm, do I need to input 60mm as the focal length? Even at where I am, .75ft is quite large isn't it? I would have to move a lot to have that be the issue. But this would seem to really help with when I would have multiple people in the frame and how far apart their faces are off plane. From previous posts, there was talk about shooting with on hand and not the tripod, but the K-3 has the built in shake reduction that I thought would correct for 1 stop, wouldn't this help with any little movement I might have when depressing the button? Sorry for all the questions, just trying to get my head around this problem.
04-11-2016, 10:36 PM   #14
Pentaxian




Join Date: Feb 2015
Photos: Albums
Posts: 3,522
QuoteOriginally posted by chezrock Quote
Quick questions when using the calculator. If on the crop sensor, if I am using the 40mm, do I need to input 60mm as the focal length?
There is no need to enter the 25 equivalent focal length.

QuoteOriginally posted by chezrock Quote
Even at where I am, .75ft is quite large isn't it?
You know it, it is just fine for your subject, but does not allow much focus error from the camera or from the camera user.

QuoteOriginally posted by chezrock Quote
From previous posts, there was talk about shooting with on hand and not the tripod, but the K-3 has the built in shake reduction that I thought would correct for 1 stop, wouldn't this help with any little movement I might have when depressing the button?
As you know; that wouldn't help, K-3 SR does not correct for a move in the Z direction.

QuoteOriginally posted by chezrock Quote
Sorry for all the questions, just trying to get my head around this problem.
Well, that's understandable, you want the focus where it should be. If you can't correct it with AF fine adjust, then return the lens, send it for adjustment, try another lens.
04-11-2016, 11:13 PM   #15
Site Supporter
beachgardener's Avatar

Join Date: Sep 2013
Location: Australia
Photos: Gallery
Posts: 2,053
My K-3 needed a fine AF adjust of 8 for all, either - or + can't recall, but any lens on the K-3 is spot on now, quite a nice camera.

Also I choose which focus point mostly, instead of centre point and focus then compose, that can have an effect too, put it out slight at large apertures.

Last edited by beachgardener; 04-11-2016 at 11:16 PM. Reason: add info.
Reply

Bookmarks
  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
autofocus, dslr, focus, focus issues, k-3, k-x, k3, lens, pentax, pentax k-3, settings, shot, spot, subject
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
k3 focus issues ckschempp Troubleshooting and Beginner Help 24 03-23-2015 01:24 PM
Focus issues k3 or lens? 5teve Pentax K-3 19 02-27-2015 02:19 AM
K3 cold weather focus issues jmurray Troubleshooting and Beginner Help 11 02-11-2014 06:15 AM
New K3 - Focus/Soft Image Issues Red Solo Cup Pentax K-3 14 01-12-2014 03:09 PM
About focus issues on new lenses cooldude14es Pentax SLR Lens Discussion 4 07-28-2008 09:31 AM



All times are GMT -7. The time now is 02:41 AM. | See also: NikonForums.com, CanonForums.com part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top