Action Autofocus - Just Not Getting It

jcleary47 · 08-19-2018, 04:56 PM

My woes with Autofocus on my K3-II continue to baffle me. I've read numerous threads with suggestions and best practices but I seem to still just be having issues.

My primary issue is this - I'm photographing my children, so naturally they move around, but there are times when they aren't really moving all that much or that fast, and I know that I've focused on their face, but when I look at my photos in my editor after, it is clear as day that the auto-focus locked onto something else, often part of their clothing near their head or something next to their head in the background.

Most recently today outside, I had nice lighting so I could use a really fast shutter speed and everything so really felt like I could play with auto-focus to figure it out. I tried AF-S, AF-C, single point focus, full point focus. I always seem to have an issue where a ton of my shots are just locking onto something else even when I know I've got it centered right on their face.

Is it me? Is it an issue with my camera? I'm fairly new to shooting things that move, so maybe it's something I'm doing. I've always been more of a landscape and still-life kind of guy. There's been lots of threads out there about this but two and two is obviously not going together for me, unless there's a possibility of an issue with my camera. I just don't know.

Here's an example attached to my post: AF-C, single point autofocus. I have little doubt I had this shot pointed center of his face as I was tracking him and he wasn't all that mobile. Looks to me like it locked onto his sleeve.

Attached Images

View Picture EXIF

**Pentax Syntax** · 08-19-2018, 05:37 PM - **1 Like**

From the Exif info it looks like you are shooting the FA limited 77 at 3.5 200 ISO. The depth of focus will be small at that focal length and aperture. Have you calibrated autofocus with that lens? That could explain why spot focus would not catch the face.

jcleary47 · 08-19-2018, 06:19 PM

Hrm, no I've never calibrated the auto-focus with any of my lenses. I'll look into that.

stevebrot · 08-19-2018, 07:08 PM - **5 Likes**

Here are the basic rules. Some are the same as with manual focus and some are not. A few are intentionally tongue-in-cheek, but are still important.:

There is no magic mode. What's more, what magic there is will readily disperse whenever the camera is pointed towards active children and/or dogs
If you allow the camera to choose the point of focus, chances are pretty good that the camera's choice will be different than yours. While letting the camera choose often works quite well, don't expect the results to be perfect. The camera will choose the first point where it deems focus is attainable within the set zone.
If you tell the camera the intended point of focus (spot or select), the camera will make its best effort to acquire focus at that point, but focus is not acquired until it signals such (green hexagon and beep). The red dot only indicates the active focus point.
Accurate fine focus requires that the intended point of focus be unambiguous and have detail. A curved surface is ambiguous as is a region of low contrast.
Once acquired, whether the camera attempts to retain focus depends on mode. This never happens in AF-S mode. AF-C mode is used for continuous focus.
AF-A is only useful if you don't care to know that is happening
AF-S and AF-C are equally fast
Unless set to "focus priority", the shutter will release regardless of whether focus has been attained. This is true for both AF-S and AF-C.
There is only one plane of focus and like all planes, it is infinitely thin. As a result, viewing at full resolution (pixel peeping) will often as not indicate that the plane of focus is not within your image.
Do not expect the camera to create depth of field when the lens says there is none. The range of acceptable focus may be quite reasonable at f/5.6 for a particular lens and subject distance, but be completely unworkable at f/2.
Focus attained at a particular point in time is not likely to be accurate for more that a few milliseconds when shooting children or dogs in motion
Camera motion is often mistaken for missed focus
Manual focus film SLRs usually have some form of focus aide such as a split-image rangefinder or microprism grid. Both are very good at consistently detecting an out of focus subject. Modern PDAF systems are not quite as consistent at that task. The CDAF system (live view) is quite a bit better, but relatively slow.
The AF point is both larger and smaller diameter than one might think. (Ponder that for awhile.)
The AF speed of a particular lens/camera is never adequate unless it is another brand in the hands of someone else
Regardless of claims made by enthusiastic users, "nailing" focus seldom happens hand-held or with a moving subject
While the camera's AF is potentially much faster, if the subject would be difficult to focus on using manual technique (even if stationary), chances are the camera will have a hard time with it as well

My K-3 has essentially the same AF behavior as your K-3II and I am quite pleased with its AF system. It is quite a bit better than that in the K10D that I had before. I do a lot of manual focus work but also use AF where critical focus control is not strongly desired. Usually, I use AF-S (focus priority), spot (center point) with classic focus-recompose technique. If photographing a cluster of kids, I might move to AF-C (shutter priority), 9-point zone select. A short burst of shutter might also be in order as also might f/5.6 or f/8. I usually don't photograph clusters of kids, so that last statement may work great or may not. Being a traditionalist with decades of manual focus experience, I may fall back to manual focus technique even for moving subjects. It works very well for bicycle and motor racing. I don't photograph dogs running around the yard.

P.S. On your example photo, focus is on the boy's right shoulder. If you were shooting AF-S (focus priority) spot, there is a chance that the camera is "front-focused" with this lens. Determining if this is the case and applying fine tuning might be worth doing, but is something I generally don't recommend unless one is sure that the fine adjustment is appropriate.

Steve

(...stopped just short of suggesting a D500, but even that camera may not be up to the active kid challenge...)

Last edited by stevebrot; 08-19-2018 at 07:33 PM.

**david94903** · 08-19-2018, 09:46 PM - **3 Likes**

Originally posted by Pentax Syntax

From the Exif info it looks like you are shooting the FA limited 77 at 3.5 200 ISO. The depth of focus will be small at that focal length and aperture. Have you calibrated autofocus with that lens?

With the FA77 on a crop sensor body, at f3.5, you depth of field would only be about 8" if you were at a distance of 10' from your subject. If you were closer, it'd be less. At f8, your DOF would be about 20" at 10'. I learned the hard way early on shooting photos of my kids, I needed all the DOF I could get, because kids don't ever remain still as soon as the camera comes into play; so f8 or f11 has been my preferred kid capture stop. Additionally, performing lens calibration through AF Fine Adjustment may also help. I found that most of my DA lenses didn't need a lot of adjustment, but some of my FA lenses needed quite a bit more help with the front focus/back focus fine tuning. Well worth doing with every lens.

jawsy · 08-20-2018, 03:31 AM - **1 Like**

Originally posted by stevebrot

I do a lot of manual focus work but also use AF where critical focus control is not strongly desired.

For the reasons outlined in previous post's I use manual focus when it really needs to count also. As an aside, I was recently asked to shoot a dance comp using someone else's DLSR; a Canon in similar thin DoF conditions. I was curious as to how it would go in AF and after ten minutes and all the reasons outlined in previous posts had to revert to manual focusing.

That said, my FA77 needed +8 on the AF calibration scale so check that out.. Your posted image reminds me of the pre-calibration AF on my own copy.

jcleary47 · 08-20-2018, 04:15 AM - **1 Like**

Awesome, thank you all for the advice. I really appreciate it! I'll double check the calibration on all of my lenses, and also I think a little more practice shooting the little ones will help as well!

CarlJF · 08-20-2018, 07:38 AM - **3 Likes**

I have a K3 (similar autofocus than your K3-II) and, as a father of three, I shoot a lot of kids! A lot a good suggestions above, particularly to check if your lens is correctly calibrated.

That said, taking live, non posed, pictures of kids require a lot of practice to get constantly good results. And even then, you have to expect a lot of trash. Particularly in the case of relatively thin depth of field shots as the one shown above.

At 77mm, f3.5, you only have a few inches of leeway and even slight movement in or out from you or the child would results in a "misfocused" shot. It's okay to try thin DOF kids shot, but do not expect 100% perfectly focused shots on the nearest eye. Just take a lot of shots, keep the ones that are good and delete the others (which can mean most of them). On the other hand, if you want to go the safe way and be sure to have an acceptable picture (thus putting more emphasis of "taking the moment" rather than "technical perfection"), you can close down to 5.6 or even f8, which will gave more leeway for any movements or focus imprecision. Sure, the background blur will not be as good but the subject will be sharp, which is more important than a nice looking background. And will get near 100% sharp pictures.

In the end, it's a question of compromise between having a lot of "only good" shots with few missed ones and having a lot of missed shots with a few potentially oustanding ones. Only you can decide which compromise is acceptable for a given situation. Sometimes you may decide that it's better to be sure to have at least an acceptable shot and stop down to f8, and other times decide to you can take your chance with some wide open shots even it means that none might be good...

**Larrymc** · 08-20-2018, 11:36 AM - **1 Like**

Originally posted by jcleary47

Awesome, thank you all for the advice. I really appreciate it! I'll double check the calibration on all of my lenses, and also I think a little more practice shooting the little ones will help as well!

Looks like a front focus issue. If you've never calibrated your K-3 with the 77 or any lens for that matter, read the section on AF Fine Adjustment in the manual carefully before you proceed, you won't break anything and whatever you changed can be reversed if need be. For a quick and dirty adjustment try setting the Fine Tune (Apply One) to a +5 and take some photos just to check . There are several charts available on the internet but the best way to fine tune is with a precision device like the Lens Align or the Spyder Lens Cal. Do some reading about the subject first so you are familiar with the results you might get.

CarlJF · 08-20-2018, 12:00 PM - **1 Like**

Originally posted by Larrymc

Looks like a front focus issue. If you've never calibrated your K-3 with the 77 or any lens for that matter, read the section on AF Fine Adjustment in the manual carefully before you proceed, you won't break anything and whatever you changed can be reversed if need be. For a quick and dirty adjustment try setting the Fine Tune (Apply One) to a +5 and take some photos just to check . There are several charts available on the internet but the best way to fine tune is with a precision device like the Lens Align or the Spyder Lens Cal. Do some reading about the subject first so you are familiar with the results you might get.

For front focus, a -5 adjustment would be more advisable... But yes, a quick check like this is a good idea. If the adjustement seems to improve things, it would confirm a front focus issue.

**Larrymc** · 08-20-2018, 12:41 PM - **1 Like**

Originally posted by CarlJF

For front focus, a -5 adjustment would be more advisable... But yes, a quick check like this is a good idea. If the adjustement seems to improve things, it would confirm a front focus issue.

Yep you're precisely right a -5.......I must have had my dumb beanie on when I typed that!

Thanks

stevebrot · 08-20-2018, 12:54 PM - **1 Like**

Originally posted by Larrymc

Looks like a front focus issue.

Either that or focus was not attained when the shutter was released (i.e. no green hexagon).

Steve

**monochrome** · 08-20-2018, 01:27 PM - **1 Like**

Originally posted by jcleary47

Awesome, thank you all for the advice. I really appreciate it! I'll double check the calibration on all of my lenses, and also I think a little more practice shooting the little ones will help as well!

That’s a fine idea, but I think you’d be better-served shooting at ISO 640 or 800 and closing your aperture two or three stops. You should get the same exosure value, likely won’t have any excess noise, but you’ll increase the Zone of Focus dramatically - perhaps by 2x or 3x - as noted above. Try this first before the 45 minutes it will take to focus-tune each lens.

Also, try to keep your shutter speed above 1/77 (1/FL) by bumping ISO rather than opening aperture, where possible. IIRC from before I sold my K-3, noise is not a big issue below 1600 in decent light and K-3ll is better at noise than K-3.

**Wingincamera** · 08-20-2018, 01:35 PM - **1 Like**

There are various ways to check & adjust the fine focus adjustment of your lens. I stumbled upon the DotTune method and find it really easy.
dot-tune method - Bing video

aaacb · 08-20-2018, 08:08 PM

You could also check in custom settings that you have focus priority set in af-c if you're shooting with continuous drive. I set everything to focus priority (and not shutter/rate priority) because otherwise it seems to decide "good enough" is fairly out of focus.

08-19-2018, 07:08 PM - 5 Likes	#4
stevebrot Otis Memorial Pentaxian Join Date: Mar 2007 Location: Vancouver (USA) Photos: Gallery \| Albums Posts: 42,007	Here are the basic rules. Some are the same as with manual focus and some are not. A few are intentionally tongue-in-cheek, but are still important.: There is no magic mode. What's more, what magic there is will readily disperse whenever the camera is pointed towards active children and/or dogs If you allow the camera to choose the point of focus, chances are pretty good that the camera's choice will be different than yours. While letting the camera choose often works quite well, don't expect the results to be perfect. The camera will choose the first point where it deems focus is attainable within the set zone. If you tell the camera the intended point of focus (spot or select), the camera will make its best effort to acquire focus at that point, but focus is not acquired until it signals such (green hexagon and beep). The red dot only indicates the active focus point. Accurate fine focus requires that the intended point of focus be unambiguous and have detail. A curved surface is ambiguous as is a region of low contrast. Once acquired, whether the camera attempts to retain focus depends on mode. This never happens in AF-S mode. AF-C mode is used for continuous focus. AF-A is only useful if you don't care to know that is happening AF-S and AF-C are equally fast Unless set to "focus priority", the shutter will release regardless of whether focus has been attained. This is true for both AF-S and AF-C. There is only one plane of focus and like all planes, it is infinitely thin. As a result, viewing at full resolution (pixel peeping) will often as not indicate that the plane of focus is not within your image. Do not expect the camera to create depth of field when the lens says there is none. The range of acceptable focus may be quite reasonable at f/5.6 for a particular lens and subject distance, but be completely unworkable at f/2. Focus attained at a particular point in time is not likely to be accurate for more that a few milliseconds when shooting children or dogs in motion Camera motion is often mistaken for missed focus Manual focus film SLRs usually have some form of focus aide such as a split-image rangefinder or microprism grid. Both are very good at consistently detecting an out of focus subject. Modern PDAF systems are not quite as consistent at that task. The CDAF system (live view) is quite a bit better, but relatively slow. The AF point is both larger and smaller diameter than one might think. (Ponder that for awhile.) The AF speed of a particular lens/camera is never adequate unless it is another brand in the hands of someone else Regardless of claims made by enthusiastic users, "nailing" focus seldom happens hand-held or with a moving subject While the camera's AF is potentially much faster, if the subject would be difficult to focus on using manual technique (even if stationary), chances are the camera will have a hard time with it as well My K-3 has essentially the same AF behavior as your K-3II and I am quite pleased with its AF system. It is quite a bit better than that in the K10D that I had before. I do a lot of manual focus work but also use AF where critical focus control is not strongly desired. Usually, I use AF-S (focus priority), spot (center point) with classic focus-recompose technique. If photographing a cluster of kids, I might move to AF-C (shutter priority), 9-point zone select. A short burst of shutter might also be in order as also might f/5.6 or f/8. I usually don't photograph clusters of kids, so that last statement may work great or may not. Being a traditionalist with decades of manual focus experience, I may fall back to manual focus technique even for moving subjects. It works very well for bicycle and motor racing. I don't photograph dogs running around the yard. P.S. On your example photo, focus is on the boy's right shoulder. If you were shooting AF-S (focus priority) spot, there is a chance that the camera is "front-focused" with this lens. Determining if this is the case and applying fine tuning might be worth doing, but is something I generally don't recommend unless one is sure that the fine adjustment is appropriate. Steve (...stopped just short of suggesting a D500, but even that camera may not be up to the active kid challenge...) Last edited by stevebrot; 08-19-2018 at 07:33 PM.

08-20-2018, 12:41 PM - 1 Like	#11
Larrymc Site Supporter Join Date: Jun 2014 Location: Mississippi, USA Posts: 5,252	Originally posted by CarlJF For front focus, a -5 adjustment would be more advisable... But yes, a quick check like this is a good idea. If the adjustement seems to improve things, it would confirm a front focus issue. Yep you're precisely right a -5.......I must have had my dumb beanie on when I typed that! Thanks Last edited by Larrymc; 08-20-2018 at 12:47 PM.

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08-19-2018, 05:37 PM - 1 Like	#2
Pentax Syntax Loyal Site Supporter Join Date: Feb 2010 Location: Maryland Posts: 595	From the Exif info it looks like you are shooting the FA limited 77 at 3.5 200 ISO. The depth of focus will be small at that focal length and aperture. Have you calibrated autofocus with that lens? That could explain why spot focus would not catch the face.

08-19-2018, 06:19 PM	#3
jcleary47 Forum Member Join Date: Dec 2007 Location: Westbrook, ME Posts: 74 Original Poster	Hrm, no I've never calibrated the auto-focus with any of my lenses. I'll look into that.

08-19-2018, 09:46 PM - 3 Likes	#5
david94903 Loyal Site Supporter Join Date: Nov 2010 Location: San Rafael, CA Photos: Gallery \| Albums Posts: 806	Originally posted by Pentax Syntax From the Exif info it looks like you are shooting the FA limited 77 at 3.5 200 ISO. The depth of focus will be small at that focal length and aperture. Have you calibrated autofocus with that lens? With the FA77 on a crop sensor body, at f3.5, you depth of field would only be about 8" if you were at a distance of 10' from your subject. If you were closer, it'd be less. At f8, your DOF would be about 20" at 10'. I learned the hard way early on shooting photos of my kids, I needed all the DOF I could get, because kids don't ever remain still as soon as the camera comes into play; so f8 or f11 has been my preferred kid capture stop. Additionally, performing lens calibration through AF Fine Adjustment may also help. I found that most of my DA lenses didn't need a lot of adjustment, but some of my FA lenses needed quite a bit more help with the front focus/back focus fine tuning. Well worth doing with every lens.

08-20-2018, 03:31 AM - 1 Like	#6
jawsy Veteran Member Join Date: Mar 2009 Location: Australia Photos: Gallery \| Albums Posts: 422	Originally posted by stevebrot I do a lot of manual focus work but also use AF where critical focus control is not strongly desired. For the reasons outlined in previous post's I use manual focus when it really needs to count also. As an aside, I was recently asked to shoot a dance comp using someone else's DLSR; a Canon in similar thin DoF conditions. I was curious as to how it would go in AF and after ten minutes and all the reasons outlined in previous posts had to revert to manual focusing. That said, my FA77 needed +8 on the AF calibration scale so check that out.. Your posted image reminds me of the pre-calibration AF on my own copy.

08-20-2018, 04:15 AM - 1 Like	#7
jcleary47 Forum Member Join Date: Dec 2007 Location: Westbrook, ME Posts: 74 Original Poster	Awesome, thank you all for the advice. I really appreciate it! I'll double check the calibration on all of my lenses, and also I think a little more practice shooting the little ones will help as well!

08-20-2018, 07:38 AM - 3 Likes	#8
CarlJF Veteran Member Join Date: Sep 2014 Location: Quebec City Posts: 1,185	I have a K3 (similar autofocus than your K3-II) and, as a father of three, I shoot a lot of kids! A lot a good suggestions above, particularly to check if your lens is correctly calibrated. That said, taking live, non posed, pictures of kids require a lot of practice to get constantly good results. And even then, you have to expect a lot of trash. Particularly in the case of relatively thin depth of field shots as the one shown above. At 77mm, f3.5, you only have a few inches of leeway and even slight movement in or out from you or the child would results in a "misfocused" shot. It's okay to try thin DOF kids shot, but do not expect 100% perfectly focused shots on the nearest eye. Just take a lot of shots, keep the ones that are good and delete the others (which can mean most of them). On the other hand, if you want to go the safe way and be sure to have an acceptable picture (thus putting more emphasis of "taking the moment" rather than "technical perfection"), you can close down to 5.6 or even f8, which will gave more leeway for any movements or focus imprecision. Sure, the background blur will not be as good but the subject will be sharp, which is more important than a nice looking background. And will get near 100% sharp pictures. In the end, it's a question of compromise between having a lot of "only good" shots with few missed ones and having a lot of missed shots with a few potentially oustanding ones. Only you can decide which compromise is acceptable for a given situation. Sometimes you may decide that it's better to be sure to have at least an acceptable shot and stop down to f8, and other times decide to you can take your chance with some wide open shots even it means that none might be good...

08-20-2018, 11:36 AM - 1 Like	#9
Larrymc Site Supporter Join Date: Jun 2014 Location: Mississippi, USA Posts: 5,252	Originally posted by jcleary47 Awesome, thank you all for the advice. I really appreciate it! I'll double check the calibration on all of my lenses, and also I think a little more practice shooting the little ones will help as well! Looks like a front focus issue. If you've never calibrated your K-3 with the 77 or any lens for that matter, read the section on AF Fine Adjustment in the manual carefully before you proceed, you won't break anything and whatever you changed can be reversed if need be. For a quick and dirty adjustment try setting the Fine Tune (Apply One) to a +5 and take some photos just to check . There are several charts available on the internet but the best way to fine tune is with a precision device like the Lens Align or the Spyder Lens Cal. Do some reading about the subject first so you are familiar with the results you might get.

08-20-2018, 12:00 PM - 1 Like	#10
CarlJF Veteran Member Join Date: Sep 2014 Location: Quebec City Posts: 1,185	Originally posted by Larrymc Looks like a front focus issue. If you've never calibrated your K-3 with the 77 or any lens for that matter, read the section on AF Fine Adjustment in the manual carefully before you proceed, you won't break anything and whatever you changed can be reversed if need be. For a quick and dirty adjustment try setting the Fine Tune (Apply One) to a +5 and take some photos just to check . There are several charts available on the internet but the best way to fine tune is with a precision device like the Lens Align or the Spyder Lens Cal. Do some reading about the subject first so you are familiar with the results you might get. For front focus, a -5 adjustment would be more advisable... But yes, a quick check like this is a good idea. If the adjustement seems to improve things, it would confirm a front focus issue.

08-20-2018, 12:54 PM - 1 Like	#12
stevebrot Otis Memorial Pentaxian Join Date: Mar 2007 Location: Vancouver (USA) Photos: Gallery \| Albums Posts: 42,007	Originally posted by Larrymc Looks like a front focus issue. Either that or focus was not attained when the shutter was released (i.e. no green hexagon). Steve

08-20-2018, 01:27 PM - 1 Like	#13
monochrome Loyal Site Supporter Join Date: Mar 2008 Location: Working From Home Photos: Gallery \| Albums Posts: 26,276	Originally posted by jcleary47 Awesome, thank you all for the advice. I really appreciate it! I'll double check the calibration on all of my lenses, and also I think a little more practice shooting the little ones will help as well! That’s a fine idea, but I think you’d be better-served shooting at ISO 640 or 800 and closing your aperture two or three stops. You should get the same exosure value, likely won’t have any excess noise, but you’ll increase the Zone of Focus dramatically - perhaps by 2x or 3x - as noted above. Try this first before the 45 minutes it will take to focus-tune each lens. Also, try to keep your shutter speed above 1/77 (1/FL) by bumping ISO rather than opening aperture, where possible. IIRC from before I sold my K-3, noise is not a big issue below 1600 in decent light and K-3ll is better at noise than K-3.

08-20-2018, 01:35 PM - 1 Like	#14
Wingincamera Loyal Site Supporter Join Date: Oct 2012 Location: Pine Haven, Wyoming Photos: Gallery \| Albums Posts: 1,182	There are various ways to check & adjust the fine focus adjustment of your lens. I stumbled upon the DotTune method and find it really easy. dot-tune method - Bing video

08-20-2018, 08:08 PM	#15
aaacb Pentaxian Join Date: May 2016 Photos: Gallery Posts: 3,726	You could also check in custom settings that you have focus priority set in af-c if you're shooting with continuous drive. I set everything to focus priority (and not shutter/rate priority) because otherwise it seems to decide "good enough" is fairly out of focus.