Yet Another AF Failure From My K-5

Crosshair · 07-21-2012, 06:05 PM

yeah, I guess it was my fault to resort to Auto-AF. I think I aspired a little nikon or canon experience. should be using single AF point all the time and forget about pointing the AF switch to Auto-AF.

cali92rs · 07-21-2012, 06:09 PM

Originally posted by Crosshair

@wizofoz yeah, your suggestion makes sense. the central focusing area extending and overlapping the red guy in the back. so it is proof that the k-5 disregards distance in focusing and looks for the highest contrast on Auto-AF or Single-AF around which point is selected.

Unfortunately, the center focus point is gigantic. You can check this for yourself of course. The work around for this is focus and recompose as mentioned above or manual focus. Both of which have their drawbacks. People want to blame poor AF focus on the user, but frankly, the Pentax AF is lacking. Other systems, you put the focus point over where you want the camera focused and the picture comes out in focus. Things like this just get in the way of taking a picture which is the opposite of what a camera is supposed to do.

rawr · 07-21-2012, 07:01 PM

Originally posted by cali92rs

Other systems, you put the focus point over where you want the camera focused and the picture comes out in focus.

Isn't that what focus and compose using centre spot AF does?
Plus who has time to fiddle with selecting individual AF points out of the 11 you have to choose from?

**Bruce Clark** · 07-21-2012, 07:03 PM

This is a complicated scene with people moving about. I am not the least bit surprised at the AF result. It is possible the subject could have moved after focussing. I use a K-7 myself and this sort of thing is not uncommon.

Solution:-
check the viewfinder,
recompose if necessary.
reshoot if necessary
check results
increase DoF
Use AF-C rather than AF-S
If all else fails go manual.

rawr · 07-21-2012, 07:05 PM

Originally posted by Philoslothical

Auto-11 is a crap shoot at best. Imo, it's basically telling the camera "read my mind" about what to focus on.

Indeed. In the absence of stuff like face-detection to help it realise you want it to focus on people in the frame, the 11 point AF will simply go for contrasty objects with nice defined edges over non-contrasty objects any day of the week.

cali92rs · 07-21-2012, 07:28 PM

Originally posted by rawr

Isn't that what focus and compose using centre spot AF does?
Plus who has time to fiddle with selecting individual AF points out of the 11 you have to choose from?

Say he puts the center point dead center on the guys face, it still could focus on anything within the circular frame shown in the view finder. Including guys in the background, which is probably what happened in the OPs picture. Therefore, using the center point for focus and compose would not have worked in this example unless he put the guys face on the right edge of the circular frame. My point is that people should not have to go through that hassle when much cheaper cameras handle this situation with no sweat at all.

bobpur · 07-21-2012, 07:57 PM

I once built a camera with intelligent AF that could read your mind.... It went home with the blond in the bikini and I never saw it again !
The 11 point is good to catch moving objects like flying birds, better to use the single and pick what you want.

rawr · 07-21-2012, 08:07 PM

I often shoot scenes using centre-spot AF (like small birds sitting in between various layers of foliage) that are much more challenging than the OP's, and have found the centre spot quite workable for that, even on the K-x. K-x pic related:

Lewin's Honeyeater in foliage

Sometimes you have to incrementally shift the AF though (lock on the first object, move slightly until target object gets the focus). But that's to be expected when there may be many equally valid objects for the AF to grab onto within the target zone.

cali92rs · 07-21-2012, 08:23 PM

Thats a wonderful shot, you obviously have talent and know what you are doing. I am not even saying the K-5s AF is terrible. I just wish it was as good as others in its price range.

Ponosby Britt · 07-21-2012, 09:36 PM

I don't know how big the center AF point is but I've never had trouble doing this.

hcc · 07-21-2012, 09:49 PM

Originally posted by JinDesu

Center point helps a lot. Focus and recompose too.

+1 Center point AF will help greatly.

More generally, many experienced Pentaxians would recommand AF Centre point for Pentax dSLR.

hcarvalhoalves · 07-21-2012, 11:02 PM

It's "11 points mode", not "psychic mode". If you know better than the camera that your subject is in the center, just use the center modes (either 5 or spot) instead of fighting your camera.

selar · 07-22-2012, 01:22 AM

Sigma reverse engineers the mount, does not license it from Pentax, for the most part they get it right, but there still are some compatibility issues with the newer bodies. For example, the Sigma 70-200/2,8 HSM II wont lock focus in liveview unless its been re-chipped. So I wouldnt call this a Pentax AF failure, rather a Sigma reverse engineering failure.

Crosshair · 07-22-2012, 02:15 AM

Yeah, thank you all. I think I'm not going to touch the 11-point mode anymore, since Pentax does not have the psychic power of my old D90 which could nail many shots like this without hitch. And I didn't ever see it leave me for a blonde

Like I said somewhere above I thought it was about the closest contrasty thing in the frame, but now I see that Pentax is more about the highest contrast in the scene and to mind the center AF point. I thought the.inabilities of the Sigma too since I had OOF shots like this in the past. My 85* does this too but not as often. And I also decided to use AF-C from now on, since when I don't get the focus I can move the camera slightly and let the k-5 find the true spot.

And I am not fancying canikon things like auto-af area ever again. Only in bird shooting, where it worked quite well.

And IMO I don't see how using the Auto-AF is fighting my camera. If you mean blaming it for blowing focus, no my camera don't fight back so it's not a fight

rawr · 07-22-2012, 02:54 AM

Originally posted by selar

Sigma reverse engineers the mount, does not license it from Pentax, for the most part they get it right, but there still are some compatibility issues...

Probably the same happens with Tamron and Tokina, although both of those have developed lenses together with Pentax in the past, so maybe they know more.

Originally posted by selar

For example, the Sigma 70-200/2,8 HSM II wont lock focus in liveview unless its been re-chipped.

You had me worried, so I just checked mine. It locks focus in LiveView OK, even in low-light and without the AF assist. Once again, my K-5 luck is holding up.

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07-21-2012, 06:05 PM	#16
Crosshair Veteran Member Join Date: Apr 2012 Location: Istanbul Posts: 332 Original Poster	yeah, I guess it was my fault to resort to Auto-AF. I think I aspired a little nikon or canon experience. should be using single AF point all the time and forget about pointing the AF switch to Auto-AF.

07-21-2012, 06:09 PM	#17
cali92rs Veteran Member Join Date: May 2011 Location: Long Beach, CA Posts: 3,354	Originally posted by Crosshair @wizofoz yeah, your suggestion makes sense. the central focusing area extending and overlapping the red guy in the back. so it is proof that the k-5 disregards distance in focusing and looks for the highest contrast on Auto-AF or Single-AF around which point is selected. Unfortunately, the center focus point is gigantic. You can check this for yourself of course. The work around for this is focus and recompose as mentioned above or manual focus. Both of which have their drawbacks. People want to blame poor AF focus on the user, but frankly, the Pentax AF is lacking. Other systems, you put the focus point over where you want the camera focused and the picture comes out in focus. Things like this just get in the way of taking a picture which is the opposite of what a camera is supposed to do.

07-21-2012, 07:01 PM	#18
rawr Veteran Member Join Date: Jun 2009 Posts: 11,913	Originally posted by cali92rs Other systems, you put the focus point over where you want the camera focused and the picture comes out in focus. Isn't that what focus and compose using centre spot AF does? Plus who has time to fiddle with selecting individual AF points out of the 11 you have to choose from?

07-21-2012, 07:03 PM	#19
Bruce Clark Loyal Site Supporter Join Date: Mar 2010 Location: Ocean Grove, Victoria Photos: Gallery \| Albums Posts: 4,458	This is a complicated scene with people moving about. I am not the least bit surprised at the AF result. It is possible the subject could have moved after focussing. I use a K-7 myself and this sort of thing is not uncommon. Solution:- check the viewfinder, recompose if necessary. reshoot if necessary check results increase DoF Use AF-C rather than AF-S If all else fails go manual.

07-21-2012, 07:05 PM	#20
rawr Veteran Member Join Date: Jun 2009 Posts: 11,913	Originally posted by Philoslothical Auto-11 is a crap shoot at best. Imo, it's basically telling the camera "read my mind" about what to focus on. Indeed. In the absence of stuff like face-detection to help it realise you want it to focus on people in the frame, the 11 point AF will simply go for contrasty objects with nice defined edges over non-contrasty objects any day of the week.

07-21-2012, 07:28 PM	#21
cali92rs Veteran Member Join Date: May 2011 Location: Long Beach, CA Posts: 3,354	Originally posted by rawr Isn't that what focus and compose using centre spot AF does? Plus who has time to fiddle with selecting individual AF points out of the 11 you have to choose from? Say he puts the center point dead center on the guys face, it still could focus on anything within the circular frame shown in the view finder. Including guys in the background, which is probably what happened in the OPs picture. Therefore, using the center point for focus and compose would not have worked in this example unless he put the guys face on the right edge of the circular frame. My point is that people should not have to go through that hassle when much cheaper cameras handle this situation with no sweat at all.

07-21-2012, 07:57 PM	#22
bobpur Inactive Account Join Date: Jul 2010 Photos: Gallery Posts: 328	I once built a camera with intelligent AF that could read your mind.... It went home with the blond in the bikini and I never saw it again ! The 11 point is good to catch moving objects like flying birds, better to use the single and pick what you want.

07-21-2012, 08:07 PM	#23
rawr Veteran Member Join Date: Jun 2009 Posts: 11,913	I often shoot scenes using centre-spot AF (like small birds sitting in between various layers of foliage) that are much more challenging than the OP's, and have found the centre spot quite workable for that, even on the K-x. K-x pic related: Lewin's Honeyeater in foliage Sometimes you have to incrementally shift the AF though (lock on the first object, move slightly until target object gets the focus). But that's to be expected when there may be many equally valid objects for the AF to grab onto within the target zone.

07-21-2012, 08:23 PM	#24
cali92rs Veteran Member Join Date: May 2011 Location: Long Beach, CA Posts: 3,354	Thats a wonderful shot, you obviously have talent and know what you are doing. I am not even saying the K-5s AF is terrible. I just wish it was as good as others in its price range.

07-21-2012, 09:36 PM	#25
Ponosby Britt Closed Account Join Date: Jun 2012 Posts: 227	I don't know how big the center AF point is but I've never had trouble doing this.

07-21-2012, 09:49 PM	#26
hcc Pentaxian Join Date: Nov 2009 Location: Brisbane, Australia Photos: Gallery \| Albums Posts: 4,002	Originally posted by JinDesu Center point helps a lot. Focus and recompose too. +1 Center point AF will help greatly. More generally, many experienced Pentaxians would recommand AF Centre point for Pentax dSLR.

07-21-2012, 11:02 PM	#27
hcarvalhoalves Pentaxian Join Date: Aug 2010 Location: São Paulo, Brazil Photos: Gallery Posts: 1,019	It's "11 points mode", not "psychic mode". If you know better than the camera that your subject is in the center, just use the center modes (either 5 or spot) instead of fighting your camera.

07-22-2012, 01:22 AM	#28
selar Veteran Member Join Date: Jul 2007 Location: Sydney, Australia Photos: Gallery \| Albums Posts: 2,042	Sigma reverse engineers the mount, does not license it from Pentax, for the most part they get it right, but there still are some compatibility issues with the newer bodies. For example, the Sigma 70-200/2,8 HSM II wont lock focus in liveview unless its been re-chipped. So I wouldnt call this a Pentax AF failure, rather a Sigma reverse engineering failure.

07-22-2012, 02:15 AM	#29
Crosshair Veteran Member Join Date: Apr 2012 Location: Istanbul Posts: 332 Original Poster	Yeah, thank you all. I think I'm not going to touch the 11-point mode anymore, since Pentax does not have the psychic power of my old D90 which could nail many shots like this without hitch. And I didn't ever see it leave me for a blonde Like I said somewhere above I thought it was about the closest contrasty thing in the frame, but now I see that Pentax is more about the highest contrast in the scene and to mind the center AF point. I thought the.inabilities of the Sigma too since I had OOF shots like this in the past. My 85* does this too but not as often. And I also decided to use AF-C from now on, since when I don't get the focus I can move the camera slightly and let the k-5 find the true spot. And I am not fancying canikon things like auto-af area ever again. Only in bird shooting, where it worked quite well. And IMO I don't see how using the Auto-AF is fighting my camera. If you mean blaming it for blowing focus, no my camera don't fight back so it's not a fight

07-22-2012, 02:54 AM	#30
rawr Veteran Member Join Date: Jun 2009 Posts: 11,913	Originally posted by selar Sigma reverse engineers the mount, does not license it from Pentax, for the most part they get it right, but there still are some compatibility issues... Probably the same happens with Tamron and Tokina, although both of those have developed lenses together with Pentax in the past, so maybe they know more. Originally posted by selar For example, the Sigma 70-200/2,8 HSM II wont lock focus in liveview unless its been re-chipped. You had me worried, so I just checked mine. It locks focus in LiveView OK, even in low-light and without the AF assist. Once again, my K-5 luck is holding up.