K-3 AF question (again or not)

**sinus007** · 12-27-2013, 08:27 PM

Hi,
Sorry if it's been asked before - I couldn't find.
In the manual (p. 44) for AUTO selection of focusing area it says "... camera selects the optimum focusing point..." Does anyone know what criteria it uses for the selection? A face, perhaps?
What if there's no face in the picture?
So far, my experiment showed that if a face is inside 5x5 area focus goes to a spot on the face. If the face is outside - the focus goes to some random (seemingly) point. If there's no face at all focus point stay, mostly at the center.

Thank you very much,

Ole · 12-27-2013, 09:40 PM

Face detection only works in connection with live view. When using the view finder and autofocus you raise a good question and I don't have the answer. My experience is that the AF system when left to its own devices tends to focus on what is closest.

I always use only the center point for AF. In this way I get to decide where to focus!

**sinus007** · 12-27-2013, 10:11 PM

Originally posted by Ole

Face detection only works in connection with live view. When using the view finder and autofocus you raise a good question and I don't have the answer. My experience is that the AF system when left to its own devices tends to focus on what is closest.

I always use only the center point for AF. In this way I get to decide where to focus!

Ole,
I did not use Live View. I'm talking view finder.
As for the closest object, good point. In my experiment the face was closest. OTOH, as I mentioned, when it was outside the 5x5 area the focus point went to an object that was farther away from the cam.
In any case, there gotta be some algorithm behind this Auto mode. Unless it made for future models (K-3S, K-3 MkII)

Like you I also use center point, otherwise Mr. Murphy takes total control

Mareket · 12-28-2013, 02:03 AM

I use select point mode number 3 I think, so it focuses on a single point but the subject can be tracked across all 25 centre points after that (just as a heads up that centre point focus is a bad idea quite a lot of the time), and I find that in AF.C it tries to keep the initial point of focus tracked across the frame, so if you focus on a hat, it'll try and keep the hat in focus. Whether this translates over to 27-point automatic selection I'm not sure, though I'd imagine it'd either go for something that's closer or something that's easy t focus on, normally that'd be something closer but as sinus007 found out for whatever reason the K-3 doesn't seem to like that... Seeing as it has the fancy AF sensor you'd think it'd go for something very colourful and bright. Might be worth looking into? It'd be cool if it did go for faces though, especially if it went STRAIGHT FOR THE EYES.

I'd recommend trying the area expansion AF mode thing though, it really is fantastic. You choose the focus point but tracking isn't limited. There's a lot of situations where you just can't focus and recompose.

David&karen · 12-28-2013, 05:58 PM

Only Nikon goes for the eyes as far as I have seen. Makes that brand the darling of wedding photogs.

David

12-27-2013, 08:27 PM	#1
sinus007 Site Supporter Join Date: Jul 2008 Location: Cleveland, OH, USA Photos: Gallery Posts: 292	K-3 AF question (again or not) Hi, Sorry if it's been asked before - I couldn't find. In the manual (p. 44) for AUTO selection of focusing area it says "... camera selects the optimum focusing point..." Does anyone know what criteria it uses for the selection? A face, perhaps? What if there's no face in the picture? So far, my experiment showed that if a face is inside 5x5 area focus goes to a spot on the face. If the face is outside - the focus goes to some random (seemingly) point. If there's no face at all focus point stay, mostly at the center. Thank you very much,

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
K-3 not part of the Camera Raw 8.3 update	boriscleto	Digital Processing, Software, and Printing	6	12-21-2013 09:49 AM
For Sale - Sold: SMC D FA MACRO 1:2.8 100 mm WR -----PRICE DROPPED again- again-again-again	watchman323	Sold Items	12	12-09-2013 11:18 AM
Age old question Filters or not, not!	jamesm007	Pentax SLR Lens Discussion	12	10-23-2013 03:30 AM
Kx user here - should i go to K-5 or K-30 or wait for K-3	ladybug	Pentax K-5 & K-5 II	17	08-18-2012 08:39 AM
Pentax K-x: focus confirmation in AF-S, AF-C, not AF-A	manteiv	Pentax DSLR Discussion	24	12-10-2010 07:25 PM

12-27-2013, 09:40 PM	#2
Ole Administrator Join Date: Sep 2006 Location: Copenhagen, Denmark Photos: Gallery \| Albums Posts: 4,408	Face detection only works in connection with live view. When using the view finder and autofocus you raise a good question and I don't have the answer. My experience is that the AF system when left to its own devices tends to focus on what is closest. I always use only the center point for AF. In this way I get to decide where to focus!

12-27-2013, 10:11 PM	#3
sinus007 Site Supporter Join Date: Jul 2008 Location: Cleveland, OH, USA Photos: Gallery Posts: 292 Original Poster	Originally posted by Ole Face detection only works in connection with live view. When using the view finder and autofocus you raise a good question and I don't have the answer. My experience is that the AF system when left to its own devices tends to focus on what is closest. I always use only the center point for AF. In this way I get to decide where to focus! Ole, I did not use Live View. I'm talking view finder. As for the closest object, good point. In my experiment the face was closest. OTOH, as I mentioned, when it was outside the 5x5 area the focus point went to an object that was farther away from the cam. In any case, there gotta be some algorithm behind this Auto mode. Unless it made for future models (K-3S, K-3 MkII) Like you I also use center point, otherwise Mr. Murphy takes total control

12-28-2013, 02:03 AM	#4
Mareket Veteran Member Join Date: Jun 2011 Location: Chester Photos: Gallery \| Albums Posts: 719	I use select point mode number 3 I think, so it focuses on a single point but the subject can be tracked across all 25 centre points after that (just as a heads up that centre point focus is a bad idea quite a lot of the time), and I find that in AF.C it tries to keep the initial point of focus tracked across the frame, so if you focus on a hat, it'll try and keep the hat in focus. Whether this translates over to 27-point automatic selection I'm not sure, though I'd imagine it'd either go for something that's closer or something that's easy t focus on, normally that'd be something closer but as sinus007 found out for whatever reason the K-3 doesn't seem to like that... Seeing as it has the fancy AF sensor you'd think it'd go for something very colourful and bright. Might be worth looking into? It'd be cool if it did go for faces though, especially if it went STRAIGHT FOR THE EYES. I'd recommend trying the area expansion AF mode thing though, it really is fantastic. You choose the focus point but tracking isn't limited. There's a lot of situations where you just can't focus and recompose.

12-28-2013, 05:58 PM	#5
David&karen Veteran Member Join Date: Jan 2011 Posts: 327	Only Nikon goes for the eyes as far as I have seen. Makes that brand the darling of wedding photogs. David