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12-11-2009, 08:14 AM   #1
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Pentax K-x: focus confirmation in AF-S, AF-C, not AF-A

I was reading that some K-x users were complaining the lack of focus confirmation in the viewfinder.

I searched the internet and found that the focus confirmation is available only for

AF-S
AF-C
not AF-A

what is AF-S, C or A?

12-11-2009, 08:31 AM   #2
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Focus confirmation is available for all modes.

Focus indicator LEDs are not available for any.

AF-S is single, when you focus on one object and hold it (half-)pressed, it will keep the focus where it locked. This includes any movement of you/camera, and the movement of the subject. This is used for recomposing (once you lock focus, you can rotate the camera and the object will stay in focus).

AF-C is continuous, when you focus on an object, holding it (half-)pressed, it will continue to try to keep whatever is in the focus areas in focus, whether you move or the subject moves, or you move the focus area to another subject.

AF-A is auto, and it tries to predict if you are recomposing (stay locked) vs the subject moving (maintain focus)
12-11-2009, 09:11 AM   #3
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so when focus is confirmed, you only hear a bip and that green hexagon icon on the bottom of the viewfinder stays solid?

no red LED overlay? that is disappointing
12-11-2009, 09:24 AM   #4
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Not being offensive at all here, but this argument has been done to death. I personally don't miss them, actually comparatively I find them distracting. I would prefer to focus on my subject and composition. Center point and re-compose works well in most situations, and the AF points can be selected via the rear LCD if you need them (and yes, you may forget which point is selected but you can enable the green button to revert to the center point if you have become lost...)

12-11-2009, 09:25 AM   #5
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Search anywhere and you will find discussions on this.

QuoteOriginally posted by manteiv Quote
so when focus is confirmed, you only hear a bip and that green hexagon icon on the bottom of the viewfinder stays solid?

no red LED overlay? that is disappointing
Disappointing to some, definitely. Usefulness? debatable.
https://www.pentaxforums.com/forums/839932-post9.html

Dissapointed? Simple, find another camera.

Last edited by Eruditass; 12-11-2009 at 09:31 AM.
12-11-2009, 11:58 AM   #6
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well...

I am new. Coming from nikon D40. I am not going to argue whether one can overcome the lack of the focus overlay. I will say that IMHO,

1) It is a weird decision for a camera that targets new SLR users especially that no P&S that I am aware of don't tell you where it is focused. Nor am I aware of any other "entry" level DSLR (the pass 3 or so years anyhow) that does not have the overlay.

2) It dilutes or dare I say -- eliminates the usefulness of 5 pt auto and 11 pt auto. Since it is hard to tell (especially in low light) with the lower quality view finder in this "entry" level camera where camera has chosen the focus. The camera does default at 5 pt auto coming out of the factory. For a newb like my self, at times, i like to set to "auto" because I find the scene challenging and don't want to miss the shot, I may still miss it due to missed focus. Yes, I can choose center pt. Then, why even bother with all the pts?

3) <rant> the whole focus recompose is to me... old school folks that don't want to adapt new technology. Yes, it is true that motion photos has been taken and taken well, long before the multipoint focus invention (and done with manual focus to boot). But, why fight technology? It is like saying the automatic transmission in car is poo poo because manual stick works just as well. Of course you can. No one is denying that. But, there is a reason that vast majority of cars are auto. Besides, why note 11 pt "cross" focus points as a pro vs N*/C* bodies' 1 - 3 cross pts when you only use the center one (which takes away the pro of pentax) </rant>

I am of the opinion that my points are valid (with exception of perhaps the <rant>). Again, I am not arguing whether one can live with them or not... nor am I going to tell you to chose another camera. That's for other threads and individuals to decide.
12-11-2009, 12:01 PM   #7
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1) Agreed, it has and will continue to turn off new users.
2) Agreed on limiting the usefulness of 5-pt and 11-pt in static scenes. I do use 5-point and 11-point for birding and small rc planes where the object can pass between many of the points and there is not much else for it to focus on. If they are going in and out of branches and whatnot, 5-point and 11-point are useless anyway even with indicators because it will just tell me I focused on the wrong thing, but I will have missed the shot anyway. You really have to use a camera (with LED indicators) in these situations in order to make an assessment. In this case I use select-point.

If you find the scene challenging and don't want to choose a focus point/miss the shot, what are focus point indicators going to help you with?
3) Agreed

(missed point) The whole point I have made is that select-AF point, IMO the most useful, works just as good if not better than the competition (cross-type).

Last edited by Eruditass; 12-11-2009 at 12:07 PM.
12-11-2009, 12:38 PM   #8
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Well, you mean that every p&s digicompact has focus confirmation and overlay in the optical viewfinder? I can say that they do not! First of all, most p&s digicompacts doesn't even have an optical viewfinder! And those that do, does not show focus overlay in the optical viewfinder.

P&S digicompacts uses the back LCD to show point of focus, and with many you can also use the arrow keys to select which focus point you want. The K-x works this way - The AF points are displayed on the back LCD and here you can use the 4 way controller to select which one of the focus points you wish to use for the shot! It is quick and easy, and works the same way as many p&s digicompacts do. So for one coming from p&s digicompacts and wants to buy their first DSLR - this is standard procedure of changing AF points.

So yes the 11 points does come handy.
And yes, the camera do shows which one of them you choose - on the big back LCD!

12-11-2009, 01:24 PM   #9
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@RMabo:

Of course I meant with the rear LCD as most P&S of late don't have a view finder at all.

I understand your point in selection of the focus points. but, since you are also composing via the LCD, you do see the points selected. I do believe (un)able to see this is what causes this whole discussion to begin with no?

It would be lovely that when picking auto, the back LCD shows the points chosen as oppose to remain just "auto 5 or 11"

FYI Not all P&S allows picking. the new P&S such as the canon SD78IS does not allow picking of points other than center as well as many others I am sure.

But, Honestly, the P&S small censor + large DOF really hides many focus mistakes casual users make.

@Eruditass:

that is precisely the point. at least you can see that the camera picked the wrong points and thus adjust either where you are pointing at to get the points right or forced to learn the use of manual select (i.e., learn the camera on the fly).

As for cross-type, I was under the impression that k-x/k7 comes with 11 cross-type pts vs other brands of 1 -> 3 cross type pts. I believe that's why pentax in theory, has a more accurate focus?

OT and geeky... I love RC stuff too.
12-11-2009, 01:40 PM   #10
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QuoteOriginally posted by slow2focus Quote
@Eruditass:

that is precisely the point. at least you can see that the camera picked the wrong points and thus adjust either where you are pointing at to get the points right or forced to learn the use of manual select (i.e., learn the camera on the fly).
Perhaps I didn't explain myself but if you can see the camera picked the wrong focus point, then there must be a right focus point, which you could've told the camera to use instead of keep trying and hoping it will select the right one? If you change where you are pointing the camera, isn't this the same as focus - recomposing? Or are you accepting the new framing?

And of course this is only acceptable on non-moving scenes, with moving scenes, you will miss the shot with x-point AF if it doesn't focus right the first time, which it would with select-point.
QuoteQuote:

As for cross-type, I was under the impression that k-x/k7 comes with 11 cross-type pts vs other brands of 1 -> 3 cross type pts. I believe that's why pentax in theory, has a more accurate focus?

OT and geeky... I love RC stuff too.
As I understand it, non-cross type is not sensitive to phase differences in the Y axis, only the X axis (or vice versa). This will mean slower detection of phase differences when the line is not horizontal and completely ignorant of vertical lines (or vise versa).
12-12-2009, 03:54 PM   #11
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QuoteOriginally posted by slow2focus Quote
It is like saying the automatic transmission in car is poo poo because manual stick works just as well. Of course you can. No one is denying that. But, there is a reason that vast majority of cars are auto.</rant>
In the UK, almost everyone drives manual - and yes, automatic is poo-poo'd
12-12-2009, 04:18 PM   #12
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I'm still confused. Autofocus often doesn't work for me and I end up focusing manually to get the right shot. I find center point autofocus to be the most useful for this camera *k-m because it's the only one that I know for sure where it is.
12-24-2009, 01:55 PM   #13
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QuoteOriginally posted by Eruditass Quote
Focus confirmation is available for all modes.

Focus indicator LEDs are not available for any.

<skipped>


AF-A is auto, and it tries to predict if you are recomposing (stay locked) vs the subject moving (maintain focus)
I ask about AF-A in my month long experience thread and I don't get the inputs from anyone. I wonder if users with K-x knows how AF-A predicts which mode to go with AF-C or AF-S? Does it have any smart in the prediction or is it just a switch to different scene mode?

I don't see the documentation on AF-A especially on how the camera chooses the mode between AF-C and AF-S.

Thanks,
Hin
01-02-2010, 01:16 AM   #14
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Help me decide to purchase a K-x

I bought a Spotmatic more than forty years ago when Honeywell marketed the Pentax brand. Currently, I have a Spotmatic and a Canon EOS film camera which has selectable focus zones displayed in the viewfinder. I am about to purchase a DSLR. I am drawn to the K-x but may get a Canon 450D.

Please, don't repeat all the tired arguments above. Rather, if you have a K-m or a K-x, tell me from your experience how to approach the situations I will describe. Center focus and recompose is not an option.

You are at the family Christmas party and many people are seated and others are milling around in various locations around a large room, wondering in and out of any shot you might want. Kids are running around.

(1) You are looking to freeze the scene at various instants when opportunities are presented. You see Granny sitting in the middle of the room and Grandpa is three feet closer. You want Granny to be focused in the left of the frame, Grandpa in the center, and the spinster aunt, who is four feet further back on the right. Granny is making a momentary gesture that will only last a second and you want it on the image.

You are shooting in room light and the image seen in the pentamirror is not bright and well defined. How do you know if the camera is focused on Granny or Grandpa or the Aunt, or the flowers just in front of Granny?

I would use my EOS, not my Spotmatic, here. If the camera did not select Granny I could quickly select the proper focus point.

(2) In other situations you might see a shot developing and pre-select your subjects. Then, at the proper moment, take the shot. It would not be practical to center-focus and then hold that for a lengthy period while the shot was developing and while the subject(s) were moving about. The subjects would move out of focus. I would select a focus spot over the main subject and could get the shot even if he moved closer or farther away, and with some cameras could even track him. If he moved out of the focus point I would know that (because I could see all the focus points) before I took the shot and could easily re-aquire him.

I hope someone can sort this out for me because I would like to purchase the K-x.
01-02-2010, 01:49 AM   #15
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actually, I never check any red dot or green hexagon, I just listen to the beep, when it's focused, it's got a beep, so that i can focus on the people instead of my camera.
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