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06-13-2009, 08:27 AM   #16
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There's no One right answer, in my opinion.
The centre focus point is probably the most accurate, so it makes sense to use it most often.

However, since the centre of the photograph is not usually where I want to place the focus subject in the final shot, I'd have to focus lock and recompose almost every time. Sometimes its more convenient to select one of the other focus points for multiple shots of roughly the same scene e.g. multiple portrait shots.

Just one little point - if you consider the Rule of Thirds (sorry, going way back to Photography 101 ), the 4 corner focus points in the Pentax correspond to the 4 sweet spots in the scene. Just a bit of convenience, if you choose to use it.

06-13-2009, 08:52 AM   #17
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I use the other points in SEL mode because focus and recompose doesnt always work so well. I would like more points to cover more of the frame since the corner points are not always far enough away from the centre. Thats one thing I was disappointed with when I tried the nikon d3 because it had the same af points as the d300 but because the frame is bigger they were all in the center and none in the corners.
06-13-2009, 08:56 AM   #18
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QuoteOriginally posted by 5teve Quote
i use centre as its what im used to.. but... if more people use multi for a reason.. i may well give it a try... just not sure i trust the camera to choose what i'm focusing on
I use center for the same reason. No way am I going back to letting the camera decide. However, some people like to use the user-select mode for this purpose - you get to pick the focus point, but it doesn't have to be the center. Seems like work to me. But the advantage of more focus points here would be twofold:

- Easier to precisely place the focus point.
- The individual AF sensors would presumably be smaller, thus meaning the camera would be less likely to focus on something outside the little red square used to represent the focus point in the viewfinder. That's a significant issue with current DSLR's - you might have the red square on someone's face, but the background behind them is still within range of the actual AF sensor, which is much larger than the red square, and the camera chooses the background instead.
06-13-2009, 10:48 AM   #19
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I have used multi point auto selection in only one situation, two instances. I was using the DA* 50-135 for indoor soccer and for ice hockey, also indoors, obviously. In both cases, because of my framing techniques that lead the player so as to catch the ball/puck as well as the active players, the camera would often focus on the boards that bound the playing area, when I was using the centre point only. Advertising slogans have really great contrast and attract AF like nobody's business. In this case, I had a somewhat higher success rate with multi point auto selection.

In both cases, I was using autofocus to test the K10 + DA* 50-135 in autofocus mode. I must admit that I was pleasantly surprised, having read, as have you all, a virtually infinite number of posts and reviews that told me not to expect the K10 to focus on anything, getting a quite good number of successful shots.

06-13-2009, 03:34 PM   #20
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QuoteOriginally posted by pschlute Quote
I have a question on AF.

I manually focus a lot, but when I use AF I generally use centre focus point.

But if I use the auto-focus points, how does the camera select focus:

1. by using one of the auto focus points OR

2. by averaging focus based on two or more points ?
I think is always selects the closest (the point closest to the camera where it can find something with contrast) focus point if you have it set to auto. I hardly ever use Auto though, almost always use the centre point only, so could have gotten it wrong.
06-13-2009, 09:58 PM   #21
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QuoteOriginally posted by quarc Quote
I think is always selects the closest (the point closest to the camera where it can find something with contrast) focus point if you have it set to auto. I hardly ever use Auto though, almost always use the centre point only, so could have gotten it wrong.
It seems to prefer the closest point for AF. This works well in the situation I mentioned above, but in other situations, does not work well at all. When I shoot between trees, I want the camera to select the subject behind the trees, for example.
06-13-2009, 10:27 PM   #22
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Thanks guys! All your input was very useful and finally figured out how an autofocus system works and why more points is better with the help of you guys and my dad. Although I don't think I would need more than 11 considering all I do is MF.
06-14-2009, 03:03 AM   #23
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Got a bit over 12000 clicks on my k20d and have center point from day one.

06-14-2009, 09:29 AM   #24
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QuoteOriginally posted by GLXLR Quote
Thanks guys! All your input was very useful and finally figured out how an autofocus system works and why more points is better with the help of you guys and my dad. Although I don't think I would need more than 11 considering all I do is MF.
On a whim, I mounted my DA 12-24 on my K10d, set the camera to MF, the focus point selector dial to Multi, and waved the lens around while looking through the viewfinder with the shutter release half pressed. I discovered that even in MF the camera can use all the focus points. Interesting but useless, I think.
06-14-2009, 06:09 PM   #25
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QuoteOriginally posted by Canada_Rockies Quote
I have used multi point auto selection in only one situation, two instances. I was using the DA* 50-135 for indoor soccer and for ice hockey, also indoors, obviously. In both cases, because of my framing techniques that lead the player so as to catch the ball/puck as well as the active players, the camera would often focus on the boards that bound the playing area, when I was using the centre point only. Advertising slogans have really great contrast and attract AF like nobody's business. In this case, I had a somewhat higher success rate with multi point auto selection.

In both cases, I was using autofocus to test the K10 + DA* 50-135 in autofocus mode. I must admit that I was pleasantly surprised, having read, as have you all, a virtually infinite number of posts and reviews that told me not to expect the K10 to focus on anything, getting a quite good number of successful shots.
I use centre point for rugby as there are always people crossing in front so the AF would go haywire, so I use centre and AF button, so can hold the shutter at half-press the whole time, so reaction time is quicker, SR is already on, and it only focusses when I tell it to.
06-14-2009, 07:43 PM   #26
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QuoteOriginally posted by Zebooka Quote
You just haven't seen *ikon AF point tracking system.
It tracks moving object with AF point through frame while object or your camera is moving. It tracks it by color AE metering system. It's super cool.
Yep, I have a D700 and what amazing focus speed...I hope the K7 is half as fast.
06-15-2009, 02:53 PM   #27
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QuoteOriginally posted by GLXLR Quote
Sorry for sounding so stupid, but I am just a kid that enjoys taking photographs (and not much time too with all honors classes...)
I wasn't that I thought the question was stupid (it's not); I was responding to a tone I thought I read in your original post. Nobody else read it the same way though, and they gave you useful replies, unlike me.

Sorry
06-15-2009, 03:20 PM   #28
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QuoteOriginally posted by GLXLR Quote
What is the big deal about auto-focus points? Isn't 11 points or 9 enough for any type of situation? Could someone explain why anyone would spend extra $$$ on 51 autofocus points when they could just learn how to accurately MF?
Albert gave a very ghood explanation as to why you have so many AF points in some cameras.

Now from the number you seem to be talking about the last nikon AF module and having spend about 18 months with it, I guess I do have some experience, however going over it all is a lot more complex than it sound, as the various AF modes and selectable options makes the caemra reach slightly different.

First of whether you use center only, selectable or "auto select" af point affects how the AF the intial focus acquisition is made.

meaning either it is the center point, one of the 51 points as selected by the user or one of the 51 points selected by the AF module, this affects the 4 main tracking modes on the camera.

1) 9 point tracking (the point of initial focus lock supported by the surrounding AF point)
2) 21 point tracking (as above, but supported by two circles of AF points)
3) 51 point tracking (as above but supported by all the AF points)
4) 51 point 3D tracking ( uses a colour information and some other stuff to determine what you orginially locked on to and use that information to track you original focus point across all of the AF points)

Furthermore you have four different lock on values going from off to long for each of the tracking modes.

Now all this together adds for a very configurable package that takes quite a while to learn how operates and how to tailor to your shooting needs.

IT is far more advanced than what I have seen from my pentax bodies so far, but also far easier to set up "wrong" for what one are about to shoot.
So if you are confident and can operate your camera like second nature, then it is a highly impressive system, but you need to know exactly what you have asked the camera to do or else you may be in for a surprise and a missed shot.

QuoteOriginally posted by 5teve Quote
so as a side question...

what do people use? multi point, selectable, or centre?

i use centre as its what im used to.. but... if more people use multi for a reason.. i may well give it a try... just not sure i trust the camera to choose what i'm focusing on

Thanks

Steve
I use selectable or centre point depending on what I am shooting, center point with AF-C and 3D tracking gives focus and recompose a whole new meaning on the new nikons, quite a useful thing.

But on my K-m it is centre point only on my DS it is selectable and it will be selectable once my K-7 arrives.
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