[GLXLR]

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?

[Quension]

You're asking why people would like to use AF instead of MF?

...Seriously?

[Kguru]

Can someone please explain how 51 autofocus points work?

Does that mean it would preferentially shoot at f/16 for max dof to ensure all 51 points are in focus, or does it give us a choice to pick out of 51 points together with a super-quick method to indicate which one (like eyeball control)?

Thanks.

[kittykat46]

Can someone please explain how 51 autofocus points work?

Does that mean it would preferentially shoot at f/16 for max dof to ensure all 51 points are in focus, or does it give us a choice to pick out of 51 points together with a super-quick method to indicate which one (like eyeball control)?

Thanks.

There are two ways the 51-point autofocus can be used.

a) Manually select, using the control buttons, which of the 51 points to use, the same way you can manually select which 11-point focus on the Pentax. Personally I don't think this method provides any real practical advantage with 51 points.

b) Set it to auto-select. The camera makes a "best-guess" focus out of 9, 21 or all 51 (user selectable). This works the same way as Pentax's Auto Focus Point select.

It does have practical use in fast changing action scenes where you just do not have time or predictability to focus-lock then and recompose. Even toddlers can provide a focusing challenge in such a situation.

You point the camera in the general direction to take the shot, then let the camera optimise the focus on the overall scene. It usually focuses on the nearest objects.

Having 21 or 51 points to optimise the focus does do a better job compared to 9.

[GLXLR]

You're asking why people would like to use AF instead of MF?

...Seriously?

I mean if you would spend so much money on a 1Ds mark iii just for the focus points... but of course there is the D300.

I have used my GX-10 for quite a bit and I have used MF for 95% of my shots, but even with the 5% of shots I do use AF for, I feel like the 11points are more than sufficient for my needs. I mean if you had 51 auto focus points, and then you say that you are taking a picture of a moving person (considering he covers 50% of the frame) AGG i am confuzzled.... Isn't the area of focus a vertical plane? So why would you need 51 autofocus points to confirm focus on the same plane? O_O Pleaseeee explainnnnnn

Sorry for sounding so stupid, but I am just a kid that enjoys taking photographs (and not much time too with all honors classes...)

[pschlute]

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 ?

[Rondec]

I think the whole point of multiple auto focus points is to assist with tracking. 90 percent of the time, I use center point and recompose, but certainly if you are doing wildlife photography, sports photography, it helps to have more focus points.

As to the whole manual versus auto focus debate, I have to say I fall squarely in the auto focus camp. As someone mentioned already, tracking a toddler with manual focus is nearly impossible. Static scenes or macro shots are a different story.

[Zebooka]

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.

[ftpaddict]

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.

It's called a Nikon. And their bodies are very good at tracking. Played around with a D3. Very impressive.

Will the K-7's AF compare to the Nikon's? Find out by reading RH's blog.

[Kguru]

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 ?

Drawing from the posts here I think the answer is by using one of the AF points, which one depends on its "best guess".

[GLXLR]

So if you have more points and you track a moving subject, is it less likely to hunt?

[Canada_Rockies]

Yes. There is less distance between two points on a subject that is moving across the focus area. It is much easier for the software to "hand off" the focus to the next point because they are virtually touching one another. There is less subject "blackout" for the auto focus system. It also takes some more horsepower in the hardware, of course.

[5teve]

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

[ftpaddict]

I use centre as well.

[jdg]

I use the center as well.