Many DSLRs have more than one autofocus point. For most shooting styles you only need one AF point - the center one. For situations where you need to selectively focus in a different area while keeping the framing (macro, for instance), more than one AF point would be useful. You could then tell the camera to use the upper right AF point (for example) to find focus instead of using the center one..
Some instances you might want to use all AF points on the camera. One example may be tracking a moving subject at distance, where it is difficult to keep just one AF point on the subject..
For most intents and purposes using more than one AF point can harm your photography, as you can't selectively focus on a particular subject. The camera may choose to focus on an object a few feet in front of your intended subject, and due to DOF issues the intended subject will be out of focus..
Don't base your camera decision solely on number of AF points - there are other important factors such as AF point placement and type of AF point..
IMO there many more significant factors to consider other than AF points, such as AF speed, size/weight/ergonomics, etc.Tim'Be the change you wish to see in the world.' -Mahatma Gandhihttp://www.flickr.com/photos/timskis6/..
I know when I first bought an Elan 7e (and generally wasn't using the e part of that), I went on vacation shortly after getting it, and having not had enough time to really play with it. I left it on the all focus points, and after the vacation found I was really somewhat disappointed in the photos, frequently having the camera focus on the wrong spot. Ever since then I pretty much locked it to using only the center. Of course, I've always kinda wondered since then whether I was missing much by doing that...
It's always easy to use the center-point to lock onto your desired focal point and then sort of slide the camera over to get things composed the way you want them (that's known as the focus-recompose way of doing things)..
However, I think if you have selectable focus-points on the camera, it's good to use them for more precise focusing & exposure-metering. I use my camera to move the point where I want it to be (one of 11), and make sure that my AF-point is linked to the AutoExposure... in otherwords, it makes sure the thing I'm focusing on is generally the thing that it's exposing properly for... but sometimes you might not want that. It gets complicated!.
Long story short - it's good if your camera has more than one selectable point for some situations. Otherwise, I use center a lot...
It's always easy to use the center-point to lock onto your desiredfocal point and then sort of slide the camera over to get thingscomposed the way you want them (that's known as the focus-recomposeway of doing things)..
This works fine for shots with lots of DOF, but when you have shots with shallow DOF (large apertures, for example), moving the camera by "recomposing" even 1cm can significantly change what is in focus and what is not in focus. A perfect example is hand held macro photography, shooting at f/2 or f/2.8 with a long focal length. Recomposing a shot is not even possible in such a situation because the DOF is so razor thin. Add an extension tube to that and you've pretty much committed yourself to using a tripod..
However, I think if you have selectable focus-points on the camera,it's good to use them for more precise focusing & exposure-metering.I use my camera to move the point where I want it to be (one of 11),and make sure that my AF-point is linked to the AutoExposure... inotherwords, it makes sure the thing I'm focusing on is generally thething that it's exposing properly for... but sometimes you might notwant that. It gets complicated!.
I think this is a good point and something I forgot to mention - often cameras use the center point for exposure and a different point for focus. This isn't a problem if you know what you are doing, but I agree that for most situations using AEL/AF linked together is the way to go..
Long story short - it's good if your camera has more than oneselectable point for some situations. Otherwise, I use center a lot..
Tim'Be the change you wish to see in the world.' -Mahatma Gandhihttp://www.flickr.com/photos/timskis6/..
I'm looking into purchasing a DSLR and I was wondering what AF pointsare and what they are used for. I tried the glossary but it onlyexplained about "autofocusing"..
What kind of pictures would having more AF points be useful? Arethere major differences between 3, 9, and 11 AF points?.
Generally a multi AF point system will be better for fast action shots like motor racing as you can set the DSLR to track the car across your viewfinder keeping it in focus. The more focus points the better than cam can do that..
But there are many other uses in particular portrait photography. It is generally good advice to focus on the eyes in such shots. It is difficult to do that with just one focus point. The 11 of the Nikon D80 is near ideal whether taking a shot in portrait or landscape orientation..
I use off centre focus points a lot for theatre photography. I may have the whole stage in view but my main subject may be stage left or stage right..
*Nikon* D Eighty + Fifty - Other equipment in Profile.