Most of the newer digital cameras include three focusing modes: Center Focus, Area Focus and Multi Focus. If you are sometimes getting out of focus pictures even when your camera indicates successful focus lock, you need to understand the difference between these focusing modes.
Center Focus will focus on the center of the frame.
Multi Focus automatically selects between a number of AF frames and focuses on the most contrasty subject closest to the center of the frame. For example, if your main subject (i.e. the subject you want to be in focus) stands beside some other object (behind or in front of your main subject) of greater contrast, the camera will focus on the latter object and your main subject will be out of focus. So, if you use Multi Focus as your default focus mode, this may explain why many of your shots are out of focus.
Area Focus deserves some explanation. I believe it is a focus mode that few uses, but there are certain situations where Area Focus is perfectly suited for and can help you capture a sharply focused shot where the other focus modes fail.
If you look in the LCD of your digital camera, there will be a rectangle at the center of the screen, commonly called the AF frame. This AF frame depicts the zone where the camera will focus on.
If your subject is smack in the middle of the screen, well and good. But, what if your subject is not in the center of the screen?
Well, we use a handy technique called Pre-Focusing. Pre-focusing simply means that you center your subject on the center AF frame, depress the shutter release half-way (which will cause the camera to lock focus), then swivel the camera back to your desired composition, and finally depress the shutter release fully to take the picture. In other words, we “pre-focus,” compose, then we take the picture.
In the example above, the butterfly is not centered. If we take a picture using center focus, the butterfly will be out of focus. We move the camera so as to center the butterfly in our screen, half-press the shutter release button to lock focus on the butterfly, then recompose and depress the shutter fully to take a picture that is now in sharp focus.
Pre-focusing is used extensively in action photography when you know that you want to take the picture at a certain fixed spot. In this case, you can pre-focus on that spot by a half-press of the shutter release, then follow the action and depress the shutter fully when your subject reaches the fixed spot. Examples of a fixed spot can be a basketball hoop, a finish line, a spot right in front of you, etc.
Area Focus extends Center Focus by allowing the AF frame to be moved anywhere on the screen. So now, if your subject is to the left of center, instead of moving the camera left, pre-focusing and then moving the camera back, all you do is move the AF frame left instead while keeping the camera still!
On some cameras, Area AF is implemented very well and you can move the AF frame easily without taking your eye off the LCD or viewfinder. On others, you need to go into the menu, set Area Focus mode and position the AF frame where you want it to be using the four-way controller.
Most of the time, pre-focusing works as well as Area AF. But there is at least one photo situation where Area Focus is perfect for: macro photography. When taking a close-up you may want to compose your picture so that the subject is at one corner of the frame. Since precise focus is paramount in close-up shots (depth of field is very shallow), pre-focusing can be difficult to achieve since when you recompose you may end up moving the camera a little closer or further to your subject. The result is an out-of-focus picture (your main subject will be out of focus though other parts of the picture may be in focus).
This is where area focus comes in and saves the day.
By moving the AF frame on your subject to the corner of the frame so that it covers your subject, you can maintain your composition without having to move your camera, lock your tripod, set your self-timer, and take the shot — for a spot on, razor sharp image.
Here is an example of how Area Focus helps me achieve sharp focus in a macro shot. The AF frame in the center of the frame encompasses both the fir needles and the leaves. Where will the camera focus on: the fir needles (which is what I want) or the leaves in the background? In the first picture, using Center Focus, the fir needles do not come out as sharp as I want; instead the leaves get the focus.When I try to pre-focus, moving the camera back to my composition is enough to lose precise focus.
I could switch to Manual Focus but I don’t trust my eyes (even with a central enlarged image). I could switch to Multi Focus and let the camera decide on the most contrasty area. But why leave this to chance? I decide to use Area Focus instead. In the second picture, I move the AF frame to the bottom left, completely covering the fir needles. Result: fir needles in focus, leaves in background nicely blurred.
So, why not try Area Focus next time if your camera allows it? You may find that, besides macro photography, there are other instances when it is the appropriate focus mode to use.
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