Autofocus point-and-shoot cameras produce terrifically sharp pictures when you use them properly. But getting sharp results sometimes requires telling them where to focus.
A common focusing problem occurs when you deliberately place a subject off-center in the viewfinder frame. Say you want to compose the shot of your friends and the mountains this way. You ask your friends to stand to the right so that they block less of the background, giving the mountains center stage in your composition. You point and shoot. But the camera focuses on the mountains because that's where your composition has landed the focus point and your friends end up unsharp in the print. Call it tunnel focus.
Unintentional focusing on the background is, along
with unwanted camera movement, the main cause of unsharp point-and-shoot
pictures. And here's a simple way to avoid it — a photographic one-two punch called locking the focus.
Locking the focus
Lock the focus any time your composition does not place the viewfinder's focus point on the most important part of the scene you're shooting. Locking the focus means that you deliberately make your camera focus on some object in the scene — a person, or something interesting in the foreground — and keep the focus locked at that exact distance until you take the picture. Here's how you lock the focus:
1. Look through the viewfinder and position its focus point on the most important part of the scene — your main subject.
In effect, you center that subject.
2. Press the shutter button halfway down, until the green focus-OK lamp in the viewfinder eyepiece glows steadily.
See the next section, "Making sure your focus is locked," for more on the focus-OK lamp.
3. Holding the shutter button halfway down, reorient the camera so that your desired composition appears in the viewfinder.
4. Press the shutter button all the way down to take the picture.
Back to those friends and the mountains, you lock the
focus by aiming the focus point at your friends (which temporarily puts
them in the center of the viewfinder) and pressing the shutter button
halfway. Then, keeping the shutter button halfway down, you swing the
camera to place your friends off-center (see Figure 1). Now press the
shutter button the rest of the way to take the picture.
Figure 1: Lock the focus to prevent your point-and-shoot from focusing on the background with an off-center subject.
You may need to use this technique with vertical composition, too.
Say you're standing on a rock to shoot a vertical picture in which your
friends are at the bottom of the viewfinder and the mountains in the
background are at the top. To maintain the focus of your friends, first
aim the camera down to place the focus point over one their faces and
press the shutter button halfway. Hold the shutter button halfway down
and swing the camera back up to include the mountains and reestablish
your desired composition. Press the shutter button the rest of the way
to take the picture.
Regardless of your composition — centered or off-center
—always keep your eye on where the focus point lands. Even if your two
friends are smack in the middle of the viewfinder fame, between them is a
little gap and the viewfinder's focus point falls neatly into it. First
"aim" the focus point so that it's on one friend's face, then reorient
the camera to center your friends.
Particularly if you're a landscape fan, you may be wondering what
happens to distant objects when you lock the focus on closer objects.
"If I focus on my friends in front of the mountains, instead of the
mountains," you ask, "then won't the mountains be out of focus?" Not
necessarily.
With most scenes in which you photograph a
relatively close object in front of a distant background, if you focus
on the close object, the background will be reasonably sharp in the
print. But the reverse is not true. Focus on the background — those
mountains — and the close object simply won't be sharp.
Making sure your focus is locked
When you lock your focus, you can't actually see the subject getting sharp in the viewfinder. However, you can verify that your point-and-shoot has autofocused on something by looking at its focus-OK lamp (see Figure 2).
Figure 2: The viewfinder's green focus-OK lamp glows steadily to confirm the focus.
The focus-OK lamp lights up whenever you press the shutter button
halfway. If it glows steadily, it's telling you that the camera has
successfully focused. If the focus-OK lamp blinks, or doesn't light, or
lights briefly but then goes out or starts blinking, it's telling you
that the camera can't focus.More often than not, your camera can't focus because you're too close to the subject. Fix the problem by easing up on the shutter button, stepping back a foot or two, and then pressing the shutter button again.
If you move, the focus doesn't
Locking the focus is vitally important to getting consistently sharp pictures. But remember that when you have that shutter button pressed halfway, the focus doesn't budge. If you ask your subject to move closer or farther away, or you move closer or farther from it to adjust your composition, your subject's no longer in focus. If the distance to the subject changes after you've locked the focus, let up on the shutter button and repeat the focus-locking procedure.
Zoom before you lock the focus. With most point-and-shoot
cameras, locking the focus also prevents you from adjusting the zoom.
If you want to zoom in or out after locking the focus, let up on the
shutter button, adjust the zoom, and then lock the focus again.
0 ความคิดเห็น:
แสดงความคิดเห็น