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Exposure Control Modes

Depending on the type of digital camera you bought, it usually have one or more exposure control modes. Besides the obligatory Auto mode, many digital cameras now also provide Scene Modes. Cameras geared for the serious amateur photographers also feature Shutter-Priority, Aperture-Priority, and full Manual modes.

This tutorial explains what they are, and when and how to use them for best results.

Auto

Auto mode, as its name implies, delegates all decision making to the camera. Your digital camera will select the shutter speed, aperture, ISO, white balance, and other settings it believes will give the best result in the majority of situations.

Most Point-and-Shoot (P&S) cameras have only Auto Mode since their intended audience doesn't -- or necessarily wants to -- know how to select shutter speed, aperture, and other settings. This includes most buyers of digital cameras. P&S digital cameras also typically sharpen the picture for you in camera and set colours to saturated. P&S photographers desire pictures that "look good" right out of the camera -- without having to do any post-processing in a photo editing software.

Auto mode works well in most picture-taking situations. In a few situations -- that may or may not occur frequently, depending on the kind of pictures you like to take -- the camera in Auto mode is unable to reproduce what your eyes see. Some of these situations include a sunset with deep colours; fireworks; bright snow or beach scenes; night scenes; action scenes. The camera is "fooled" in these situations and capture less than satisfying results.

Take the example of a sunset. Because we are looking at the sun, our eyes automatically squint and our iris closes down. The result is that we see the sunset colours as rich, saturated and deep. The camera, on the other hand, has no idea you are taking a sunset. All it knows is that when it measures the light level in the frame bounded by the LCD monitor (or viewfinder), it's pretty dark. So, it averages it all out and allows more light in than your eyes do, resulting in a picture that is too bright with washed out colours.

If your sunsets don't come out with the deep colours your eyes see, now you know why. The solution: underexpose the shot by one or more stop. Don't understand what this means? Despair not, for your camera probably provides you with a "Sunset" scene mode that basically does the same thing automatically for you.

The other scene modes adjust the exposure automatically (even firing the onboard flash, if necessary), depending on the mode you select. But do ensure you use the appropriate scene mode for the situation, or you will not get the desired results. We will look at some scene modes below.

By the way, do not take a sunset picture if you cannot comfortably look at it -- or you will damage your eyes and may also damage the camera's image sensor.

Programmed Auto

Program Auto mode is very similar to Auto mode, but allows you to fix some of the settings so the camera does not change them on you. For example, you can fix ISO to 100, and let the camera decide on the other settings. In Auto mode, the camera would have changed the ISO if the necessity arose.

This gives you more exposure flexibility if you understand how exposure works. Typically, the camera will then also allow you to fix other settings, such as image sharpness, contrast and saturation; the type of metering; white balance; exposure compensation; etc.

If you are learning about photography, you want a digital camera that has Programmed Auto. If a picture does not come out as your eyes see it, you can then adjust one of the settings to compensate for a picture that comes out too bright or too dark, for example. In Auto mode, you're basically stuck. In Program Auto mode, you can make the camera behave the way you want it to and override its exposure decisions.

Center Focus
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, most of the time, we use a handy technique called Pre-Focus. By pre-focusing, I mean that we swivel the camera slightly so that the center rectangle is on the subject, depress the shutter release half-way to lock focus, then swivel the camera back for our desired composition, and depress the shutter release fully to take the picture.

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
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, 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. And repeat that procedure for every picture where you want to move the AF frame. No wonder we don't use this focus mode as often, preferring instead to use pre-focusing.

Even then, 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 correctly 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.

An Example
Here is an example of how Area Focus helped 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.


Fujifilm FinePix S5000
Programmed Auto, Multi-Pattern metering, Macro ON
19mm, 1/180 sec., F3.2, ISO 200

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.


Fujifilm FinePix S5000
Programmed Auto, Multi-Pattern metering, Macro ON
19mm, 1/170 sec., F3.2, ISO 200

So, why not try Area Focus, 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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