F-Stop/ISO/White Balance

Setting the Right F-Stop for Your Digital Photo

Your digital camera’s aperture settings (f-stops) can make a world of difference, so choosing the right f-stop can be an important part of creating a perfect finished picture. You need different f-stops for different photographic situations:

Use an almost-wide-open f-stop to boost sharpness.

Most cameras and lenses are their sharpest when they’re closed down only one or two f-stops from wide open. This setting can also help you stop camera or subject motion, creating a clear action shot, like in this figure.

Adjust your depth of field by moving f-stops.

Changing your f-stops can stretch your depth of field usefully or trim it for creative effect. Stopping down or opening up an f-stop or two can produce dramatically different results, as shown in this figure.

Avoid too-small f-stops.

Using the smallest possible f-stop can cause defraction, and you lose any sharpness you think you gain in depth of field. In addition, small f-stops can accentuate the appearance of any tiny dust motes on your sensor (see this figure). These imperfections, at larger apertures, are fuzzy and virtually invisible.

F-Stop

The "F" in f-stop stands for "focal length." The focal length divided by the pupil diameter, or the amount of light entering the lens determines the f-stop number. It is often expressed as something like "f/16" or "f/3." The number denotes the width of the opening in the aperture, which is an opening behind the camera lens. The aperture works rather like the pupil of the eye, and swirls narrower or wider, depending on the desired amount of light. Odd as it sounds, the larger the f-stop number, the smaller the opening in the aperture. F/16 is a smaller opening than f/3.

Depth of field is how much background is visible behind the main object in the photo. For instance, if a photographer wants to show a single flower in a field, he will use a wide f-stop and a faster shutter speed. This will blur the background, bringing the flower into sharp focus. If, however, the photographer is taking a shot of friends in front of a mountain vista, she will use a narrower f-stop and a slower shutter speed. This enables the photographer to capture her friends in the foreground, as well as the mountains behind them, with all in sharp focus

 

ISO settings/Light sensitivity

Many digital cameras offer a choice of ISO settings, which indicate the light sensitivity of the camera’s imaging sensor. The higher the ISO number, the more quickly the camera reacts to light. A high ISO setting increases light sensitivity, but it can also add noise to the picture.

For some shooting scenarios, you may be forced to use a higher ISO. For example, if you’re trying to capture a moving subject, you may need to raise the ISO so that you can use the fast shutter speed necessary to freeze the action.

Experiment with ISO settings if your camera offers them. But, for best picture quality, keep the ISO at its lowest or next-to-lowest setting.

White Balance

Digital cameras use a process known as white balancing to tell the camera what combination of red, green, and blue light it should perceive as pure white, given the current lighting conditions. With that white-identifying information as a baseline, the camera can then accurately reproduce the other colors in the scene.

Although white-balance controls are designed to improve color accuracy, some digital photographers use them to mimic the effects produced by traditional color filters, such as a warming filter.

information taken from dummies.com