Almost all cameras today have light meters which measure the light in the given composition and set an ideal exposure automatically. Most people depend on the light meter which is fine, but if you know how to control your exposures you can get some creative and sometimes greatly improved pictures.
Aperture and Shutter Speed
The two primary controls your camera depends upon for exposure are shutter speed (the amount of time the sensor is exposed to light) and aperture (the size of the lens opening that lets light into the camera). Shutter speeds are measured in seconds and more commonly fractions of a second. (1/2000 of a second is very fast and 8′ seconds is extremely slow). Apertures are measured in something called f/stops (a very wide aperture is f/2.8 and a very narrow aperture is f/19).
You might wonder why there isn’t just a constant shutter speed or a constant aperture so that you would only have to worry about one control. The reason is that even though they both designate the amount of light getting to the sensor they also control other aspects of the picture. Shutter speed, for example can be used to freeze subjects in midair with a fast speed or it can be used to blur water with a slow speed. Aperture controls the depth-of-field which is what is in focus in the picture. Aperture can be used to draw attention to one subject (like the flower on the right) by blurring the background with a wide aperture (low f/stop). Aperture can also be used to focus everything in a picture with a narrow aperture (high f/stop).
On most digital SLR’s (Single Lens Reflex) cameras today you can even change the sensitivity of the sensor when collecting light which is called the ISO speed. The common span of ISO speed is 100 to 1600. The higher the ISO speed the faster the camera collects light but it also adds more noise to the photograph than the lower speeds. For example if your trying to take pictures in dim light without a tripod you might want to raise the ISO speed in order to get a picture that’s not blurry. Most of the time you should keep it at a lower ISO speed if there is enough light, but it makes a big difference when there isn’t. Different cameras make different amounts of noise in photos so I would definitely experiment with your cameras ISO settings so you will know what to expect when it matters.
Most people dont experiment with or use the white balance function on their cameras. White balance is simply a function where the photographer has the option of designating what parts of a scene are white so the camera can adjust to the other color temperatures accordingly. Almost all digital cameras today give the photographer the option of manually setting the white balance which can sometimes be hard if you dont have a white or grey card. Many new digital cameras have a set of preset white balances for certain types of scenes such as snow or clouds. I have found that using the preset modes is almost just as effective as setting the white balance manually so I would definitely advise others to keep the preset white balance modes in mind when they are using their cameras.
Time of Day
The time of day is usually what determines how much light you are going to be working with. In the early morning and the late afternoon there will be less light than in the middle of the day. During this time there should be enough light for most kinds of exposures except if you are trying to catch an object in motion. If you are trying to catch sports photos or objects in motion you will have to adjust the aperture and maybe even the ISO speed (both of which are discussed in this article) in order to be able to use the necessary shutter speed. In the middle of the day (with typical weather) the light is very bright and you should be able to use any shutter speed or aperture that you want at the lowest ISO setting. At night it is a totally different story if you are not using flash. If you arent using flash and are taking photos at night probably with a tripod then you should set the ISO speed very high and you will need a very long shutter speed and a moderately wide aperture.
To become comfortable with exposure settings is a very difficult task. But if you master exposure enough to know what you should use for each scene, then you could become a much more professional photographer.