Accurate exposure begins by correctly setting the lens aperture and shutter speed in relation to each other. You can set the exposure yourself manually or let the camera do it for you. The manual method requires either a separate hand-held light meter or you can use the one that’s built in. For 90% of photographs made, the metering systems inside digital cameras do a fantastic job in producing correct exposure but its those last 10% that’ll kill you, so sometimes you have to shift into manual mode.
Manual mode is for shooters who would rather drive a car with a stick shift than an automatic transmission. That’s because there are lighting situations that can confuse even the most sophisticated automatic exposure system. Manual exposure can be especially helpful are required with high subject contrast and strong backlight, but also when a specific mood is desired. (Consult your manual for the specific controls that adjust aperture and shutter speed.)
Some purists claim that manual exposure mode is the only one to use but I only use manual exposure mode when working under extreme lighting condition or in the studio with electronic flash, such as this portrait made with a Canon EOS 5D and an exposure of 1/50 sec at f/9 and ISO 100 that was made in my in-home studio. I usually use a fairly slow shutter speed to pick up some of the ambient room light and a smallish aperture to maintain sharpness throughout the portrait.
Tip: Many cameras also offer a Bulb mode where the shutter stays open as long as the shutter release is pressed. This allows you to make really long exposures for subjects such as holiday lights or fireworks or special effects such as images of carnivals and amusement parks. Time exposures like this should be made using a sturdy tripod and you can further reduce the risk of camera shake by tripping the shutter using a cable release.