Before we discuss about how to adjust exposure manually we need to understand what metering is. Metering is a process which depends on the light that is coming through the lens and how that light is evaluated by the camera’s metering system. DSLR cameras use a metering system known as TTL or through-the-lens. When light gets reflected of off a subject and enters the camera, it is evaluated and then the correct exposure values are set to get a perfect picture. However, as this is reflected light that is metered for and not incident light, and that means the reflectance of the surface is considered, even with some of the smartest metering systems in modern digital SLRs, you often get the exposure incorrect. This is why in some situations it becomes mandatory that you switch to manual mode and adjust the exposure manually.
Ever taken a picture of a bride at her wedding dress? Let’s say she’s standing against a neutral background wearing a beautiful milky white dress. You take a picture using the matrix metering mode and voila! The camera underexposes and making the picture look grayish. Again, take a picture of the groom looking dapper in a black suit and against a dark background. Mysteriously, the camera turns that into gray too! What’s happening is that the metering system, designed to make everything 18% gray, is either under-exposing or over-exposing to make sure that everything is that middle-gray tone. But you don’t want middle gray do you? No.
Taking Things in your Own Hands
So what’s the trick? How to rectify the problem? This is where manual exposure adjustment comes in to the picture, literally. Manual exposure denotes overriding the exposure values that the camera has set for the scene and entering what you think is right. You take the entire control in your own hands. Although, some photographers say that manual exposure compensation is not necessary and that you can still use exposure compensation in one of the creative manual modes such as Aperture priority and shutter priority, this is why you bought a DSLR isn’t it? You wanted to have complete control over what you shoot.
Adjust Exposure in Manual Mode
So, switch to manual mode and look through the viewfinder. You will see that there is a thermometer style meter. On a Nikon camera it has a ‘0’ in the middle. When the arrow is lined up with ‘0’ it means that the exposure is perfect. A Canon usually has an arrow instead of the ‘0’ and you need to line up the indicator so that the exposure is perfect. The exact dials and buttons are not discussed here because it is different in different cameras. Please check your camera manual to find out exactly what combination of buttons and dials you need to use. You will, however, need to turn the main mode dial to manual mode before using manual exposure compensation.
If the meter says your exposure is under, open up the aperture or slow down the shutter speed or increase the ISO to line up with 0. If the meter says you are over, select a smaller aperture, increase the shutter speed or reduce the ISO to balance it.