Metering...What You Need To Know

Another buzz word I always seem to bump into when doing research is metering. I'll be honest, the word frightened me a bit at first. No kidding! It just seemed so technical a term that I avoided it for a while. Now that I'm feeling more confident in my abilities as an amateur photographer, I decided to tackle the metering monster. As it turns out, it doesn't bite! So, what's the big deal about metering?

Metering is the "Big Daddy" of exposure. Your camera uses its light meter to determine if the available light for the shot is adequate to create the right exposure. It uses this information along with a combination of aperture, shutter speed and ISO to calculate the appropriate exposure for the scene. The light meter indicates whether a subject is either overexposed or underexposed by displaying a row of bars beneath the numbers on the meter. To obtain your light reading, point the camera at the scene you are about to shoot, press the shutter release button halfway down and take a peek at your light meter. Bars that point toward positive values are telling you that your shot will be over exposed (too much light) and bars that point toward negative values means your shot will be underexposed (too dark). You will then need to adjust shutter speed, aperture and ISO to obtain the correct exposure indicated by a single bar displayed beneath the zero.

<----------Negative values - Camera Light Meter - Positive values--------->

Digital cameras make it easy to adjust  metering by featuring different metering modes that give you control over where the camera selects its light reading from. There are four main metering modes: matrix, center-weighted,  partial, and spot metering.

    Matrix Metering       Partial Metering         Spot Metering       Center-Weighted
METERING MODES 

This mode takes into consideration the brightness of your scene from different areas and determines the average of the total light readings. It's the camera's default setting and the mode that is most commonly used because of its reliability in generating the best exposure in different settings. It is best used when shooting landscapes that have an even distribution of lighting. It uses its light readings to correctly expose the entire scene. 

Evaluative/Matrix Metering: The camera attempts to give equal exposure to the entire scene.

In this mode, the camera directs its attention to a considerably small area of the photo that is to be exposed and ignores anything else in the scene. What a snob! It is quite similar to spot metering, but covers a larger portion of the frame. Use when you want to make your subject the main focus of the photo.

Partial Metering: The camera focuses primarily on the subject of the shot.

When using this mode, the camera selects a very small part (2-3% of the frame) of the scene at the center to select its exposure value. Use when shooting a very dark or very bright subject and you want to have only one small part of your photo correctly exposed. This setting is great for portraits when your subject is back lit (the sun is at their back) because it exposes the face which would otherwise be dark in this setting. Make sure that your subject is in the center of the frame to be properly exposed.

Spot Metering: The camera zeros in to calculate the exposure for a smaller area of the subject.

Center -Weighted Metering gives importance or "weight" to the center of the scene while taking light readings from the surrounding areas as well. It's important to note here that the camera takes light readings from the center of the frame and not where you have placed your focus point. Make sure that when using this mode, your subject is in the center of the frame to be properly exposed. Center - weight metering is good to use for portraits and scenes where the background is dark or light because it is not affected by the variations in light in the background.

Center - Weight Metering: Evaluates the center of the frame to calculate exposure.

Remember: The camera can be tricked when calculating exposure. If after viewing your photo and you notice that it is still under or over-exposed, make use of the exposure compensation feature to get it just right. Flash can also be applied to fill in shadows or dark areas of your shot. Each of these modes is best used in certain situations. Read below to find out when to use them effectively:

                Setting                                                                                                  Use

Sunny day, no light or dark areas                                                               Evaluative/Matrix metering

Portraits or focusing on a particular subject                                               Partial/Spot metering

Your subject is back lit (sun or light source behind them)                         Center-Weight metering

In the diagrams below, the area in green shows where the camera takes its light readings to determine exposure.

Professional photographers use a device called a "digital light meter" to help them as well. It's quick, easy to use and is quite effective in giving you the settings you need to deliver the correct exposure.

Digital Light Meter

Photo courtesy of Wikipedia

For additional reading, have a look at: http://mansurovs.com/understanding-metering-modes.
Well, there you have it! One more tip to add to your bag of tricks. I hope that this information has helped you. If it has, tell me all about it!!