I'm a beginner in photography and I'm wondering what metering is? Using a Sony a3000?

1

Cameras have a built-in light meter that reads reflected light off the subject.

It's this that determines the ISO, aperture and shutter speed that you (or the camera in Auto or semi Auto modes) uses to set the correct exposure.

The metering system usually has 3 options;

- spot - this only meters for a very small area in the viewfinder (usually the centre) and ignores everything else.

- centre weighted -this meters a bigger area but still giving emphasis to the central part of the viewfinder.

- matrix - this gives an average value across the whole viewfinder.

The light meter is viewable as a scale with a pointer or marker, but may not be visible in the viewfinder unless you are in Manual exposure mode.

All light meters work on a mid grey tone - that means that if your subject is not a mid-tone it may be slightly under or over exposed, so you'd need to dial in some exposure compensation.

We are generally after a faithful image when we take a picture. The quality of the resulting image is highly dependent on how much light plays on the image sensor during the exposure. If too little light or too much light plays on the sensor, the picture will be substandard. Over the years photographers made a quest to find better ways to get the correct exposure. In the early days we used tables and charts that told us how to set our cameras for sunny, cloudy bright, and overcast conditions. These were OK but we took delight when the electric light meter arrived in the mid 1930’s. We all carried a large light meter and we all measured the scene and the subject and the lights and used a built-in sliding scale to tell us how to set the camera. Next the light meter was miniaturized and inserted into the camera. Now we could point the camera and take a light measurement. Next cameras gained computer chips. A modern camera with built-in light meter and its computer logic takes a light measurement and pre-sets the camera as you press the go button.

No need to worry about light measurements and metering, you camera does it all in automatic mode. Can you do a better job getting the exposure right? Sure, a human is smart and a human can learn by studying. So if you want to be a serious photographer. You need to start reading the manual and books on photography and exposure. If you are willing to put in this effort, your picture taking skills we leapfrog and you will be in line for blue ribbons.

All cameras meter the light reflecting off of the subject. And, all meters are calibrated to produce an exposure that will render that light as a middle-gray tone. With that in mind, you can understand why metering off of something that is already middle gray will result in a perfect exposure. However, metering off of something that isn't such as white snow or a black car, will result in either the image being over or under exposed.

Cameras have various metering modes. Most of the cameras available today use some kind of evaluative metering or multi-segmented metering. This is where the camera meters the light is multiple areas in the frame individually and comes up with a lighting pattern. It then compares that pattern to a database and tries to figure out what the scene is. Dark center and bright around the edges could be a person standing inside a building in front of a window. Middle-toned bottom half of the frame and brighter top half could be a landscape. This kind of metering has evolved over the past few decades to be rather accurate. This, as with any and all other types of metering modes, can be used with any exposure mode such as program, aperture and shutter priority and, of course, manual mode.

You typically have additional metering modes such as center weighted, and my favorite, spot. Center weighted meters off of a large central area. Spot, as the name suggests, meters off of a very small area, usually seen in the viewfinder as a small circle in the center. This allows the photographer to make very precise meter readings off of small portions of the scene. For example, in center weighted, the meter may get fooled by someone standing in front of something bright like a window. However, spot allows you to meter off of a small area like just the left cheek to find the exposure for the highlight on the left side of the person's face and then meter off of the right cheek to get an idea of how broad the exposure range is. The exposure range is just the range, in stops, from the brightest to darkest area. Knowing this will tell you if your sensor or film can handle the scene or if you need to choose between loosing detail in the highlights or shadows.

While using a meter the measures the light reflecting from the subject often requires adjustments because many things can reflect more or less light than a middle-gray object, using a meter that measure the light FALLING onto the subject does not. Using an incident light meter measure the light falling onto the subject so you don't have to worry about how much light your subject is reflecting. It's a type of metering that is only found in hand-held light meters such as those from Sekonic. Take a look at one and you'll see a white dome. It's the white dome that is used with the metering cell to measure the ambient light.

That's about all there's to it. Measure off of the subject, and determine if the subject has a middle gray tone or not. If not, then increase the exposure to make white subject white and decrease the exposure from the indicated exposure to make dark subjects dark. Not doing anything will result in dingy whites and murky blacks.

Metering is using the camera's in-built light meter, or an external one, to determine the light intensity that the camera sensor will see and from that you can determining the optimum camera exposure settings for whatever type of photo you want to take or effect you want to achieve.

It's at the heart of photography.

2

Metering is what you use to determine the correct amount of light needed to produce your image.

Through use of metering you set aperture, shutter speed and ISO.