What is Camera Metering?
Before we even start understanding metering modes, we will need to understand what metering is all about. Digital cameras have a light meter inside them. This light meter’s job is to ascertain the amount of light that is being reflected from a certain scene. This inherent system is however flawed because it never measures the incident light.
Metering systems by different manufacturers
Canon and Nikon, the two largest digital camera makers use different acronyms to express the built-in metering modes in their cameras. However, by and large, these contrasting names notwithstanding, they mean the exact same thing. So what is Evaluative Metering as per Canon becomes Matrix Metering as per Nikon.
How it Works
When you look through the viewfinder you will notice there is a small scale which appears similar to the scales of a thermometer. If you are shooting in manual mode the meter will look at a scene and indicate in the viewfinder (and the top LCD) whether it is too bright or too dark. The indicator on the scale will move to either right or left. In manual mode you can then change either the aperture value or the shutter speed to compensate and bring the indicator back to ‘0’. Basically you are following what the meter is suggesting.
In Aperture and shutter priority modes, when you choose the aperture value and the shutter speed, the meter assesses the shutter speed and the aperture value respectively.
Understanding the metering modes – Evaluative Metering
The first metering mode is the Evaluative or the Matrix metering. This system takes into account the quantity of light that is being reflected across the whole scene and thus calculates the required exposure to make it 18% grey.
Spot metering system uses only a tiny bit of the scene for the purpose of metering. Spot metering is suitable when faces are involved in a scene and or when you want to highlight a face in a back-lit situation.
Center-weighted metering denotes when an area larger than spot metering is given more relevance to meter a scene but the whole scene is nevertheless considered to perfectly calculate the exposure.
When the Metering System Gets it Wrong
It is after all a through the lens (TTL) metering of the reflected light and it is bound to get it wrong at times. So, in a situation where the camera sees too much light (a sunset or sunrise) it tries to under expose incorrectly. Again, a snowy landscape scene will fool the meter into thinking that there is too much light and it will try to incorrectly underexpose to achieve middle-grey. These are the situations where none of the metering systems will work properly and the photographer has to manually adjust the exposure in camera, even if it means going against what the camera thinks is correct.
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Wanderlust at heart and a shutterbug who loves to document his travels via his lenses; his two passions compliment each other perfectly.
He has been writing for over 6 years now, which unsurprisingly, revolve mostly around his two favorite pursuits.
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