Understanding Light Metering System

Understanding light metering system is one of the most fundamental knowledges in digital photography as it gives you a starting point for determining exposure settings in different lighting situation.

Understanding Metering System

Basically all the metering systems do is tell you how much light is available. They don’t tell you about the brightness range within the scene (aka contrast), or where the areas of brightness and darkness occur and how much of the frame they occupy. This is why it’s important to understand the metering properly, to be able to evaluate the scene to determine whether the meter’s recommendations will need modifying or overriding using one of the manual’s camera exposure controls. This may well be necessary if you want to apply your creative mind with your exposure control (you can delibeartely under- or overexposing to give a particular visual effect)

Understanding Metering  in Snow Scene

The example is the snow scene. When shooting on snow, the meter will recommend exposure setting which give the equivalent of an 18 percent grey tone, which will give you very blueish-looking snow. To avoid this and to get white snow in your photo, you need to give more exposure as much as 1 or 2 stops than the meter recommends. For example if the camera’s meter is recommending an exposure of 1/250 seconds at f/16, you might want to use 1/250 at f/11 (+1stop) if you need to freeze an action or 1/125 at f/16 (+1stop) if you need more depth of field.

Metering Systems

Many digital cameras today offer a choice of metering methods which can be used in different lighting situations or for different creative effects.

Multi-zone aka multi-pattern metering aka Matrix metering (in Nikon cameras)

Multi-zone-metering

How does it work?
The frame is broken up into a number of zones or segments and the brightness level of each is measured separately. The information is then compared with a databse of scenes stored in the camera to determine which pattern fits best, and which zones should be used as the basis for the exposure recommendations.

When do you use it?
It works very well with scenes with a wide brightness range, but where there is roughly equal amounts of bright and dark tones. It’s also perfect when you are unsure exactly which metering system to use.

Centre-Weighted-Average metering

Centre Weighted Metering

How does it work?
The system will average all the light and dark areas in the frame, but then weights this reading more towards the brightness level predominant at the centre of the frame.

When do you use it?
This is the excellent system for general wildlife and people portrait where a centrally weighted average is required. However, don’t use it if you don’t know how to operate the exposure lock on your camera and your subject isn’t located centrally and the background is either very bright or quite dark as this meter will give an innacurate reading that would result in either under or over-exposure image.

Spot metering

Spot-metering

How does it work?
Your metering system concentrates all its measurement (or weighting) on a very small area represented as a spot in the centre of the viewfinder frame. Typically spot meters cover only two to four percent of the total frame area.

When do you use it?
Use it when you have understood the principles of exposure control as ot will give you more accurate reading than the centre-weight system. However, don’t use it if you don’t know how to operate the exposure lock on your camera and your subject isn’t located centrally and the background is either very bright or quite dark as this meter will give an innacurate reading that would result in either under or over-exposure image.


See also: Photography Tips





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1 Comment »

Comment by Mrali Subscribed to comments via email
2008-12-01 01:02:00

Thanks for the explaination.
Is it OK to shoot for portoraits while the lights is on?

 

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