Metering Systems in a Typical Camera – Chapter 7
In this edition of my Free Basics of Photography Course I am going to explain the metering systems in detail. I hope you got a hang of what metering in a camera is.
In this chapter you’ll learn about the various metering modes that a typical camera has
To start with you should understand the following basic concept:
A camera’s metering system works under the assumption that the area under consideration for metering is 18% grey.In layman terms 18% grey is a mid-tone. So to get an appropriate exposure the photographer should meter from such an area of the scene which is a mid-tone.
In case the scene contains considerably lighter or darker tones the in camera meter will get fooled and provide for an incorrect exposure. For instance, if the photographer is shooting snow which is white (extremely lighter tone) by its color, the camera meter based on the assumption shall meter it incorrectly and assume that the snow color is considerably brighter than it actually is and render the image as under-exposed. this image will be darker than it actually is. Similarly a Black (extremely darker tone) object would be over exposed.
This does not mean that a photographer/you cannot rely on the in-camera meter. It’s just that the in-camera meter can be fooled and the photographer has to compensate for the exposure.
The Metering Modes
Multi-Zone Metering: Most of the cameras today utilize what is called the multiple zone metering. In this type of metering the scene is divided into multiple zones and each zone is metered separately each reading is then evaluated and the final exposure is arrived at. This type of metering is called as Matrix Metering/Evaluative Metering by different manufacturers. Almost any scene can be metered using multi-zone metering to get an accurate exposure.
Centre Weighted Average Metering: In this metering mode the meter reading is taken from the entire scene with a little higher weight given to the central area of the scene.
Spot Metering: In spot metering the meter reading is taken from from a very small area of the scene, typically 3% of the entire scene and based on this the final exposure is arrived at.
Partial Metering: Partial metering is similar to spot metering just that it uses slightly larger area of the scene. This area is typically 9% of the entire scene based on which the final exposure is arrived at.
I hope you are able to grasp the concept. Make sure that the metering is done from a mid-tone to avoid exposure errors. Different manufacturers uses different notations for the metering modes. You’ll have to look up to your camera manual to identify notation for the metering mode you are going to use.
Until the next chapter, enjoy working with the exposure meter.