Category: Photography Tuition

Camera Exposure and Light Metering

Camera Exposure and Light Metering

How do we make a photo which is the brightness that we want? There are a number of different methods which I will cover in this tutorial, starting with how do determine this without a light meter, then looking at the incident light meter, the reflective light meter, and the Zone System. Finally we make some other important observations about the range of brightness the camera can record.

[Please note that this post is available as a PDF where the tables and illustrations can be seen at there correct size – click here]

The Sunny 16 Rule

Back when there were only film cameras and very few photographers had light meters, the manufacturers of film supplied a tiny slip of paper with recommended exposure settings for the light conditions. So for example, the guide for a 200 ISO film looked like this…

Lighting conditions and weather Shutter Aperture
Bright sun/  Shadows distinct or hard 1/200      f/16
Slightly overcast / Hazy / Soft shadows 1/200      f/11
Overcast cloudy / Faint shadows 1/200      f/8
Very overcast and cloudy / Open shade from sun / No shadows 1/200      f/5.6
Around sunset time / Deep shade 1/200      f/4
Just after sunset / Bright neon lights 1/200      f/2.8

 

You can see that the shutter speed recommended is 1/ISO. This guide is just as relevant today with modern digital cameras, where we can change the ISO for every photo. It is a reliable and simple starting point to getting a good exposure without using a light meter.

Measuring Light

There a two very different words we use to explain ‘brightness’[1] in photography… illuminance and luminance.[2]

  1. Luminance describes the measurement of the amount of light emitting, passing through or reflected from a particular surface from a solid angle. It also indicates how much luminous power can be perceived by the human eye. This means that luminance indicates the brightness of light emitted or reflected off a surface.
  2. Illuminance is a term that describes the measurement of the amount of light falling onto (illuminating) and spreading over a given surface area. Illuminance also correlates with how humans perceive the brightness of an illuminated area. As a result, most people use the terms illuminance and brightness interchangeably which leads to confusion, as brightness can also be used to describe luminance. To clarify the difference, illuminance refers to a specific kind of light measurement, while brightness refers to the visual perceptions and physiological sensations of light.

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