Chiang Mai Photo Workshops

Creating a ‘Correct’ Exposure

Choosing that moment in time to press the shutter button where I have the right lens on my camera, my composition is pleasing and the light is perfect is a moment of joy. However, that moment of joy can be short lived if I have not set my exposure ‘correctly’. I say ‘correct’ with inverted commas because exposing an image is quite a matter of creative choice.

Auto modes on cameras read the light and calculate exposure to give satisfactory results much of the time. Modern light meter technology with multi-point 3D balanced matrix wizardry figures out what’s going on in the shadow areas and highlights in front of the camera as the shutter button is half way depressed. Once the camera’s shutter speed, aperture and ISO are set to match the light reading and the shutter button is fully pressed, an image is captured. This is leaving a lot of decision making up to the camera.

Photographing in conditions where the light is fairly even and there’s not much contrast, the camera can generally choose a correct exposure. Shooting in very bight light, with dark shadows, or very low light with not much contrast, your camera may start to return less than satisfactory exposure results. This is when it pays to know a little more of how the camera’s light meter works, and have some understanding that your camera’s sensor is not so capable of ‘seeing’ as your eyes are. Our eyes can see detail in both areas of shadow and areas of brightness far more readily than our cameras can (usually.)

When the light is even and the scene is not highly contrasty, the camera’s light sensor will make a correct exposure of your composition quite effectively. Photographing a scene with bight light and high contrast some areas of the composition will be under exposed and/or over exposed due to the light ratio being so vast. Setting the exposure for mid way between the darkest and brightest part of the composition is one option, this will result in a reasonably well exposed photograph. Alternatively the exposure can be set for either the bight or the dark areas of the composition – this technique can open up whole other realms of creativity.

I shoot on manual most of the time and I alternate between two light meter settings frequently, matrix and spot. Cameras generally have three light meter settings – matrix, center weighted and spot. Set to matrix the camera will read light from the whole composition. On the center weighted setting the camera will read from about 60% circle from the middle of the frame. The spot meter setting reads from about a 5% area where ever your camera’s focus point is set to. These metering settings function the same way when a camera is set to manual or and auto mode.

Most people tend to leave their light meter set to matrix and find it works well. I love using the spot meter to read specific areas of my composition, especially when I am making a portrait. I need to know the exposure on the subject’s face will be correct. If I use only the matrix setting and the background makes up a significant part of the composition and is either very bright or very dark it is likely that my exposure will be disappointing. Setting my light meter to take a spot reading off the subject’s face will show me to set the shutter speed, aperture and ISO. Leaving the background under or over exposed can help create a strong portrait too.

The photo below I used the spot meter to take a reading from my subject’s face. Because of the strong back lighting and dark background a matrix or even center weighted reading would most likely have provided a disappointing result.
Young woman with an elephant at Mae Sa Elephant Camp

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