Canon PowerShot G12, Selecting the Proper ISO

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When shooting most landscape scenes, the ISO is the one factor that should only be changed as a last resort. While it is easy to select a higher ISO to get a smaller aperture, the noise that it can introduce into your images can be quite harmful (Figure 7.2). The noise is not only visible as large grainy artifacts; it can also be multicolored, which

A high ISO setting created a lot of digital noise in the shadows (left). When the image is enlarged, the noise is even more apparent (right).
Figure 7.2 A high ISO setting created a lot of digital noise in the shadows (left). When the image is enlarged, the noise is even more apparent (right).

further degrades the image quality. Take a look at the image on the left, which was taken with an ISO of 1600. The purpose was to shorten the shutter speed to avoid camera shake in early evening light. The noise level is not only distracting, but also introduces a lot of color.

Now check out another image that was taken at the same time but with a much lower ISO setting (Figure 7.3). As you can see, the noise levels are much lower, which means that my blacks look black, and the texture you’re seeing is the wall, not the noise from the camera’s sensor.

When shooting landscapes, set your ISO to the lowest possible setting at all times. Between the use of image stabilization (if you are shooting handheld) and a good tripod, there should be few circumstances in which you would need to shoot landscapes with anything above an ISO of 400.

By lowering the ISO to 80, I was able to avoid the noise and capture a clean image (left). Zooming in shows that the noise levels for this image are almost nonexistent (right).
Figure 7.3 By lowering the ISO to 80, I was able to avoid the noise and capture a clean image (left). Zooming in shows that the noise levels for this image are almost nonexistent (right).