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Noise and sharpening

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Keep your digital images noise free

Digital noise is one of the biggest problems faced by digital photographers. The good news is that you can avoid it. The first thing to do is consider your ISO setting. Higher ISO settings tend to display more digital noise than digital images taken at lower ISO settings. The fix is to lower this setting to ISO 200 or ISO 100, if possible, which reduces the camera's sensitivity to light. But this isn't always the cause of noise. While avoiding noise might be impossible, here are few other suspects to consider when trying to quiet down your noisy images:

  • Underexposed images. If an image sensor can't get enough light to capture an accurate reading, it's likely to misinterpret the signal and produce noise. You can fix this by increasing your exposure compensation or your shutter speed.

  • Blue skies. For very technical reasons, digital cameras and blue skies don't get along. First, the subtle color shifts and large areas of uniform color can cause noise to develop as the sensor tries to reproduce the gentle gradient. Another factor is the infrared filter on most CCD sensors, which tends to increase the sensitivity to the blue end of the spectrum. There isn't much you can do to fix this outside of an image-editing program, but camera technology is improving every day!

  • Automatic sharpening. Some cameras let you apply a sharpening filter to your images during capture, which can emphasize noise. Try reducing the amount of sharpening or simply turning off this feature.

  • Shadows. When a digital camera evaluates a scene, it adjusts the exposure to get the best overall image quality. However, shadows often become noisy, especially when a majority of the scene is bright. Consider using your camera's manual settings or slightly underexposing the shot. You can lighten up the remainder of the image later in your image-editing software.

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