To get the very best quality from your camera, use the lowest iso setting (the sensitivity of your cameras sensor) on your camera that you can.
The lower the iso setting the better the quality, and in particular the lower the digital noise.
Digital noise looks like random pixels of different colours in your image, and generally the better the camera, the lower the digital noise.
Be aware that low iso settings mean slower shutter speeds and wider apertures.
As a general rule, on a bright sunny day use iso 100, and on an overcast day use iso 400 to 800.
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