There are three concerns here:
1) caution: don't put retina searing light into the camera
2) to make sure you 'capture' enough light to make a photo without capturing to much, take a picture then check the camera's histogram. Any curve gets cut off along the top is overexposed (aka, clipped).
3) once you get the image into the computer, make sure it is not brightened further. Pixels that are already pure white won't get any whiter and pixels that are near white will be 'squished' into the same color (becoming inaccurate).
If your camera records RAW, software will often warn you on import (like with a red color) when colors are to bright or to dark. You can also reduce the exposure of a given image retroactively to fix such images.
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