Canon EOS 7D Instruction Manual page 150

Live View Shooting Cautions
Notes About the Live View Image
Under low or bright light conditions, the Live View image might not reflect
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the brightness of the captured image.
If the light source within the image changes, the screen might flicker. If
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this happens, stop and resume the Live View shooting under the actual
light source to be used.
If you point the camera in a different direction, it might throw off the Live
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View image's correct brightness momentarily. Wait until the brightness
level stabilizes before shooting.
If there is a very bright light source in the picture, the bright area might
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appear black on the LCD monitor. However, the actual captured image
will correctly show the bright area.
In low light, if you set the [6 LCD brightness] to a bright setting, noise
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or irregular colors may appear in the Live View image. However, the
noise or irregular colors will not be recorded in the captured image.
When you magnify the image, the image sharpness may look more
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pronounced than it really is.
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