Canon EOS 1D MkII Instruction Manual page 26

The access lamp lights or blinks while the picture is taken, when
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data is being transferred to the memory card and when data is being
recorded, read, or erased on the memory card. Never do the
following while the access lamp is lit or blinking. Such actions may
destroy the image data.
It may also damage the memory card or camera.
· Shaking or banging the camera around.
· Opening the memory card slot cover.
· Removing the battery.
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After image capture, you cannot do any menu operation while the image
is processed and recorded onto the memory card (lit or blinking access
lamp).
When the memory card becomes full, the "Card Full" warning will appear
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on the LCD panel and in the viewfinder. Shooting will be
disabled.Replace the memory card with one that is not full.
Card Err
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If "
Card-full display
Memory card No.
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If you use a low-capacity memory card, it might not be able to record
large images.
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Microdrive cards are more vulnerable to vibration and physical shock. If
you use a microdrive, be careful not to subject the camera to vibration or
physical shock while recording or playing images.
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Do not touch the SD card's contacts with your fingers or metal objects.
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(Card error)" is displayed on the LCD panel, see page 119.
Card error display