Canon MG6400 series Online Manual page 108

Important
If you double the resolution, the data size of the scanned image quadruples. If the file is
too large, the processing speed will slow down significantly, and you will experience
inconvenience such as lack of memory. Set the minimum required resolution according
to the use of the image.
Note
When you will be printing the scanned image by enlarging it, scan by setting a higher
resolution than the recommended one above.
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