Canon EOS 5D Mark IV L-series Zoom Lens Kit Owner's Manual

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 Appending Dust Delete DataN
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After the Dust Delete Data is obtained, it is appended to all the JPEG 
and RAW images captured thereafter. Before an important shoot, it is 
recommended that you update the Dust Delete Data by obtaining it 
again.
For details about using Digital Photo Professional (EOS software, 
p.598) to erase dust spots, refer to the Digital Photo Professional 
Instruction Manual (p.600).
The Dust Delete Data appended to the image is so small that it hardly 
affects the image file size.
Dust Delete Data
Be sure to use a solid-white object such as a new sheet of white paper. If the 
object has any pattern or design, it may be recognized as dust data and 
affect the accuracy of the dust deletion with the Digital Photo Professional 
(EOS software).