How to shift "phase" of first column for image subtraction

[qtao]

Question: When perform subtraction of two images by Arithmetic Operations, I can not get a good result if the first column retention is tiny shifted. How can I shift the first-column phase of an image?

Answer:
If the tiny shift on Column I retention is caused by the difference of start Column I retention times of two images, you can prepend or crop the first column. See Cropping/Prepending/Appending for details here:
http://www.gcimage.com/gcxgc/usersguide/io.html#Import

In addition, for the phase shift of the second column separations, see here for details:
http://www.gcimage.com/gcxgc/usersguide ... ShiftPhase