I tried the "Isomorphous difference map” action and specified a file for input 1 containing F1+, F1– at one wavelength, and the file input 2 containing F2+,F2– at another wavelength. I selected the appropriate Labels for the columns containing the anomalous data. I then specified in "Advanced Options” to use anomalous differences instead of amplitudes. Will this procedure use the following coefficients for the difference Fourier? ( F1(+) – F1(–) ) – ( F2(+) – F2(–) ), alpha(calc) Can someone confirm if this is indeed what is calculated? Many thanks, Mark Saper __________________ Mark A. Saper, Ph.D. Visiting Professor at the Faculty of Medicine Hebrew University of Jerusalem Ein Kerem Jerusalem ISRAEL [email protected] mobile +972 52 815-0480 Powered by Mailbutler https://www.mailbutler.io/?utm_source=watermark&utm_medium=email&utm_campaign=watermark-variant-primary, the email extension that does it all