Crystallographic data file formats
MAREdit
A MarCCD file is a TIFF image. The first 4096 bytes contain the header in a simple format, where the crystallographically interesting stuff starts after byte 1024. Have a look here for a description of the format: http://www.rayonix.com/site_media/downloads/header.pdf . In $CCP4/lib/DiffractionImage/MAR you will see a header file which describes the structure of the TIFF header.
ADSCEdit
uses the SMV file format