I've cleaning and found this in an explanation of finding the SBR of a subject. This was in an old Xeroxed article that was missing many pages, so I have no idea where it came from anymore. Light - Dark+5=SBR 9-7+5=SBR7 That would make one photo I took a couple of weeks ago have an SBR of 13 Why would you add five to your difference. The explanation must have been on the missing pages. I just meter the highest and the lowest and figure the difference to get my SBR. have I been doing it wrong?