I've been working on an explanation of K in the B&W Film, Paper, Chemistry forum. The thread is "Is the K factor relevant to me or should I cancel it out?" and is on page 3 at the moment. I'm almost finished with it, so it should cover what you want.
One thing you will find is that the assumptions of 18% and 45 degrees aren't accurate. K=1.30 is only 1/6th stop difference from K=1.16 which is considered normal for average conditions.
Last edited by Stephen Benskin; 02-03-2011 at 09:52 PM. Click to view previous post history.