how does Ole know how to do these things?!! (probably did it his head, besides.)

doing it the old fashioned try it and measure with a ruler way, I have a good correlation with Ole's number. A total extension of 15 inches from the negative to the "lens nodal point" (I would have said middle of the lens, but Ole has taught me to say "lens nodal point") with my 210 Componon-S gives me a 6x9 inch print.