Dan, I said
Both is still true.Dan's figure is total out of proportion and so far I got no idea how it could be reasoned.
I did not know about any measuring you did, nor would I have doubt them, nor doubt I them now.
I beg your pardon that my statement/wording caused same aggrevation, that was not my intent.
That hint of being out of proportion as well as at self calculating was directed at Stone and his doubt about his modern Canon lens. So far rough calculations based on published typical reflection losses per surface ended in magnitudes of loss coherent with T-values of modern lenses. Furthermore there are statements from the industry including an old one by a Angenieux designer stating a loss factor for the geometrical f-stop of 1.1 .Your calculations depend on assumptions about loss/air-glass interface. Why do you believe your assumptions?