Bill, I agree with you that a nominal f/1.9 lens that t stops around t/3.3 seems very odd. But K40 doesn't lie. I was very shocked by the disagreement between my 4008ZM and, e.g., my Nikkormat.

As for the R10, well, as I said I'm not the only person to have been surprised by its lens' poor transmission. On the other hand, the lens has several gazillion elements and light is bled for the viewer and for the meter. See , the lens' cross-section is at the bottom of the page.