Quote Originally Posted by Dan Fromm View Post
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 http://imaging.nikon.com/history/cou...19-e/index.htm , the lens' cross-section is at the bottom of the page.
It's quite an elaborate design, for sure. I would not normally think of a beam splitter as part of the lens, but in these cases it definitely is, so should properly affect the T-stop. I'd guess that the beam splitters are the predominant reasons for light loss, but perhaps only Nikon knows for sure.