SB or any for that matter. Correct me if I am wrong, but in regards to the 42 v 50 mm obj. The difference will only be at lowlight? If you need around a 7 exit pupil then with the 50 you could use it at around 7 power v around 6 power on the 42? Is that it? Does anyone have any experience with the two sizes. Seems as though the lower mounting height and less weight of the 42 would be better? No? thanks in advance.