I made some shots in my room during the evening with the room light which was not very bright with those two lenses (Nikon 24-70mm 2.8 and Nikon 50mm 1.8). Both lenses were set to 50mm @ f2.8 and the same shutter speed. What I have found is that the images produced with 50mm were somehow brighter than 24-70. So was it that the physical length of the lens that affected the intensity of light coming to the camera sensor? or it was because that 24-70 has more glass elements in the lens which could block some friction of light? Is it normal? thanks!