Just the 'absolute' nature of your comment. Implying that because the tele is longer it must be worse in low light. It's worse in low light because of the smaller aperture, not because its focal length is longer.
Ah, well I wasn't intending to speak in absolute terms. I know that the reason the tele is worse in low light is (in part) because of its higher f-number. But nine times out of ten, if you look at two similarly priced, similar quality lenses for the same camera system, a telephoto lens is going to have a higher f-number than a wide angle or lower focal length lens. That's not to say you can't make an f/1.8 telephoto lens that matches some wide angle lenses, but it's much harder to make and probably going to cost thousands of dollars, whereas an f/1.8 wide angle lens could be had for a couple hundred because it's much easier to make lenses with lower f-numbers the shorter they are, which should be obvious. It's easier to get more light to come through a short tube than a long tube.
Oh, and as someone pointed out on the previous page, in the case of the 7 Plus, the telephoto lens actually does have the LARGER entrance pupil despite having a higher f-number. I think some confusion is coming from the fact that some of us, me included, were incorrectly using the terms aperture and f-stop interchangeably. While these terms are related, they are two different things and can't always be used interchangeably.
Jake by Rick McNelly, on Flickr
Naia B&W by Rick McNelly, on Flickr
