Originally posted by MikePerham Even if you are using a smaller aperture than the max aperture of a faster lens, the faster lens will give you a better viewfinder (brighter) image and make composition and focus a lot easier. For that reason I go with the pro grade zooms that offer constant f2.8 ...they also have better build quality.
I second that. I was comparing the lenses in low light and the Tamron is really dark. I have no complaints about build quality, though. It works and feels a lot better than the price tag would have you believe. I think I paid $135 for it.
The image quality is not going to match a prime lens, of course. In the example given, even though the superzoom is about one stop down from wide open and not at its zoom extremes, the prime is over four stops from wide open and probably at its best.