I currently have the Nikon 18-55mm kit lens that came with my D3100, but I am looking for something that will let more light in among the entire focal range. I have been eyeing the Tamron 17-50mm f2.8 as a potential option, but I am wanting to clear up just a few concerns:
1) I have heard the Nikon kit lenses are actually pretty decent in terms of sharpness, contrast, optical distortion, etc. How does this compare to the Tamron lens in question? I am buying the lens to get a higher f-stop but I don't want to do that at the expense of quality.
2) Since I have only shot with kit lenses, it is difficult for me to quantify just how much extra light will be let in with a f2.8 (compared with f3.5 on my kit lens). My goal is to take sharper indoor/low-light photos without the aid of flash or too much ISO. What is the real world differences between these f-stops?