Hi, long time since I posted on here. Hope someone can offer some advice. I have two lenses for my Nikon D80. A Sigma 17-70mm (f2.8-4.5) and a Tamron 70-300mm f4 - 5.6. For a while now I have noticed that photos taken with the Sigma don't seem to have as much colour as those with the Tamron. Do you think this is in my head or a artifact of the lens, or perhaps something wrong with it? I've been thinking of replacing the Sigma with a Nikon 18-105mm AF-S DX Nikkor f3.5-5.6 G ED VR. Do you think this would be a sensible move? Any comments appreciated.