I'm considering getting one of these three lenses, I'd like to here others opinions/experience on these lenses. Nikon 10.5 mm DX f/2.8 G IF-ED AF Lens Tamron 200-500 mm SP AF F/5-6.3 Di LD (IF) Zoom Lens for Nikon D-Series Sigma 170-500mm APO F5-6.3 DG AF Zoom Lens for Nikon AF A lot of people are telling this should be my next lens: Sigma 12-24 mm f/4.5-5.6 EX DG Aspherical Lens for Nikon AF But I don't see me using that alot and the 10.5 is faster, if I go below 18 I'm going to be doing horizon's and sunsets and 2.8 vs 4.5-5.6 I can crop out anything I'd get 12-24 right? Someone also suggested a good macro lens Which I do get a lot of butterfly pictures, would it be more practical to get a macro lens or just use one of the existing I have and/or buy one of my other three and get a macro filter? And are macro filters all that great? thanks for any advice in advance.