Man....i have alot of questions. I'm new though, so hopefully the number of them will decrease! I have noticed that alot of people with the NIKON and Canons have 3rd party lenses, ie. Sigma/Tamron etc. Are the Sigma/Tamron lenses just as good as the Nikon/Canon ones? I noticed the cost of lenses from the 3rd party are quite a bit cheaper...but does the quality go down as well? Im talking generally, I know some lenses will be alot better etc...but in general, how do the 3rd party lenses hold up against the manufacturers own lenses? Thanks.