I need an afforable macro lens - Advice Please

[ddt0725]

I have thought about the Tammy 90mm but this statement on Photozone is what stops me from purchasing it ...

"Typical for most macro lenses the Tamron AF 90mm f/2.8 SP Di macro performed very good to excellent in the lab. The lens is already very good in the center at wide-open aperture with marginally worse corners. The lens reaches its peak performance at f/5.6 where is scratches the resolution limits of the 8 mega pixel sensor of the EOS 350D. Beyond f/8 diffraction is the limiting factor - a physical barrier where no smart lens design can help. Generally you should avoid stopping down beyond f/16."

Many times for macro shots, I stop down to f/8 and beyond. So, I always thought this lens wouldn't be a good choice.

This is their statement for the Sigma 70mm ...

"Macro lenses tend to be stellar performer thanks to a usually very conservative max. aperture and the Sigma follows this tradition. The resolution characteristic is generally excellent straight from f/2.8 all the way down to f/11 with a slight peak in the f/4-5.6 vicinity. Due to the usual diffraction effects the resolution is reduced to very good levels at f/16 and good quality at f/22."