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."

[Daniel Browning]

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

"[...] 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.

You understood photozone to say "Generally, you should avoid stopping down beyond f/16 *on this particular lens*". But they didn't mean that particular lens -- they meant every lens from every manufacturer. For whatever reason, they don't mention the same thing on other lens reviews, but it's not because of anything specific to the Tamron lens. In any case, as you already know, you can get perfectly acceptable results from f/22 and beyond, so ignore that particular bit of advice.