I read in a old paper magazine "FOTO" here in sweden. They testet sony 100mm macro vs Sigmas 105mm macro.
accordning to their test the minolta/sony one was mediocre and not sharp until stopped down quite alot , but the sigma was sharp at full opening.
They also gives critque to online MTF testing, (SFR testing) which usually meassures the hole system, lens + body + raw converter, but their test meassures the true performance of a lens, regardless of body used.
Are there any substance to these claims ? And is sigmas macro actually better than minoltas? (sonys)