"Medium tele macro lenses are among the most popular prime lenses - they are long and fast enough for decent portrait photography and offer a sufficient working distance during macro sessions compared to shorter macro lenses. Other than that they tend to offer an outstanding image quality and all that for an decent price tag. The popularity among customers is also a reason why we are seeing faster than average product life-cycles. In this review we will have a look at the Sigma AF 105mm f/2.8 EX DG HSM OS macro. Its predecassor was quite successful already and this new version is offering a couple of innovations such as an optical image stabilizer and especially a constant physical length across the focus range. As such it competes with the very comparable Canon EF 100mm f/2.8 USM L IS. It is about 20% cheaper than its mighty rival but it does not feature a weather sealing like the Canon lens."
Via Philippe Gassmann