Sigma 17-50mm f/2.8 EX DC OS HSM is a standard lens produced since 2010 for APS-C format with focus via ultrasound AF engine with image stabilizer. Its constant opening and the autofocus engine make it the ideal choice for those who own entry level models. Chromatic aberrations are limited and it is possible to define this system as a handyman. The sharpness of the images is, even if it is not excellent, the escaped is good for a zoom of this level, very interesting. What connotes him is undoubtedly the value for money. The weight is not the best, in some ways the handle could be difficult and stingy. To take the photos in the focals of daily use is optimal, the lens tends to correct the defects by itself and this is a great help especially with close subjects. There are no back or front focus problems and work with extreme precision. It is good for all photographic genres thanks to the focal openings, from the portrait to the landscape allows you to always shoot even without stopping. The OS stabilization system allows you to have photos with longer times than normal. Ideal for: all those who want a stable, versatile, cheap and handy system. We are not talking about an excellence but an ally to always have on the bag for the most disparate situations. Perfect for a first kit.