I can easily say this lens has outperformed all the previous Sigma lenses that I have tried. I think Sigma is aiming big in this one giving the impression you don’t need a prime lens to shoot prime photos. This lens happens to be the only lens in the world that maintains 1.8 aperture through-out zoom range right now.
Only a few lenses come with an aperture this wide. This is beneficial because it lets more light pass through the lens before taking a photo but it increases depth of field; you have to be very specific when taking photos with this aperture. The narrowest aperture on the lens is 16 which isn’t bad but standard lens’ normally have 20 – 26 aperture.