Convenience and capability
If you've spent time shopping for lenses in the past, you know you are often forced to make a difficult choice. Do you get the go-anywhere composition convenience of a zoom lens, and trade off light sensitivity and the gorgeous out-of-focus backgrounds that large apertures can generate? Or do you go with a large-aperture fixed focal-length "prime" lens, and take its superior overall image quality in exchange for having to walk to the point where your framing seems right?
Now Sigma has created a lens for your APS-C sensor camera that gives you the best of both worlds. Its generous f/1.8 aperture throughout the entire zoom range means you'll have the light-gathering power to make quick work of a challenging lighting situation — and the shallow depth-of-field that leads to striking isolation of your subject in space. Plus, you'll have a variable zoom focal length that takes you from landscapes and group shots to a human-eye perspective on the world, perfect for everyday snapshots and candid portraits. The expert build quality of this lens means that you'll get the sharpness, clarity, and performance of a prime lens, while enjoying the creative flexibility of a zoom.