What is the sigma 28 70mm f 2 8 dg dn contemporary good for?

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From Sigma 28-70mm f/2.8 DG DN Contemporary: Sigma 28-70mm f/2.8 DG DN Contemporary: A zoom lens by Sigma for Full frame cameras, 28-70mm f/2.8. A small, light f/2.8 standard zoom. Specs - Maker: Sigma - Focal length: 28-70mm (zoom) - Maximum aperture: f/2.8 - Made for: Full frame sensors - Mounts: Sony E, L-Mount - Stabilised: no - Autofocus: yes What it frames like - On full frame (Sony E, L-Mount): as marked, 28-70mm. - On APS-C (Sony E, L-Mount): like 42-105mm on ...

From Lenses: Aperture: The f-number says how wide the lens opens. Smaller numbers let in more light: f/1.8 lets in about ten times as much light as f/5.6, more than three stops. A wide aperture means faster shutter speeds in dim light and more background blur. Zooms with a constant aperture, like a 24-70mm f/2.8, keep the same exposure throughout the zoom range; cheaper zooms get darker as you zoom in.

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