From 300mm telephoto to 800mm ultra-telephoto this new lens provides a constant fast maximum aperture and is optimized for digital SLR cameras.
The Sigma 300-800mm f/5.6 EX DG HSM is an extreme telephoto zoom lens, and ideal for nature/outdoor or sports photography. This lens provides a relatively large constant f/5.6 maximum aperture at all focal lengths.

The use of Apochromatic design and 2 ELD (Extraordinary Low Dispersion) glass elements give full correction of chromatic aberration and provide a high level of optical performance. The AF drive for the Canon EOS, Nikon and Sigma mounts are equipped with the silent, responsive and high speed Hyper Sonic Motor and provides fulltime manual focus override.

The improved DG lens design corrects for various aberrations. This lens is specially coated to get the best color balance whilst cutting down on ghosting caused by reflections from the digital image sensor. The lens provides the utmost correction against lateral chromatic aberration, which is a serious problem for digital SLR cameras.

It is also possible to use this lens with Sigma 1.4x EX and 2x EX Apo Tele Converters to convert this lens into an ultra tele-zoom lens, effectively converting it into a 420-1120mm f/8 or 600-1600mm f/11 lens. The lens materials used in this new lens are lead and arsenic free ecological glass.

• Hyper Sonic Motor provides smooth, silent AF with fulltime manual focus override
• The rotating tripod mount can be conveniently detached if required
• Apochromatic design and 2 ELD (Extraordinary Low Dispersion) glass elements give full correction of chromatic aberration and provide a high level of optical performance

Reviews

Sigma 300-800mm f/5.6 EX DG HSM Interchangeable Lens Review by ephotozine.com

This is a specialist lens, which only comes into its own in the fields of sports and wildlife photography and possibly some aviation uses. However, once it is in a situation where it is comfortable, there is not a lot that can touch it. With converters, it can match the focal lengths achieved by Digiscoping with an enormous leap in quality. Yes, it is a big, heavy lump and the absolute minimum is a sturdy monopod or tripod to support it and, if you have one, a Sherpa to carry it for you. Failing that, mount it on the tripod, put the beanbag on your shoulder and it balances quite well. The case protects it but proved useless for carrying it! I’ve used it on 4,6,10 and 12mp cameras and all the results are stunning.