Sigma APO 300mm F2.8 EX DG HSM Lens

Two ELD glass elements reduce chromatic aberration to a minimum and also ensure sharp, quality images of high contrast. The new multi layer lens coating reduces flare and ghosting, which is a common problem with digital SLR cameras. 
The overall length of the lens does not change during focusing, ensuring convenient handling and ease of use. The new Sigma lens accepts both 1.4x and 2.0x EX Teleconverters to produce 420mm F4 and 600mm F5.6 Autofocus ultra telephoto optics.
The HSM (Hyper Sonic Motor) models provide fast, silent AF function as well as full- time manual focus override. A drop-in 46mm filter holder in the rear part of the lens barrel can be rotated to facilitate the use of filters, including a polarising filter, in situ. 
Simply adding an APO teleconverter (optional extra), means that this lens can be used as a 420mm F4 AF ultra-telephoto lens with a 1.4X EX teleconverter, or a 600mm F5.6 AF ultra-telephoto lens with a 2X teleconverter. 

Key Features
- Hyper Sonic Motor for quiet & smooth AF with fulltime manual focus override 
- Two ELD glass elements reduce chromatic aberration to a minimum and also ensure sharp, quality images of high contrast 
- Internal focusing with a non-rotating front 
- A drop-in 46mm filter holder in the rear part of the lens barrel can be rotated to facilitate the use of filters, including a polarizing filter 
- Removable tripod collar 
- Built in front protective filter 
- The rounded 9-blade diaphragm opening makes out-of-focus elements appear more natural