This lens has a field of view equivalent to an 80-240mm lens on a full frame body. Traditional options in this range are 70-200mm lenses which have a field of view equivalent to a 112-480mm lens. This Sigma is a very nice lens but I found it a bit lacking for field sports back in the Fall. Where it excels, however, is indoor events where the range between 50mm and 70mm (80-112mm equivalent) can be quite useful and where the extreme long end of the 70-200mm is usually not needed. The optical stabilization also helps with slower shutter speeds which are sometimes necessary with indoor events.
So, I decided to use the Sigma for a flute choir concert yesterday. My kit was the Sigma lens, a Canon 7D body and a Canon EF-S 24mm f/2.8 pancake lens. Here are a few that show the range of the Sigma lens. For all the photos you may visit http://trulandphoto.zenfolio.com/cafc.
|50mm, f/2.8, 1/60 sec., ISO 1600|
|76mm, f/2.8, 1/60 sec., ISO 1600|
|118mm, f/2.8, 1/90 sec., ISO 1600|
|150mm, f/2.8, 1/90 sec., ISO 1600|
So, since this lens has been discontinued by Sigma I think I'll hang on to it for events like this. For outdoor sports, a non-IS Canon 70-200mm f/2.8L will do fine.
UPDATE: 5/4/15 - Well, I decided to put the lens back up for sale and it sold today on eBay for my asking price. My current plan is to use those proceeds, proceeds from other Sigma lans sales and the sale of one of my 7D bodies to purchase an EOS 6D body. Now that I've got the EF 70-200 f/2.8 zoom and EF 28mm f/1.8 prime lens I've got enough to get started back with a full frame body.