Sigma 150-500, Sigma 120-400, Canon 100-400, Sigma 50-500. Click here to enlarge.
Tele zooms are very popular lenses, both for professional and amateurs: they offer good reach at an affordable price, and they can be a good "lightweight alternative" for handheld shots, or for long trips where you can carry heavy big lenses.
In this test, I have compared the Canon 100-400 (a very old lens, announced in 1997, but still one of the best tele zoom on the market) with the mythical Sigma "Bigma" 50-500 and with the new Sigma 120-400 OS and 150-500 OS, two new interesting teles with both image stabilization and ultrasonic autofocus.
 
Specifications