The Sony 70-400 SSM G lens is a professional grade telephoto zoom. Here, I show detailed photos of the lens and compare it to the Sigma 50-500 (also known as Bigma).
Both the 70-400 G and Sigma 50-500 zoomed to their extreme ends. If you include the lens hoods, they're both the same length... even though the Sigma's lens body is much bigger at 500mm. :)