If you want the minimum focal length for birding, top quality optics, are on a budget and Image Quality is priority # 1, the Canon 400mm 5.6L may be the lens you\'re looking for. I didn\'t like the push/pull of the Canon 100-400 and at 400mm the IQ wasn\'t as good as I\'d seen from the prime so I opted for the 400mm. I made my decisions from borrowed equipment.
Once I purchased the 400, I tried handholding it which produced lots more OOF shots than sharp ones. The Tripod solved that. I also found that with ext. tubes it served pretty dang good as a \"monster macro\". The USM focusing is smoking fast! The retracting hood is wonderful, I just wish it would lock backwards as it does forwards. Keep in mind that 400mm is the minimum focal length (IMO) for decent birding. More often than not, it still comes up short for me. Unfortunately going up to the 500mm makes a BIG dent in the wallet. If you buy this lens, you won\'t be dissappointed.
Once I purchased the 400, I tried handholding it which produced lots more OOF shots than sharp ones. The Tripod solved that. I also found that with ext. tubes it served pretty dang good as a \"monster macro\". The USM focusing is smoking fast! The retracting hood is wonderful, I just wish it would lock backwards as it does forwards. Keep in mind that 400mm is the minimum focal length (IMO) for decent birding. More often than not, it still comes up short for me. Unfortunately going up to the 500mm makes a BIG dent in the wallet. If you buy this lens, you won\'t be dissappointed.