Bests & Worsts Reviews from Amazon

This lens is amazing for the price. But it is not perfect. Looking backwards, the only comparable lenses are professional primes such as Canon/Nikon 500-600mm lenses. This lens gives you 80-90% of what those lenses bring. Older third-party superzooms are notably inferior. Looking forward, Sigma has a 150-600mm that provides clearly better IQ (how much better is debatable), but costs $900 more and is 2lbs heavier. The additional weight and bulk is a bigger concern for me since this lens at 4lbs already stretches my limits. This lens is great through 450mm and very good to 500-550mm. It's noticeably softer wide open at 600mm but sharpens up when stopped down to f/8 or f/9. The IQ at 600 is akin to having a very good 400mm with a 1.4x teleconverter attached. The Tamron is good enough at 600mm that I shoot 90-95% of my shots at that focal length. The biggest knock against it is the autofocus. It is slow to lock on and makes it difficult to shoot birds in flight. It is noticeably inferior to my Canon 70-300L, which is much quicker with greater accuracy. But the Canon only goes to 300mm. What it means is that I will need to improve my technique to get the keeper rate up. Regardless, I consider it a fair trade off because the images that are in focus are excellent and could not be obtained by lenses with shorter focal lengths.