A favorite for wildlife photography. I have gotten some great butterfly shots with this lens on my Sony A7R cameras.
Quoting the Tamron description:
“The 50-400mm F/4.5-6.3 Di III VC VXD (Model A067) is an unprecedented, nextlevel ultra-telephoto zoom lens with added versatility that starts at 50mm and delivers an 8x zoom ratio. With its wide 50mm starting focal length, full-body shots of subjects like wildlife can be captured in the surrounding environment. The generous and effective use of special lens elements, including XLD (eXtra Low Dispersion), LD (Low Dispersion) and Hybrid Aspherical lens elements, effectively delivers uncompromising high image quality throughout the entire 50-400mm zoom range. Along with its superb performance, the lens is just 183.4mm (7.2 in) long and weighs only 1,155g (40.7 oz). Offering about the same light weight and compact size as a conventional 100-400mm zoom, it’s easy to pack and comfortable to carry all day. Clearly, the TAMRON 50-400mm F4.5-6.3 is a brand-new kind of ultra-telephoto zoom lens that combines a 50mm standard focal length, outstanding image quality and highly nimble mobility—plus the sheer power of a 400mm telephoto! This one lens captures a lively world with all the clarity you desire and can transport you to exhilarating new photographic experiences.”
I certainly concur! In addition to wildlife photography I enjoy sniping with this lens, catching people from a distance when they are unaware that I am photographing them. Plus the wide end is great for landscape and street shots.
Here are some links to reviews by professionals:
Cameralabs
… and here are some sample images from my studio. Click on an image to see a full-screen photopost and image details