I tested the new Sony 400mm & 600mm: Here is what you need to know

Buy the Sony 400mm f/4.5: Buy the Sony 600mm f/6.3: Sony's new 600mm f/6.3 and 400mm f/4.5 GM primes weigh less than a bag of sugar — but should you buy them instead of the 200-600mm zoom? I'm Tony Northrup, and I put Sony's two brand-new ultralight super-telephoto primes through real-world wildlife, birding, and portrait testing in New York City. Both weigh under 1kg (995g and 994g), both are G Master glass, and…