really close distance ,depend what I want to catch like shot ,buzzards in action shots 20 meters even less,for small birds closer distance .Very often using 400 2.8 @2.8 when light is poor or try to separate bird from backgroud
Ok brilliant, thank you. As I only have the 300mm f4 IS atm. Would you say it'd be worth getting a 2x extender because i'm thinking would f8 be too slow of an aperture for something that needs such fast focusing? Plus at f8 i'd need to be fairly close to even get a shallow depth of field.. ?