Sorry if this has already been covered but I'm a bit of a virgin with DSLR's. I have a Nikon D7200 DX Body with a couple of kit lenses. i have recently aquired a Nikkor AF-S 70-300mm 1:4.5-5.6 ED IF which is an FX lens. All the info suggests it should perform as a 450mm on my DX body but ... The focal length and recorded image look exactly the same as my 300mm DX kit lens. Am I missing something ?
Lenses are always named with their actual focal lengths and not 35mm equivalent length. So both your dx and fx 300mm lens has the same focal length. The only difference is that the dx-only lenses are made smaller to save money. So on a dx body , using a dx or fx lens of the same focal length makes no difference. So your 300mm lens + dx body gives the same angle of view as a 450mm lens + a fx body And actually lenses are the same . The change in focal length is when you use the same lens on a fx and dx body. A 300mm fx lens give 300mm angle of view on an fx body. The same lens give 450mm angle of view when use on a dx body