You have already received excellent advice about long telephoto lenses. However, I thought a little information on the A lens mount adapter is important to pass on. If you buy one to use a long telephoto, you will lose image stabilization. This loss will make handheld photography of the long lens difficult and you will be limited to tripod mounting the lens. This may not be as much of a handicap as you might think. Once you start working with lenses whose focal length is 300 mm or greater, their weight makes handholding difficult. Aiming and composing at these long telephotos can be a daunting task. You may find using a tripod makes lens handling a much easier proposition. Having said that, the advantage of using the 70-400 mm Sony lens (a favorite of mine) on the a77 is that you can handhold it for photography. For this reason, I still use the a77 with this lens, even though I have a NEX-7 and the Sony A mount adapter for mounting the lens on that camera.