I enjoy photographing wildlife and I'm always trying to get more detail. I've got a Canon XTi with a 100-400 L series lens, I've used apeture priority most, but also shutter priority, manual and the camera's auto settings. Some handheld and some tripod, but still trying to get more detail/sharpness. I've wondered at times if the camera has an issue, I've cosidered upgrading to another camera, or if it's just me. Any suggestions?