I'm looking for a new digital bridge camera to replace my Panasonic FZ200 (24× optical zoom, f/2.8). I take lots of bird photos & want a camera with more zoom. After much research, I don't understand how the different features (sensor size, aperture, etc.) Work together to produce a clear image at a long distance. For instance, the Panasonic FZ2500 is top rated, but has 20x optical zoom (f/2.8-4.5, 24mm-480mm lens). Would this camera take a better long distance photo than my FZ200? I see other cameras out there like Nikon CoolPix P1000 with a ling zoom, but it's not rated any where near the Panasonic. Could someone explain what features help to make a clear image at a long distance? Thanks.