What megapixels do you have on your camera? I was hoping that if the megapixels was higher than 20 I could end up just cropping in to get the same magnification?

What I have noticed is that with the 400 zoom (which is 800mm full frame equivalent) I have to zoom out most of the time to 350 or 300mm sometimes even lower when its a bird in flight because it is near impossible to follow otherwise. So the full frame 600mm is perfect in my opinion. Other thing is at 400mm the image quality is very bad anyway.