Having a lens with the correct focal length lens mounted can make the difference between getting a shot and getting nothing. In this case, I was shooting landscape with a wide angle lens when this California Condor flew over. I quickly pulled out my second camera with the 70-300 L mounted and was able to get the shot. In this case, I could have used much more focal length as the shown image is cropped. I could have used a slightly faster shutter speed as well. Hindsight is always perfect. Experience brings foresight closer to perfection.