I had been following this buck for two hours. I already had many in-the-woods pictures of it including some bedded images. But when it moved into the edge of a clearing with great lighting and a great background, I was especially thankful for the Canon EF 200-400mm f/4 L IS USM Lens I had mounted. This lens allowed me to quickly shooting a variety of subject framing with extremely good resulting image quality.
Also note the use of a monopod. Handholding this lens for most of that two hour period of time would not have been practical for me. And a tripod would have taken too long to adjust to get this shot. Using a monopod gives me much enough stability for the somewhat fast shutter speed necessary to capture the constantly moving deer. And the 1/400 shutter speed was not always fast enough for the latter.