Hello, I have a Nikon Z7 (I love it) and use a Nikkor 200 - 500 lens with an FTZ converter, as the lens is a F mount. The rig is very heavy, and the converter slows my frame rate. So I'm considering getting a prime 400mm, since almost everything I shoot is at 500. Question is, will the better image quality enable me to crop more, and reach farther before the edges start getting blurry? Also, is there generally better AF performance? My full frame sensor is 45 mp, and I usually shoot as wide open as lighting will allow. Thanks for any input!