Very new and still trying to sort out all the various settings available on my D5600. I've been using my Nikor 70-300 kit lens on wildlife at the local refuge with very mixed results. At 300 mm I've used a tripod, remote shutter release, high shutter speed(1/1000) and medium aperture(f5.6-f9) and the image seems sharp until I zoom or crop. Then it is just fuzzy enough to make the image unusable. Am I expecting too much from the lens or am I doing something stupid(very likely)? Any help would be appreciated.