I just spent my morning photographing some nesting burrowing owls that live a few miles from my house. Love watching these owls, and couldn’t stop laughing when an owl landed on top of a prairie dog and ‘pinched’ it as the prairie dog got too close to the owl burrow. Hilarious! As usual for wildlife I was shooting a D850/grip at 9 FPS with my 600mm F4. But I had noticed a week ago some of my images seemed unsharp, even when I was on a tripod shooting at 1/8000. I always turn off my VR at this speed, and generally shoot wide open. On a high resolution 45MP camera, with a 600mm lens at 30 feet from my subject, shooting at F4, I have around a 1.5 inches of depth of field. If your focus is off even a 1/4 inch, you will notice it. To my eye, my lens was focusing just slightly in front of my subject. Time to calibrate my 600mm.
Before you start to worry about calibrating your lens, just know this applies to super telephotos shooting wide open like F4. Cree(my wife) shoots a 500mm F5.6 PF on a D850 with no calibration…it is absolutely tack sharp. So calibration is more appropriate for super teles at F4 or F2.8. If your wide open aperture is 5.6 on super zoom like the 200-500mm, you probably won’t have to worry about a thing.
Calibrating your lens has become easy, and something you can do in a few minutes at home. First, see if your camera has a AF Fine-Tune option in the Set Up menu. The D850 does, and this is how you adjust where the lens focuses. Plus settings will move the autofocus forward. Minus settings will move it back. Next, I pulled out my handy, inexpensive Vello calibration target. This target has a bullseye and a ruler beside it. Set this up about 30 feet (or the distance you shoot at a lot) and make sure both your lens and the chart are level. Then focus on the target and take a shot. Zoom in and look at the zero mark on the ruler. The zero should be sharp. If it is not, then you need to calibrate the focus backward or forward until the zero is sharp when you take a photo. It is that simple.
Not something that every photographer will be interested in, but if you shoot long wide glass, and your images look a little soft, consider calibrating you lens using this handy tool.