11 Fine-tuning your lens
When you purchase a lens you may need to calibrate it to match your camera. As explained in tip 6, this is because DSLRs use a separate autofocus sensor, unlike mirrorless cameras that use the main image sensor for AF, which is inherently more accurate. It’s easy to assume that you’ll instantly get great results as soon as you attach your lens onto your camera, however remember that lenses and cameras are made in different factories, and there are margins of error during the construction period that the manufacturers deem acceptable. Calibrating each lens to each camera body you use will give best results.
You can calibrate your lens at home with the help of a special chart (or if you don’t have one of these, simply use a test object and apply the same method). Start by putting your camera into aperture priority and opening the aperture to the widest setting. Mount onto a tripod and place your chart or object around 6ft away from your camera. Go to your camera’s lens calibration feature (on Nikon it’s Autofocus Fine Tune, Canon - Autofocus AF Microadjustment, and Sony - Auto Focus (AF) Micro Adjustment) and take a shot with the value set at 0. Then shoot in intervals of 5 from -20 to +20, and review the results on a computer screen to compare the sharpness of your main focal point. You then can tune finer once you know roughly what your setting needs to be. For example if +5 is the sharpest setting, take another series of shots from 0 to +10, and use whichever value gives best results.