JJC ACA-01 Autofocus Calibration Aid is a focus test chart, which is specially designed for cameras with “AF Fine Tune” or ” AF Micro Adjustment” function. It allows you to test the autofocus performance of your camera and helps you fine-tune the autofocus function of your camera and lens. The Autofocus Calibration Aid comes with a built-in bubble level for keeping itself on the level. It also features a 1/4″-20 tripod socket for mounting it on a tripod. JJC ACA-01 test chart will become a good partner for you to test the autofocus performance and fine-tune the autofocus function of your camera and lens.