AST Works Folding Card Lens Focus Calibration Alignment AF Micro Adjustment Ruler Chart Item name: folding card lens focus calibration alignment af micro adjustment ruler chart features: pact ruler allows you to determine if your lens is auto-focusing accurately as it should. It is an essential tool that is particularly useful when shooting with a shallow depth of field, where focusing should ideally be "spot on".You can use this ruler to determine how "off" the focusing is for a particular camera /bination and, on supported cameras, adjust the camera's auto-focus settings to resolve this on nikon cameras, this feature is known as "af fine tune".On canon and sony cameras, it's known as "af micro adjustment".Please refer to your camera's instructions manual to see if this feature is present. How to use: set up the ruler. Ensure both the camera and ruler are level, exactly perpendicular and at the same height. It is best to mount the camera on a tripod to do this. Set the lens to the widest aperture to obtain the shallowest depth of field. This will make it easier to determine if your lens is focusing accurately. Auto-focus on the crosshair at the center of the ruler, then take a photo. Inspect the photo to see if focusing is accurate. It ismended that you do this onputer since you will be able to see better on a bigger screen. If focusing is accurate, the '0' on the ruler should be the sharpest point on the image and the other numbers get blurrier as you move away from the 0. If any number above the 0 is clearer, then your lens is backfocusing. Otherwise, if any number below the 0 is clearer, then your lens is front focusing. In either case, you would have to set the auto-focus micro-adjustment parameters on your camera body until you are able to obtain a picture that is sharpest at the '0' on the ruler. Specification: size: 19x12.3cm/7.48x4.84''(approx) quantity: 1 pc warm prompt: 1. As different measuring methods, it will occur 1-3 cm deviation about the items, please ensure that it is okay for you before