It requires a tripod, two standard rulers, a pen or pencil, and a piece of the whiteboard. You can also purchase a calibration target online.

The first thing is to put the whiteboard on a low flat table.

Draw a very thin clear straight line on the whiteboard where the camera will have a specific point to focus on.

Align the two rulers along that line in a particular point, about 20 centimeters; following this you make sure that nothing moves either your board, ruler, or your camera.

With your camera facing the whiteboard below, select your central focus point and place it on the center of that line; recommended shooting into the full aperture, for the shallowest depth of field possible.

Manually focus your camera temporarily, defocusing it to the line, then set your camera on autofocus so that it can try to focus on the line.

When the camera is focused on the line, place the two rulers into the line but be careful not to move anything on the table

The position of the ruler is into 20-centimeter mark, exactly on that line then take a shot and examine the result

Try to zoom in on the picture taken and notice if the result of the image is sharp on the center which is in 20 or otherwise. If the result goes far from beyond the distance on the actual mark we focused on we proceed to the next step.

We go to calibration, in the Menu of your camera find AF(autofocus)->Adjustment select adjust by lens and press info to register(this is for the particular camera).

Under the ->AFadjustment, a graph will appear which has a mountain and camera symbol in between the graph with +20(going mountain symbol) to -20(going camera symbol) figure. Then you will just need to adjust based on the result of your image taken before either you’re going to the distance (mountain symbol) or going to the camera symbol.

If your image result earlier goes upward beyond the actual mark, you just need to adjust it near to the camera symbol (-20) and if it goes down from the actual mark, adjust going to the mountain symbol (+20), then just press OK from your camera.

Then take a shot again, examine the result. Just repeat the process until you get the best result.