Given the value from {@see #ExifTagKey.FOCAL_PLANE_RESOLUTION_UNIT} or {@see #ExifTagKey.RESOLUTION_UNIT} this method will return the corresponding value in millimeters
Return
resolution in millimeters
Parameters
resolution
{@see #ExifTagKey.FOCAL_PLANE_RESOLUTION_UNIT} or {@see #ExifTagKey.RESOLUTION_UNIT}