An image data processing method for sharpening a captured image; the method defines a first transformation equation to change the pixel values of a defocused image into a focused image using the coordinates of the defocused image and the focused image as arguments, calculates a DetailedFocus function from the optimal solution of the first transformation equation by giving the pixel values of the focused image and the defocused image as educational data, extracts a predetermined number of important points on the DetailedFocus function, defines a second transformation equation to change the pixel values of the important points of a defocused image into a focused image using the coordinates of the defocused image and the focused image as arguments, calculates a SmartFocus function from the second transformation equation, and produces a focused image from a defocused image using the SmartFocus function.