Embodiments of the invention provide a technique to sharpen luminance data associated with each pixel of a digital image without introducing certain sharpening artifacts. An alpha mask is generated based on first, second, and third alpha submasks that indicate how strongly overshoot, color fringe, and dark regions, respectively, are detected at each pixel location. The alpha mask is used to combine luminance data derived from the digital image with sharpened luminance data that is generated by applying a sharpening filter to the luminance data.