Sharpen filter in image processing improves spatial resolution by enhancing object boundaries but at the cost of image noise:
        i) Highlight fine detail.
        ii) Enhance detail that has been blurred.

There are various methods of sharpen filtering depending on applications:
        i) High pass filtering.
        ii) High boost filtering.
        iii) Derivative filtering.

This filter is used mainly to increase the brightness at edges and boundaries. Its kernel size can be 3 x 3, 5 x 5 or 7 x 7 as shown in Figure 1371a.

(a)	(b)	(c)

Figure 1371a. Kernel size: (a) 3 x 3, (b) 5 x 5, and (c) 7 x 7.

In Gatan Digital Micrograph, sharpen filtering function is performed with kernel size 3 x 3 (Figure 1371a (a)) by the following steps:
        i) Open or select the image you want to sharpen.
        ii) Choose SHARPEN from the SPATIAL FILTER submenu under the PROCESS menu.
        iii) A new, sharpen-filtered image will be created.

In Photoshop, sharpen filtering function can also be performed (e.g. Figure 1371b) by the following steps:
        i) Open or select the image you want to sharpen.
        ii) Choose SHARPEN from the SHARPEN submenu under the FILTER menu.
        iii) The image is then sharpened.

(a)	(b)