Sharpening Scans that Appear Blurred

Image editing applications such as Adobe Photoshop include a wide variety of different filters than can be applied to help improve the quality of any image, including scanned ones. One popular technique used to help minimize the impact of issues such as moiré patterns is to scan the image at double the resolution required with the descreen filter on, then resize the image to one-half of the current size, and finally apply a common filter known as the Unsharp Mask. Although its name might not suggest it, the Unsharp Mask is a filter used to restore the sharpness in an image, some of which might be lost after sampling an image to a smaller size.
Filters.bmp: Image-editing programs like Adobe Photoshop include a variety of different filters that can be used to improve scan quality.

If you’ve already scanned an image without the descreen option and no longer have the original hardcopy, all is not lost. Another popular way to remove moiré patterns is to slightly blur the image, causing the dot or crosshatch pattern to blend more naturally. Applications like Photoshop include a variety of blur-related filters on the Filter menu, but one of the most popular is known as the Gaussian Blur. Try using this filter on the full-sized image with the moiré pattern, and then resize the image and apply the Unsharp Mask filter to complete the process.

Author: Dan DiNicolo

Dan DiNicolo is a freelance author, consultant, trainer, and the managing editor of He is the author of the CCNA Study Guide found on this site, as well as many books including the PC Magazine titles Windows XP Security Solutions and Windows Vista Security Solutions. Click here to contact Dan.