unsharp masking

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unsharp masking

(un-sharp ) A process for amplifying fine detail in the image on a photographic plate. A positive contact copy is made through the glass on low-contrast film. The copy is blurred, containing only the large-scale features of the original image; this is the unsharp mask. When placed in contact with the back of the plate, it effectively cancels out the large-scale features, revealing the fine detail on the plate.
Collins Dictionary of Astronomy © Market House Books Ltd, 2006
References in periodicals archive ?
CAD for Detection of Brain Tumor Using the Symmetry Contribution from MR Image Applying Unsharp Mask Filter.
In addition to the method mentioned above, the use of an unsharp mask in conjunction with a highboost filter for the sharpening of images is also widely used in printing and publishing industry [1].
The resulting image was processed by applying an unsharp mask to bring out fine details in the tail.
The sharpening techniques utilized are - Low Pass filter (utilized by NASA), UnSharp Mask, and Threshold.
Today we use "unsharp mask," a technique pioneered by astro-photographers, whereby a blurred negative is sandwiched with a positive to enhance edge details in images of distant galaxies.
I used unsharp mask at strength = 100%, with distance = 1.5 pixels, and threshold of 3 levels.
An unsharp mask filter was then applied in Photoshop to optimize sharpness for print, and each image was saved in TIFF format.
While most astrophotographers have success improving their images using standard sharpening tools like the popular Unsharp Mask tool in Adobe Photoshop, they often report that deconvolution either didn't work or made their images appear worse.
Besides the so-called toning of the image to bring the contrast into a proper range for reproduction and, if necessary, opening a shadow or two, the users of the new camera are using an unsharp mask in Photoshop's lightness channel to sharpen images.
You can further enhance it using Astroart's Unsharp Mask filter (Filters > Unsharp mask) or by increasing contrast before saving the final results.
Other approaches include sharpening by channel, whereby the unsharp mask is applied only to a few selected RGB or CMYK channels; applying local sharpening using layer masks; or using blurs to isolate the areas requiring sharpening.