An important function that allows the user to add apparent clarity via electronic means. Unsharp masking is considered the most sophisticated sharpening method because it sharpens without the undesirable graininess that appears with other sharpening methods.
A filter used to reduce noise while retaining most of the high frequency detail in an image. Unsharp masking is accomplished by subtracting a low-pass filtered version of an image from the original image.
A technique used to make scanned images sharper. The process of scanning an image can make the image appear soft; high-end DRUM SCANNERS perform unsharp masking automatically to create a sharper, crisper image. FLATBED SCANNERS usually do not perform unsharp masking. Image editing applications such as Adobe Photoshop can be used to unsharp mask an image. (The name "Unsharp Masking" comes from the pre-computer photographic process used to sharpen a blurry negative.)
a software feature that selectively sharpens a digital image in areas of high contrast whilst having little effect on area of solid colour. The effect is to increase the apparent detail and sharpness.
an artificial transformation that can make images appear more in focus by exaggerating transitions that have been dulled by scanning.
A function of image editing software that increases the overall contrast at the edges of density or color changes by exaggerating the differences. In the scanner or color manipulation work-station, the computer reads the digital signals to locate where the color changes occur and then adjusts the tones and colors to create a more sudden change. If carried to an extreme, the exaggeration can result in an outline effect between some colors. During photographic color correction procedures, an unsharp mask simultaneously compresses the tones and makes the corrections. In either case, unsharp masking, despite its name, globally increases the detail of an image.
A procedure for increasing the apparent detail of an image performed either by the input scanner or by computer processing.
An image enhancement technique using a high-frequency accentuating filter.
Used to sharpen edges in an image.
A prepress term describing a technique of adjusting dot size to make a halftone or separation appear sharper (in better focus) than the original photo or the first proof. Also referred to as edge enhancement and peaking.
((often abbreviated USM) Describes an image focusing process. The quality of the result depends on the characteristics of the algorithm used.
An image processing technique where a second image is created that is an out- of-focus (blurred, low-pass filtered) version of the original. The second image's pixel values are subtracted from the corresponding pixel values in the original image, enhancing detail in the image. Its use (and terminology) dates back to early photographic techniques.
A technique used by scanners and image editors to increase the sharpness of an image.
A process by which the apparent detail of an image is increased; generally accomplished by the input scanner or through computer manipulation.
Unsharp masking is an image manipulation technique now familiar to many users of digital image processing software, but it seems to have been first used in Germany in the 1930s as a way of increasing the accutance, or apparent sharpness, of photographic images. The "unsharp" of the name derives from the fact that the technique uses a blurred, or "unsharp", positive to create a "mask" of the original image. The unsharped mask is then combined with the negative, creating the illusion that the resulting image is sharper than the original.
