From VFXPedia

Unsharp Mask [US]

Unsharp masking is a technique used to sharpen only the edges within an image. This tool is most often used to correct for blurring and loss of detail in low contrast images; for example, to extract useful detail from long exposure shots of far-away galaxies. This filter operation is performed by extracting a range of frequencies from the image and blurring them to reduce detail. The blurred result is then compared to the original images. Pixels with a significant difference between the original and the blurred image is likely to be an edge detail. The pixel is then brightened to enhance it.

Contents 1 Unsharp Mask [US] 1.1 Controls Tab 1.2 Tips for Unsharp Mask (edit)

Controls Tab

These checkboxes are used to select the channels affected by the image. Deselect one of the color channels to prevent the effect from being applied to that channel.

This is not the same as the RGBA checkboxes found under the common controls. The tool takes these controls into account before it processes, so deselecting a channel will cause the tool to skip that channel when processing, speeding up the rendering of the effect.

In contrast, the channel controls under the common controls tab are applied after the tool has processed.

When Lock X/Y is checked, both the horizontal and vertical sharpen amounts will be locked. Otherwise, separate amounts of glow may be applied to each axis of the image.

This control adjusts the size of blur filter applied to the extracted image. The higher this value, the more likely it is that pixels will be identified as detail.

The Gain control adjusts how much gain is applied to pixels identified as detail by the mask. Higher values will create a sharper image.

This range control determines the frequencies from the source image to be extracted. Raising low values will eliminate dark pixels from the comparison. Pixels above the high value will have the full effect of the gain applied.

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Tips for Unsharp Mask (edit)

EyeonTips:Manual/Tool Reference/Blur/Unsharp Mask