Sharpening an image

Sharpening is an image-manipulation technique for making the outlines of a digital image look more distinct. Sharpening increases the contrast between edge pixels and emphasizes the transition between dark and light areas. Sharpening increases local contrast and brings out fine detail. There is no strict formula for correctly sharpening all images. Too little sharpening can make for a soft image, but over-sharpening adds halos, artifacts, and noise.

To sharpen an image, display it in the Sharpness Editor:

In Grid View, click the Edit rollover button and choose Sharpen.
Open it in the Browse Panel in Detail view and select the Sharpen button .

Choose commands and click the Save button.

Sharpening

Select the Sharpening menu and choose an option:

None

Disables sharpening.

Sharpen

Applies a basic sharpening filter. This filter can compensate for blurriness.

Unsharp Mask

Choose these options to fine-tune sharpening:

Amount: Controls the amount of contrast applied to edge pixels. The default is 0.0. For high-resolution images, you can increase it to as high as 5.0. Think of Amount as a measure of filter intensity.
Radius: Determines the number of pixels surrounding the edge pixels that affect the sharpening. For high-resolution images, enter from 1 through 2. A low value sharpens only the edge pixels. A high value sharpens a wider band of pixels. The correct value depends on the size of the image.
Threshold: Determines the range of contrast to ignore when the unsharp mask filter is applied. This option determines how different the sharpened pixels must be from the surrounding area before they are considered edge pixels and are sharpened. To avoid introducing noise, experiment with values between .02 and 0.2. The default value of 0 sharpens all pixels in the image.
Apply To: Choose Each Color to apply sharpening separately to each color component; choose Brightness to apply to sharpening to image brightness areas.

Resampling

Select the Resampling menu and choose an option. These options sharpen the image when it is downsampled:

None: Turns off resampling.
Bilinear: The fastest resampling method; some aliasing artifacts are noticeable.
Bicubic: Increases CPU usage on the Image Server, but yields sharper images with less noticeable aliasing artifacts.
Sharpen2: May produce slightly sharper results than the Bicubic option, but at even higher CPU cost on the Image Server.
Trilinear: Uses both higher and lower resolutions if available; recommended only when aliasing is an issue. This method reduces JPEG size due to reduced high-frequency data.

JPG Quality

The JPG Quality options control the JPG compression level:

JPG Quality: Select this option if you want to control compression levels and chrominance downsampling.
Slider: Determines the JPG compression level. This setting affects both file size and image quality. The JPG quality scale is 1–100.
Enable JPG Chrominance Downsampling: Because the eye is less sensitive to high-frequency color information than high-frequency luminance, JPEG images divide image information into luminance and color components. When a JPEG image is compressed, the luminance component is left at full resolution, while the color components are downsampled by averaging together groups of pixels. Downsampling reduces the data volume by one half or one third with almost no impact on perceived quality. Downsampling is not applicable to grayscale images. This technique reduces the amount of compression useful for images with high contrast (for example, images with overlaid text).