Web Design with HTML and CSS

84

Applying the Unsharp Mask fi lter to an image

Web Design with HTML and CSS Digital Classroom

Applying the Unsharp Mask fi lter to an image

We strongly recommend that you sharpen an image after you resize an it Photoshop because

it can become blurry. The Unsharp Mask fi lter is a great tool for sharpening images. The

following fi gure shows the image before and after you apply the fi lter. The Unsharp Mask

feature sharpens the image based on levels of contrast, while keeping the areas that don’t have

contrasting pixels smooth.

The image before (left) and after (right) you apply unsharp masking.

Follow these steps to apply the Unsharp Mask fi lter:

1 Choose View > Actual Pixels or double-click the Zoom tool ( ).

When you’re using a fi lter, you should view your image at its actual size to see the results

more clearly.

2 Choose Filter > Sharpen > Unsharp Mask.

The Unsharp Mask dialog box displays three options:

• Amount: The Amount value ranges from 0 to 500. The amount you choose depends
  upon the subject matter. For example, you can sharpen a car or appliance at 300
  or 400, but with a portrait, every wrinkle, mole, or hair will become more defi ned.
  If you are unsure about the value to use, start with 150 and gradually increase the
  amount until you fi nd a value that looks good.


• Radius: The Unsharp Mask fi lter creates a halo around the areas that have enough
  contrast to be considered an edge. For print images, you can use a value between
  1 and 2, but if you’re creating a billboard or poster, increase the size.


• Threshold: The Threshold value is the most important one in the Unsharp Mask
  dialog box because it determines the parts of the image that should be sharpened. This
  value can range from 0 to 255. Apply too much, and no sharpening appears; apply too
  little, and the image becomes grainy. For example, if you leave it at zero, noise appears
  throughout the image, much like the grain you see in high-speed fi lm. A value of 10
  causes the fi lter to apply when the pixels are ten shades or more away from each other.
  Start with a value of 10, and gradually increase it until you fi nd a value that works well.