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Sharpening Images

Unsharp Mask

This is a powerful tool and unlike it’s name suggests, will help to sharpen a blurry image in specific areas. If for example, you have rotated an image or changed its dimensions or resolution it may blur due to the ‘interpolation’ that Photoshop applies. This may be alleviated by applying the Unsharp Mask

From the Filter drop down menu at the top of the screen, select Sharpen / Unsharp Mask.

A pop up box will appear.

The amount of sharpening must be entered. We suggest a figure of 96 for natural pictures.

The Threshold may be left at 0

Clicking / Unclicking the Preview option allows you see the effect.

Enter a Radius; we suggest a value less than 1.

Amount:
This value controls the amount of sharpening applied to the edges. Values between 1 – 500 may be entered. If a high value is used images become ‘pixalated’ and look unnatural. Values between 50 – 250% will render the most moderate results and thus more natural images.

Radius:
Controls the depth of pixels along the high contrast edges. Values of 2 or less produce the most acceptable sharpening. We suggest a value 0f 0.8 but experiment with your own image!

Threshold:
Sets the level for the minimum amount of contrast between pixels an area must have before it will be modified. The Threshold value is the difference between two adjacent pixels- as measured in brightness levels – that must occur for Photoshop to recognise them as an edge.

High Threshold values limit changes to areas where there is a high degree of colour difference. Use low values to apply the filter more evenly throughout the image.
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