Basic Sharpening

Sharpening is normally the last thing you do before saving a file. There are many ways to sharpen an image in Photoshop. This tutorial describes the main sharpening method using the Photoshop Unsharp mask filter and includes some sample settings and describes when you might use them.

Step 1
To help you follow along with this tutorial the image used is available here. You can try the steps with this image first, then use one of your own, or open one of your own images now to work on. The most important thing to remember when working on sharpening is to view the image at 100%. To ensure you are viewing at 100% after opening the image either: double-click the Zoom tool or right-click on the image and select Actual Pixels. You will see the image title bar showing 100%.

Step 2
Under the Photoshop Filter menu, select Sharpen -> Unsharp Mask... This filter combines the image with a blurred copy of the original to produce the sharpened version.

Step 3
The Unsharp Mask dialog box will appear as shown below. Your dialog values may be different as this dialog remembers the last used settings.

The three sliders on this dialog have the following effect:

• Amount (%) - Determines the amount of sharpening.
• Radius (pixels) - Specifies how many pixels away from an edge the sharpening will impact.
• Threshold (levels) - Defines the intensity of the sharpening with a lower number meaning a more intense sharpening. Basically, this specifies how different a pixel must be from its surrounding pixels to be considered an edge and not just another pixel in a continuous color or area.

This dialog has a few additional capabilities that you will find useful.

• +/- Buttons - The +/- buttons immediately under the dialog image area can be used to zoom in and out on the dialog image to check your sharpening settings at different magnifications. You will normally want to leave this at 100% so you see actual pixel changes.
• Preview Checkbox - The Preview checkbox allows you to enable or disable the preview of your sharpening settings as applied to the image in the background. You can disable this for large images to speed things up.
• Dialog Image - Most useful is the dialog image itself. When you move your mouse over the image it is displayed as a hand. Left-click and drag the hand to re-position the window onto the image to get the most useful content visible. Left-clicking the image will temporarily disable the sharpening settings to view the original image (unsharpened). Try some settings then click and release on the dialog image to view the effect of these settings.

What values should I use? Click OK with the values shown in the dialog and compare the difference between unsharpened and sharpened images below.

Before

After

The effect above is oversharpened. What does oversharpened mean? Look at the area in the right hand image directly adjacent to the black bars behind the driver. They have developed a white border or halo. How do we avoid this? We can try using different more subtle settings in our Unsharp mask dialog.

Suggested Unsharp Mask Settings

A second sample file is used for these examples. Open the file and apply the settings below.

Original Sample

Soft Sharpening
(Amount 150%, Radius 1, Threshold 10)
e.g. People, Foliage, etc.

Portrait Sharpening
(Amount 75%, Radius 2, Threshold 3)
e.g. Faces

Note: Click on the images above to open the full size image.

To continue suggested ranges of settings and their uses see the following Unsharp mask settings applied to a third sample image.

Original Sample

Moderate Sharpening
(Amount 200-230%, Radius 0.5, Threshold 0)
e.g. Landscapes, images with clean lines, etc.

Maximum Sharpening
(Amount 60-75%, Radius 4, Threshold 3)
e.g. Original not tack sharp, buildings, image contains lots of edges, etc.

Generic Sharpening
(Amount 80-90%, Radius 1, Threshold 4)
e.g. all-purpose

Web Sharpening
(Amount 200-400%, Radius 0.3, Threshold 0)
e.g. 72dpi web graphics

Alternatively, we can use different sharpening techniques. We will cover some of those techniques in upcoming lessons, including Lab Sharpening and Sharpening Edges.