How to sharpen your image with the Unsharp Mask filter

There is no doubt that photography has gone digital. You may not realize it, but along with the advancements in digitalization also comes loss of sharpness with most images.

Fortunately, photographers and photo enthusiasts don't have to settle for dull images. You can sharpen images without getting gritty prints simply by using the Unsharp Mask Filter, a tool found in both Photoshop and Photoshop Elements.

Digital cameras produce images that contain a range of acutance or "softness." Higher acutance equals a sharper image. By using the Unsharp Mask Filter, which exaggerates the light-dark contrast between the edges of an object, you can control the acutance after the shot has been taken.

Why is sharpening so significant? It can reveal fine details that otherwise would never have been seen in the original, making images appear more crisp and clear. Examples of this include architectural details of a building, subtle facial features and more. As a rule of thumb, remember that every digital picture needs to be sharpened.

It is important to note that resolution and contrast, while both valuable, are very different. A high-resolution image cannot add sharpness. Resolution adds detail and sharpness distinguishes edges.

You use unsharp to make sharper? Huh?

Many users are often confused why something called an "unsharp mask" is used to sharpen images. Wikipedia has a good explanation:

The "unsharp" of the name derives from the fact that the technique uses a blurred, or "unsharp", positive to create a "mask" of the original image. The unsharped mask is then combined with the negative, creating the illusion that the resulting image is sharper than the original.

Let's see it in action

Let's start with the sample image, shown in Figure A.

To begin, you will want to sharpen each image to the size you would like it to print. For best printing, use 200 to 300 ppi resolution. In this example, we are using 240 ppi and are viewing the image at 100% in Photoshop.

In Photoshop or Photoshop Elements, go to Filter > Sharpen > Unsharp Mask.

In the magnifier preview window, move your curser over a part of the photo that has good contrast between dark and light areas of the image.

To ensure that you do not over contrast your image, use the Unsharp Mask moderately, as you can see in Figure B.

Move the Amount Slider to 100% or above until a white line or edge appears in the preview between the dark and light areas. Adjustment the Amount Slider back to just before you saw the white line or halo appear.

Keep the Radius Slider low at about 1, 2 or 3 to keep the contrast from becoming too much in the image.

The Threshold Slider is to prevent grainy textures from increasing during this process. This slider is usually adjusted by eye and kept at a low setting. In this case, 3 is the best setting to prevent the blur from going too far onto the faces in the preview window.

And there it is, increase perceived sharpness by increasing the contrast between the areas and objects in the image. To really appreciate it, click Figure C to take a look at full size image and look at the two samples side-by-side.

Another factor to keep in mind is if you are not using your own printer for output, consult your lab service to see if they have a sharpen feature within their printing process. If so, you will not want to sharpen your image, as double sharpening would not yield good results.

Jane Conner-ziser is considered one of the best retouching experts in the field, her clients include Canon, Art Leather Manufacturing Co, Marathon Press, Kodak, many of the nations largest professional color labs, and numerous studios of fine portrait and commercial photography. She is a featured trainer for Software Cinema who is a strategic partner of Adobe Systems focused on interactive learning for the digital imaging industry. For more information visit http://www.software-cinema.com.