The Sharpest Knife in the Imaging Drawer

Today’s Post by Joe Farace

One of the biggest advantages that digital imaging has over traditional photography is the ability to sharpen your images.

Many image editing program, including Adobe Photoshop, contain a Sharpen command that works by raising the contrast of adjacent pixels but sometimes increased sharpness occurs at the expense of overall contrast. Some photographs can handle additional contrast before loosing highlight detail, while others can’t. A better bet is to use the unlikely named and wonderfully practical Unsharp Mask (Filter > Sharpen > Unsharp Mask) command found in Photoshop and other image-enhancement software to sharpen a photograph.

Photoshop’s Unsharp Mask’s dialog box provides three sliders that let you control sharpness. The Amount slider displays the percentage of sharpening that will be applied to your photograph. Don’t be afraid to apply more than 100 percent to high-resolution files but lower resolution images will fall apart fast if higher amounts are used. The Radius slider determines the number of pixels surrounding the edge pixels for sharpening. Lower values sharpen edge pixels, while higher values sharpen a wider range. The Threshold slider determines how different that sharpened pixels must be from their surrounding area in order to be considered edge pixels. The default value of zero sharpens all pixels in the image.

Tip: Here’s a useful way of dealing with color fringing that can occurs when applying Unsharp Mask. After sharpening the image file, go to the Fade command (Edit > Fade Unsharp Mask) that appears only after any filter is applied. Don’t change the Opacity setting,leave it at 100%, but select Luminosity from the pop-up menu. Any color artifacts should be gone or if not, at least, minimized.

 

Photoshop’s Smart Sharpen (Filter > Sharpen > Smart Sharpen.) has a dialog box similar to Unsharp Mask but includes an advanced Mode featuring three tabs, including Shadow and Highlight. The first two sliders are Amount and Radius and act as they did in Unsharp Mask but in place of Threshold, there’s a pop-up menu that lets you control sharpness for a specific kind of lack-of-sharpness problem including Gaussian, Motion, and Lens Blur.

 

 

Along with photographer Barry Staver, I’m co-author of Better Available Light Digital Photography that’s available from Amazon for $21.88 prices with used copies selling at giveaway prices—less than four bucks, as I write this.