Sharpening Using Unsharp Mask

I KNOW a lot of photographers who use Photoshop’s “unsharp mask” feature to sharpen their images, but only a few understand why this is called such. In most workshops, the trainer would just give you the magic formula of amount, radius and threshold and a few explanations. I wouldn’t blame them for not expounding on this topic; it’s quite mind-boggling, especially for beginners.

When do you apply sharpening? Can sharpening fix blurred shots?

When shooting in raw format, the camera records the data as is. No sharpening and other auto correction is applied. Unlike shooting in JPEG format, the file rendered is applied with sharpening, auto contrast, auto color and the rest. Raw files natively require sharpening since no other in-camera post processing is applied. This is a given nature of most of digital cameras due to the anti-aliasing filter and the bayer type of design of the sensor. When shooting in JPEG format, sharpening is already performed but for raw files, it’s definitely a must to sharpen.

Blurred shots due to optical focusing can be salvaged by sharpening, but only to a small degree. Quite frankly, this is only done when the option to reshoot is not feasible. We have to understand that sharpening in post-processing is a very much different approach compared to optical methods.

In post sharpening, Photoshop or other editing applications will try to find the edges of your image and apply contrast to those edges.

Unsharp mask is a technique developed and used in darkroom printing. Photographers call it custom lab. This was their version of Photoshop during the olden days. The same technique is applied when you choose Unsharp mask under filters in Photoshop. A blurred image is generated using gaussian blur to find the edges of the image. When blurring, the image actually expands, and when it is placed on top of the original image, the edges are then revealed.

When the edges are found, the “amount” slider in the “unsharp mask” dialog box dictates the degree of contrast to be applied on the edge.

Contrast will darken the dark part and brighten the bright part of the edge hence creating a stronger edge line. The “radius” slider dictates the number of pixel where contrast will be applied.

The higher the radius, the thicker the edge line becomes.

The third slider, “threshold,” lets you decide the coverage of edge to be sharpened.

The higher the value, the more strict it becomes. Skin pores are considered a weak edge and the more you increase the “threshold”, the more the weak edges are disregarded. By increasing the levels to about four (4), the skin is excluded from sharpening, which is a good thing.

Every image is different and therefore will require a different set of slider combinations. It takes practice and experimentation to master the art of sharpening. Keep on shooting, everyone!

And lest I forget, rest in peace Master Lito Chiu Inso. Thank you for the inspiration and the beautiful memories you left us. The entire photography community salutes you!

(photography@grp.ph / www.grp.ph)