As I wrote before in my photoshop tutorial, sharpening your photos is one of the more important things you can do when correcting photos for publication. However, to most effectively sharpen your photos, it helps to understand what is going on behind the scenes and how this changes your photos. To that end, this journal entry will discuss how to effectively sharpen your photos.

When looking to sharpen your photos, the name "unsharp mask" may seem a bit of a misnomer at first glance. You want to sharpen your work, not unsharpen or soften it. But reading it again, what you are really getting is an unsharpened mask, where the mask is applied to the original to make a sharp photo. This is accomplished in programs such as Photoshop by taking a copy of the image to which you are applying the unsharp mask and applying a Gaussian blur to it. The differences between the two is compared and applied to each other. The resulting image is therefore sharpened.

To fully understand how unsharp mask works, allow me to show you how you can manually apply an unsharpened mask to your photo. First, open your photo, such as the one we have here, into Photoshop.



With your picture open, which is presumably a jpeg with only a background layer, you should duplicate the background layer. You can do this by going to the layer window and right clicking on the background layer and selecting Duplicate Layer... Now you'll have two layers that look exactly the same.

The next step is to select the new layer and apply the Gaussian blur. The Gaussian blur is a filter built into Photoshop, and it is located under the Filters menu, in the Blur subcategory. The radius is simply the degree to which the blur will be applied, so that for every pixel that is blurred, the blur will be pushed out this many pixels. Once the Gaussian blur is applied, you'll have a picture that looks kind of like this.



The next step is to invert your photo. This can be done by going to the Image menu, and selecting the Adjustments subcategory and choosing Invert. You'll end up with something like this.



The final step in our manual unsharp mask example is to blend the two layers. Here you are blending the original layer, and the blurred and inverted layer. To do this, right click on the blurred and inverted layer and select Blending Options. From there you can select the Blend Mode from things like Normal, and Dissolve. You want to select Overlay. The Opacity can be changed from here, too, and this will affect the amount of the sharpening, similar to the amount percentage on the unsharp mask dialog. You'll end up with something like this.



Hopefully you can see that this looks exactly like your photo would look had you simply gone to the unsharp mask filter yourself. However, hopefully you can also see how the unsharp mask tool works so you can apply it more effectively.

But wait! There are more options from which you can choose. For those of you who like options, we have the High Pass filter.

So you start out with the same photo as shown above. After you've applied your levels layer, and your curves layer, and your color balance layer, etcetera and etcetera, you can create another copy of your original background layer as described above. Once you've created the new copy of the original background layer, you want to apply the high pass filter to it by going to the Fitler menu and selecting the Other subcategory and choosing High Pass.... A radius of 10 is a good default and should be left that way. You'll end up with a layer that looks something like this.



Next, as we did before, we are going to blend this layer in so that the sharpening can be applied. To do this, right click on the high pass layer and select Blending Options. From there you can select the Blend Mode from things like Normal, and Dissolve. You want to select Hard Light. The Opacity can be changed from here, too, and this will affect the amount percentage of the sharpening. Ideally, this should be between 30% and 70%. You'll end up with something like this.



But wait! There's more! What do all those options on the unsharp mask dialog mean anyway? To illustrate the three options present on the unsharp mask dialog, we're going to use this really boring picture that consists of only two colors.



The first option on the unsharp mask dialog is the amount. This is the most influential option in the dialog, and it will be the one you usually adjust. Most basically, it changes the amount of sharpening applied. Looking at the above example using the Gaussian blur, it is the same as changing the percentage of the blend between the blurred layer and the original layer. The greater the percentage, the more sharpening is applied. But be careful, too much sharpening is worse than not enough, and can lead to interesting lines coming forward in your photo.

Below are examples of three levels of sharpening applied to the above original, blown up 300%. The first one is 50% unsharp mask, the second one is 100% unsharp mask, and the last is 200% unsharp mask. You can see clearly the way that the photo is affected by the unsharp mask tool.





As more sharpening is applied, more pixels are affected and the line directly between the two colors becomes lighter. This means that as more sharpening is applied, there will be greater accents on contrasting lines and the photo will pop more. But do not over do it, or things that aren't lines will begin to pop in the photo, as well.

The next option you can change is the radius. The radius affects how many pixels away from each contrasting edge is affected. The greater the radius, the greater the effect. Usually a radius between 0.5 and 1.5 is preferred, so as to not exaggerate lines and adversely affect areas of the photo. To understand why, let's look at what happens when we select different radii. The photos above all used a radius of 1. The first photo below used a radius of 2, the second a radius of 5, and the third a radius of 10.





As you can see, a smaller radius is clearly preferred so as to not accent contrasting lines across a greater area of the photo than necessary.

The final option on the unsharp mask dialog is the threshold. The threshold is merely the point at which changes won't be recognized. This is not an important option and should not be changed off of 0.

So in conclusion, the first two options I presented here describe the process your computer follows when using the unsharp mask filter. These are great routes to take if you have a bunch of layers or you want to learn more about filters and sharpening photos. The last topic I discussed shows you, hopefully, how the unsharp mask tool really affects contrasting lines so that you can see what it is that your sharpening tool is doing when you use it. Hopefully these thoughts will make you a better photo editor!