Really Smart Sharpening

Current versions of Photoshop feature an improvement over the traditional Unsharp Mask known as Smart Sharpening. Adobe also now lets you turn regular image layers into Smart Objects. If you put Smart Objects together with Smart Sharpening and throw in some simple edge masking magic using the Masks Panel, you can get really smart indeed.

Adobe introduced Smart Sharpening back in Photoshop CS2. Using it is much more intuitive than dealing with the sliders in Unsharp Mask and tends to produce cleaner results especially when dealing with photographic images. But as with most other sharpening methods, using Smart Sharpening is a destructive operation. When you click on "OK" the sharpening effect gets baked into your image. If you later decide you overdid it, it's too late. There's no going back unless you saved a duplicate copy of your image before sharpening it. You can add more sharpening by simply using the filter again, but you really can't lessen the sharpening you've already applied.

Photoshop CS2 also introduced Smart Objects, a clever innovation that allows you to encapsulate an image inside a layer in a way that preserves the contents but still lets you modify it with filters, layer masks and other normal editing techniques. The results look as if you have added saturation or contrast, shrunk it, converted it to black and white, even sharpened it — whatever — but your edits remain editable. Such modifications remain nondestructive, and nondestructive editing is a good thing.

A filter applied to a Smart Object is known as a smart filter. Although Photoshop CS2 was smart enough to have Smart Objects and Smart Sharpening, it wasn't until CS3 that Photoshop was smart enough for Smart Filters. If you have CS3 or above, you can apply quite a few different filters to a smart object. Not all, but many. And yes, Smart Sharpening is one such filter. When you smart sharpen as a smart filter on a smart object you can reopen the sharpening settings later on to fine tune them if you decide you didn't have things quite right the first time around. You can also reopen the image layer if you find you missed cloning out a dust spot or need to tweak something there.

This is great news, but there's one more thing you can do to make a great technique even smarter: add a layer mask designed to limit the sharpening to just the edges where it is needed. By avoiding sharpening background noise you can be much more aggressive in making the edges sharper. I wrote about an edge sharpening technique that was the forerunner to this method back when CS2 came out but wanted to update it to be even ... well, smarter this week. Here's how it works:

First, before you do anything else to your image, right click on the background layer and choose "Convert to Smart Object" from the context menu. Do this right away when you first open the image in Photoshop. Your sharpening needs to be applied to the Smart Object, but you want all your other edits and optimizations to be inside the Smart Object.

Now that you've created the Smart Object, double click on it in the Layers Panel to open it so you can do whatever pre-sharpening edits you may need. Photoshop will open it just as if it were a new image in its own right. You'll see an informational pop-up message informing you that when you are finished editing the image to choose File >> Save to commit your changes. You can also though just click on the "X" next to the title in the tab for that image. You will see a message asking if you want to save your changes to something known as a "PSB" file which is Adobe's new format that supports not only Smart Objects but also large standalone files. PSB files are the same as PSD files except that they can exceed four gigabytes (if you really need files that big). While editing your Smart Object, you can add additional layers and other changes as needed. When ready to sharpen close it and save your changes. Remember that if you do want to come back later and change anything else, you can simply by double clicking on the Smart Object layer icon again. Even after sharpening, you can still make more changes to the Smart Object contents and the sharpening will get applied to them just like everything else, just as if you had made those changes before sharpening. Think nondestructive sharpening. And nondestructive really is smart.

Now for the actual sharpening. With the Smart Object closed, select Filter >> Smart Sharpen from the Photoshop menu. Adjust the Radius and Amount as desired, but don't be afraid of being quite aggressive at this stage. You can come back later and modify your choices later, but if you pump up the Amount now it will help you see what is going on later. Click on "OK" to save your sharpening choices. In the Layers panel, you should now see a new blank layer mask (the white rectangle) named "Smart Filters" together with the actual Smart Sharpen layer hanging underneath your Smart Object.

Click on the "eyeball" icon to the left of the actual Smart Sharpen layer to turn it off. Whatever choices you made in the Smart Sharpen dialog will now be disabled so your image will be back to looking unsharpened. Now select your entire image layer (the Smart Object) and copy it to the clipboard. You can easily do this by clicking on the Smart Object in the Layers panel and pressing Ctl-A followed by Ctl-C (the keyboard shortcut for "Select all" followed by "Copy"). If you're on a Mac, this will be Command-A and Command-C rather than the same letters combined with the Control key as on Windows.

Now Alt-click on the blank white layer mask (Option-click on Mac OS) to display the mask itself in the image editing window. Then press Ctl-V (Command-V on Mac) to paste your clipboard into the mask. Since a mask is only a single channel, you should now see a black and white version of your image in the main editing window.

This layer mask is being applied to the effects produced by the Smart Sharpen layer so if you think about it, as is it will sharpen more in bright areas of the image than in dark areas. Remember, with layer masks, white reveals and black conceals. Obviously what we really want is to sharpen more on edges and less on non-edges, so we need a way to turn the black and white image we have now into something more appropriate. Thankfully, Adobe made this easy by means of the "Find Edges" filter. From the Photoshop menu, select Filter >> Stylize >> Find Edges. You should now see what looks basically like a black on white line drawing version of your original image. Go ahead and use Levels to clean up the result by lowering the white point and raising the black point. If there are any other changes you want to make to clean things up more, feel free to use a white or black brush as needed.

As I mentioned earlier, in a mask white reveals and black conceals. So if you've been wondering how this mask is going to sharpen edges when those edges are black in our mask on a white background rather than the other way around, don't worry. Photoshop CS4 solves this nicely via the new Masks Panel. Also, when I wrote about sharpening in conjunction with edge masking before, I mentioned you should also apply a small amount of Gaussian blur to your mask to help blend things in better but if you are using Photoshop CS4 there's a better way now to blur your mask. And it's a nondestructive way too. Smart, right?

When you are done cleaning up your mask, go to the Masks Panel and click on the Invert button. If the button is grayed out and not available, check that you don't have an active selection. You can't use the Masks Panel at all if anything is currently selected. When you invert your mask, all the black areas will turn white and the white areas will now become black. Rather than a black line drawing on a white background, you should now see a white line drawing on black for your mask.

Go ahead and turn the eyeball icon next to your Smart Sharpen layer back on now to re-enable the sharpening effect. The sharpening will now be applied only where your inverted mask showed white. Since you will probably have a fairly sharp edge to your white-on-black line drawing mask, the image may now look a bit plastic-like with sharp edges but comparatively softer areas between those edges. To blend things in better, use the Feather slider in the Masks Panel to slightly blur the mask. This blur though remains completely editable since it's not really part of the mask but is instead applied dynamically via the slider setting. Think of this as an adjustment layer for your mask.

From this point, you can tweak the Smart Sharpen settings as well as the feathering in the Masks Panel to optimize the appearance of your image.

There is a Density slider in the Masks Panel too which can be somewhat misleading. While you might assume that lowering the Density would fade the overall sharpening effect, but doing so essentially sharpens things more. A less dense mask means that all your blacks become gray so where you had been blocking the sharpening in black areas of the mask, it will now start to show through everywhere. Either leave the Density at maximum and pretend it isn't there or decrease it only slightly if you wish to apply a small amount of sharpening even on non-edge areas of your image.

If you decide to make major changes to your mask down the road you can always reselect your Smart Object image layer and paste it back into the mask, then use Find Edges and so on to recreate it. If you are familiar with the Masks Panel in general, you may have noticed that the various adjustments normally accessible via the "Mask Edges" button aren't available for masks on smart filters. I'm hoping that Adobe remedies this in the next release of Photoshop as they would prove quite useful. If you could get at them, even more of this process would become nondestructive. Even without that, sharpening with this technique gives you a great deal of control and flexibility, with most choices remaining editable later on.

There are countless ways to sharpen images in Photoshop. A typical image shot using good technique will be fine for most purposes with just about any of them. But when you really need to get the best results you can in order to save a marginal image, it can be worth investing a bit more time. Thankfully, once you understand how to employ it, the technique here doesn't really take much longer than basic sharpening methods but it produces far superior results. And that really is smart.

To summarize the steps involved in this technique:

1. Turn original image into Smart Object. Do all your non-sharpening edits inside the Smart Object
2. Save and return to your original image.
3. Over-sharpen with Filter >> Smart Sharpen
4. Disable sharpening by clicking on eyeball next to Smart Sharpen layer
5. Select image and Copy with Ctl-A and Ctl-C
6. Alt-Click on mask layer and paste (Ctl-V) image in as black and white
7. Filter >> Stylize >> Find Edges while editing mask
8. Clean up mask with Levels or other methods as needed
9. Click on Invert in Masks Panel
10. Turn Smart Sharpening back on via eyeball next to layer
11. Feather sharpening with Masks Panel

That's all there is to it.

Date posted: November 22, 2009 (updated November 26, 2009)

Copyright © 2009 Bob Johnson, Earthbound Light - all rights reserved.
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