New To CS2: Blur And Sharpen Filters

The first in our three-part series on what’s new to Photoshop CS2 deals with new blur and sharpen filters—probably the most important filters for those working with photography and layering. We’ll take a look at these latest additions and learn new ways to use them.

The first in our three-part series on what’s new to Photoshop CS2 deals with new blur and sharpen filters—probably the most important filters for those working with photography and layering. We’ll take a look at these latest additions and learn new ways to use them.



Figure 1: Our new Blur filter menu.

The previous Photoshop iteration, CS, introduced the Lens Blur; CS2 introduced no less than three new blurs: the Box Blur, Shape Blur and Surface Blur. I don’t think that any of them will become your blur of choice: Gaussian Blur is still the best choice for an all-around solid blur. The new blurs are more for special effects. There are, however, some tricks with the new blurs that may be the perfect choice for a special situation.


Figure 2: Box Blur at left, 20px radius; Gaussian Blur at right, 20px radius.

The Box Blur is actually a good general-purpose blur and it runs up to four times faster than the Gaussian Blur filter, so if your machine is slow to execute filters such as blurs, a Box Blur may save you some time and turmoil. Remember that the Box Blur tends to leave some horizontal and vertical edges, especially when you have strong edges in your image to begin with. Look at Figure 2, a modified image of a sunflower: both blurs are executed with a 20px radius, but you can see how the Gaussian Blur (at right) created a smooth blur but the Box Blur not only didn’t eliminate the edges and details of the petals but created a boxy effect with horizontals and verticals.


Figure 3: Time to see the Box Blur in action!

The Box Blur filter does this in a big way when you have just the right image, like in Figure 3: a texture from Wetzel & Company. The high contrast will help pronounce the blur and the existing horizontals and verticals will only be stronger after a Box Blur effect. Figure 4 is our control blur, a Gaussian Blur with radius of 4 pixels.


Figure 4: Gaussian Blur, 4px radius.

Now let’s do a Box Blur at the same radius setting (Figure 5):


Figure 5: Box Blur, 4px radius.

The Box Blur makes me bleary-eyed! There’s a lot more “vibration” going on in this blur. Now see what happens with a Box Blur with 10px radius (Figure 6) and 20px radius (Figure 7):


Figure 6: Box Blur, 10px radius.


Figure 7: Box Blur, 20px radius.

Similar textures have been created in the past with the Motion Blur, Radial Blur and Texturizer tricks, and now the Box Blur filter joins their ranks.

Pretty cool textures! Similar textures have been created in the past with the Motion Blur, Radial Blur and Texturizer tricks, and now the Box Blur filter joins their ranks. Ditto the Shape Blur, which applies a vector image while blurring in a way that imparts the shape to the blur. If you use an X shape, for example, the blur will emanate in diagonal directions. This is the same trick as the Box Blur—imagine the Box Blur as a Shape Blur using a square as the vector image! If you’re looking for a wacky special-purpose blur for a texture or strange effect, the Shape Blur will give you more options. You can even create a vector shape, add it to your custom shape collection, and use it as a Shape Blur.


Surface Blur, the third and final new blur filter, is actually a welcome addition to the Photoshop bag of tricks! What it does is blur small details while maintaining the sharpness of larger edges—effectively cleaning up the image. At smaller radii it looks almost exactly like a regular Gaussian Blur, but at larger radii the blur becomes almost a glow and some of the edges return. Ben Willmore has a couple techniques with the Surface Blur filter, including using it before Filter –> Sketch –> Find Edges (to eliminate all the edges that filter returns) and applying the filter to a copy of a layer and blending it for greater control. There are two techniques I can think of that are easy and fun with Surface Blur:

“Star Trek” Beauty Blur: Fans of the original “Star Trek” know what I’m talking about—whenever an attractive woman was on that show, they always had a soft glow all over them. Applying a Surface Blur with radius of 50px and threshold of 255 (full throttle) will create a very similar glow! At those levels the details are blurred out but I use the Art History brush to bring them back. See Figure 8 for the example.


Figure 8: The “Star Trek” Beauty Blur in effect.

Posterization: Making a photo look like an illustration by eliminating detail and simplifying color is a valuable trick to know; the Surface Blur makes it fairly easy. I don’t think it’s the best way to do this—there are other techniques that can do it better, and Surface Blur can leave a glow if you go too far—but on some images with flat color it works very well. Figure 9 shows such an image, and with radius of 30px and threshold of 30 the Surface Blur will return Figure 10.


Figure 9: The original image.


Figure 10: A posterization effect with Surface Blur.


Unsharp Mask has been the old warhorse for Photoshop sharpening for years now, and I don’t think the Filter –> Sharpen menu has had a new addition at least since I started using the application with 3.0, so when CS2 introduced the Smart Sharpen filter it was big news and several mentions of it were made around Photoshop professionals. I don’t hear it mentioned anymore, and I don’t use it. I think Smart Sharpen has two strikes against it: (1) the Basic interface is almost exactly like Unsharp Mask, and the two new additions to it aren’t particularly useful, and (2) the Advanced interface basically controls the strength of the shadow and highlight halo that creates the sharpening effect, but most sharpening is done so haloes aren’t so pronounced. It should be said, though, that if for some reason such excessive sharpening is necessary, it works very well and is a good replacement for Dan Margulis’ three-layer technique that is in his Professional Photoshop book.

When CS2 introduced the Smart Sharpen filter it was big news. I don’t hear it mentioned anymore, and I don’t use it.


Figure 11: The basic Smart Sharpen interface.

Figure 11 shows you the basic Smart Sharpen interface, which is very similar except the missing Threshold setting and addition of the Remove menu and More Accurate checkbox. Some would say the Threshold setting is necessary for a good sharpening, and though I do use it to fine-tune my Unsharp Mask moves I don’t really miss it here. A Radius slider that was more sensitive would work just as well. Let’s focus on the two additions:


Figure 12: Smart Sharpen without More Accurate (left) and with (right).

The More Accurate checkbox will make Photoshop sharpen the image in two passes rather than one. Figure 12 below shows a single pass on the left and double pass on the right. I find this addition to be pretty useless, because (1) it takes more computing time and power to calculate two passes, and (2) it tends to sharpen grain and JPEG artifacts—notice the image on the right of Figure 12 has some extra artifacts around its edges.

The Remove pop-up menu basically gives you greater control over the actual calculation that goes into the sharpening. There are three settings:

  • Gaussian Blur produces the same math used in the Unsharp Mask filter.
  • Lens Blur produces less halo and thus can create a better-quality sharpening.
  • Motion Blur produces even less halo than Lens Blur and but also creates a motion blur effect. This can actually cancel out existing motion blur due to camera movement, but it can only neutralize a very minor amount and I wouldn’t rely on it if I were a jittery photographer.


Figure 13: From left to right: Remove Gaussian Blur, Lens Blur, and Motion Blur.

Figure 13 shows the difference between these three setting; I’ve bumped up the sharpening to maximum levels to illustrate it better. Motion Blur can actually create some cool motion blur effects (see Figure 14 for a combination motion blur/glow effect) but, again, for most of your everyday sharpening the Remove menu is not going to make much difference to your images.


Figure 14: Maximum Smart Sharpen with Remove Motion Blur can create some cool effects.


Switching to Advanced Mode grants you access to two tabs: Shadow and Highlight, each one with the same sliders (see Figure 15) you will find in the extra options of the Shadow/Highlight dialog box, which was introduced with Photoshop CS. It appears Adobe is still pushing Photoshop forward by offering greater control over traditional techniques.


Figure 15: Smart Sharpen’s Advanced settings.

Remember my comment earlier about Dan Margulis’ three-layer technique? This is where it gets recreated. Basically the technique is about isolating the shadow and highlight parts of the sharpening halo so you can tweak them separately. Dan did this with layers, one set to Darken and one set to Lighten, thus revealing just the halo shadows in one and halo highlights in another. Smart Sharpen does practically the same thing in an easy-to-use interface, though Dan’s technique does allow you to tweak the mix later with the layers’ opacity sliders.

Because the sliders in Advanced Smart Sharpen work the same as in Shadow/Highlight, I won’t delve into them here in detail. Basically the Fade Amount will reduce the strength of the sharpening for shadows or highlights, and Tonal Width and Radius will allow you to tweak the range of that effect. And, again, I find controlling my sharpening so closely is not really advantageous to my usual sharpening work. I still use Unsharp Mask and probably will continue to use it. If I could ask Adobe for one thing to help my sharpening, it would be an improved Unsharp Mask that could tell the difference between real detail and worthless artifacts or grain. I think the technology can do it, but it’s a matter of getting the right algorithm that can distinguish the two.