Blur Filters
The Blur filters (Filter
Figure 14.7. The Blur menu.
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Blur, Blur More
There are two basic Blur filters: Blur and Blur More. They do exactly as their names suggest. Blur is very subtle. Blur More is only a little less so. Figure 14.8 shows a comparison of the two filters in use, against a nonblurred original. As you can see, the changes are minor. Blurring doesn't make much difference, but it can smooth out wrinkles in a portrait or soften a hard edge.
Figure 14.8. Blur is applied on the top right; Blur More, on the bottom right. You have to look carefully to see the effect.
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Gaussian Blur
You can apply the Blur filter several times to get the effect you want, or you can move on to Gaussian Blur (Filter
Figure 14.9. Smaller numbers give you less blur.
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Figure 14.10. Selective blurring is a helpful tool.
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Which Blur, When?
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Smart Blur
The Smart Blur filter (Filter
Figure 14.11. Experiment with the settings until you find the right combination of Radius and Threshold.
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- In Normal mode, the preview area shows the effects of the blurring.
- Edge Only shows you the outlines with which Smart Blur is working.
- Edge Overlay shows the outlines as white lines on top of the image.
You can use the Edge Overlay or Edge Only to help you determine which Threshold value to set. Convert the mode back to Normal before you click OK to apply the effect.
Surface Blur
Even more than Smart Blur, this filter blurs an image's surfaces and background areas without obscuring edges. It's a good way to get rid of "noise" in old or re-scanned photos, although it doesn't offer as much control as Smart Blur. The controls work just like those in the Gaussian Blur dialog box.
Radial Blur
The Radial Blur filter can be interesting, if you carefully choose how to apply it. It gives you two choices: Spin and Zoom. Spin mode gives you a blur that looks as if the image is spinning around its center point. Zoom mode theoretically gives you the effect of zooming the camera into or away from the image.In the Radial Blur dialog box, shown in Figure 14.12, you can set both an amount for the blur effect (from 1100) and a quality level (Draft, Good, or Best). Amount refers to the distance that the pixels are moved to create the blur. You can see the difference in the Blur center area as you set the blur amount. You can click and drag in the same area to determine a center point for the blur effect.
Figure 14.12. The same dialog box applies both the Zoom and Spin methods.
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Figure 14.13. Spin and Zoom obviously aren't for everyday use, but, as a special effect, they're certainly interesting.
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Motion Blur
When we see lines drawn behind a car, a cat, or a comic strip character, we instinctively know that the subject is supposed to be in motion. Those lines represent motion blur , which is actually a photographic mistake caused by using a slow shutter speed on a fast subject. The image's subject appears totally or partially blurred against the background because the subject actually traveled some distance during the fraction of a second that the camera shutter was open.In the early days of photography, motion blur was a common occurrence, primarily because shutter speeds were slow, and film sensitivity was not very great. Today, motion blur is unusual, unless the photographer is capturing the subject this way on purpose by using the least sensitive film available or by using a small lens opening and a correspondingly slower shutter. If you want to try to approximate the effect of motion blur, Photoshop gives you a tool that can do it.The Motion Blur (Filter
Figure 14.14. Using the Motion Blur filter is tricky at best.
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Figure 14.15. You can't run standing still.
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Figure 14.16. Using layers lets you apply different filters or different degrees of filter to the same image.
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Lens Blur
The lens blur filter attempts to simulate the "real-world" phenomenon in which lens flares and highlights take on the shape of the camera iris. Depending on the number of leaves in the camera shutter, the shape can be a hexagon or pentagon. Photoshop takes it a step further, letting you select from three to eight sides on the highlight, and how much of the image is involved. You can apply it to the entire photo, to a selection, or to a layer.The most important thing about lens blur is that it can vary the amount of blur in different parts of the image based on the current selection. This adds depth of field to the image, so you can focus attention on the objects in the foreground and blur the objects in the background.
Average Blur
Taking blurring to the max, the Average Blur filter mixes all the colors in an image or the selected area to come up with the color that's the average of them all. Among other applications, it's a great way to choose a color that goes with everything to use for backgrounds and type.
Shape Blur
If you have some playing-around time, consider devoting some of it to this filter. Shape Blur bases its blur on an irregular shape of your choosing, repeating that shape throughout the image and applying the blurring effect more in darker areasof the shape. This results in a very subtle effectfor example, a slight starry sparkle can show up in an image blurred using a star shape. In addition to choosing a shape, you can determine how large the "kernel" image is using the Radius slider. The larger the kernel, the greater the blur effect.
Box Blur
I'm really not sure what Adobe intended Photoshop users to do with this new filter. It works like the Gaussian Blur filter, and it does pretty much the same thing, only less smoothly. An image blurred using Box Blur has more pronounced detail than the same picture blurred using a Gaussian blur with the same radius setting. Feel free to experiment, and if you figure out what Box Blur is good for, drop me an email!