Sharpen Filters


One of the most common problems photographers face is the out-of-focus picture. There are many reasons why a picture might be fuzzy. Either the subject or the photographer might have moved slightly when the picture was taken. Perhaps the camera wasn't focused correctly, or possibly the picture was taken with an inexpensive camera that had a poor quality plastic lens. Some of these problems are easier to compensate for in Photoshop than others.

If a photo is way out of focus, there's not much that can be done to bring it back. If it's just a little bit soft, Photoshop can at least create the illusion of sharper focus. It does this with a set of filters called Sharpen . Like all the filters described in this hour , they're found on the Filter menu (see Figure 14.1).

Figure 14.1. The Filter menu showing the Sharpen filters.


Sharpen, Sharpen More

Two of the Sharpen filters, Sharpen and Sharpen More, provide different levels of the same function. They work by finding areas in the image where there are significant color changes, such as at the edges of an object. Whenever such an area is found, Photoshop increases the contrast between adjacent pixels, making the lights lighter and the darks darker . Figure 14.2 shows three views of a slightly fuzzy picture of rocks in the desert. The top example is before sharpening. The middle example has had Sharpen applied, and the bottom example has had Sharpen More applied. If you don't enlarge the picture too much, the effect looks quite good.

Figure 14.2. Before and after sharpening.


Be careful not to overdo the sharpening. With many Photoshop filters, a little is good but more is better. Alas, this is not the case with the Sharpen filters. Because of the way that the filters enhance contrast in adjacent pixels, you might be just a click away from turning your photo to patchwork , as in Figure 14.3.

Figure 14.3. An image that has been over-sharpened.


By the way, Sharpen More is approximately the same effect as applying the Sharpen filter twice to the same picture. Keep in mind that you can do this any time a filter has less than the desired effect. The easy way to apply the same filter again is to press Command+F (Mac) or Control+F (Windows). This keyboard shortcut applies whatever filter and filter settings (if any) you applied last.

Try the Sharpen filter on one of your own fuzzy pictures and see what you think. Does it help? Try the Sharpen More filter also. They are great for adjusting slightly out-of-focus photographs or scans , but don't rely on these filters too much. They can only do so much. They can't add what is missing from an imagenamely, focus and good contrast. They can, however, help bring back a photo that's just a little bit off. Don't forget that you can apply filters selectively, using masks or selections to only filter part of the image.

Sharpen Edges

Sharpen Edges is a truly useful filter. It doesn't affect the whole image, so you don't get as much of a sense of that harsh blocky effect as with Sharpen More. Rather, Sharpen Edges "sees" and enhances the contrast at whatever it perceives to be an edge. Figure 14.4 shows before and after versions of the desert, using Sharpen Edges. Sharpening the edges has a slight but noticeable effect on the quality of the photo.

Figure 14.4. You can really see the Sharpen Edges effect in the foreground grass.


Unsharp Mask

Unsharp masking is a traditional technique that has been used in the printing industry for many years . It is probably your best bet for precision sharpening. It corrects blurring in an original image or scan, as well as any blurring that occurs during the resampling and printing process. The Unsharp Mask filter works by locating every two adjacent pixels with a difference in brightness values that you have specified, and increasing their contrast by an amount that you specify. It gives you real control of the sharpness of an image.

Set the level of sharpening you need in the Unsharp Mask dialog box shown in Figure 14.5; the dialog box appears when you select the filter. The Radius control sets the number of surrounding pixels to which the sharpening effect is applied. I suggest that you keep the radius fairly lowaround 2.0. The Threshold setting controls how different the pixels must be to be sharpened. The lower the setting, the more similar the pixels can be and still be affected by the filter. The higher the setting, the greater Photoshop's tolerance of differences will be. (Of course, as always, feel free to go wild and try all the settings. That is the best way to learn.) Be sure that you check the Preview box so that you can see the effect of your changes.

Figure 14.5. The preview area lets you see the effect your settings have.


Many Photoshop experts recommend applying the Unsharp Mask filter to every image that you process, whether it's going to be printed or used on the Web. (I personally don't like to say always or never because there can be exceptions to any rule.) You should probably try it on every image, to see whether you like the effect.

Double Duty Filters

Photoshop filters aren't restricted to Photoshop. Other Adobe products, such as PageMaker and Illustrator, can use many of them also. Even Paint Shop Pro and Macromedia's Director can employ many Photoshop filters. If you find particularly useful or interesting filters or filter combinations, try using them with other Photoshop plug-in-compatible programs.



Smart Sharpen

For the ultimate in sharpening power, you can turn to the Smart Sharpen filter, which is new to Photoshop CS2. With this filter, you can choose different sharpening algorithms, or styles, for different kinds of images, and you can control the amount of sharpening in dark and light areas of your image.

Choose Filter Sharpen Smart Sharpen to see the Smart Sharpen options (see Figure 14.6). First, choose an option from the Remove pop-up menu. To fix a generally soft image, choose Gaussian Blur, which uses the same sharpening technique that the Unsharp Mask filter uses. If your image has a lot of detail and needs a pretty hefty amount of sharpening, choose Lens Blur to sharpen edges without adding "sharpening halos " (as shown back in Figure 14.3). And if your camera moved just as you shot the photo, choose Motion Blur and set the angle to match the angle of the blur you see in the image. Finally, unless youre in a hurry, check the More Accurate box so that Photoshop will take a little more time on its calculations and produce the best possible result.

Figure 14.6. The Smart Sharpen filter packs a lot of power into a single dialog box.

In Advanced mode, you'll see two tabs in addition to the Sharpen tab, where you've just made your basic settings. If you're seeing too much effect from the basic settings, but only in the shadows or only in the highlights, drag the Fade Amount slider to the left to reduce the amount of sharpening just in those areas. Drag the Tonal Width slider back and forth to determine how much of the image constitutes "shadows" or "highlights"the higher the setting, the greater the area affected by your Shadow and Highlight tab settings. And the Radius slider controls how much of the area around each pixel Photoshop uses to decide whether that pixel falls into the category of a shadow or a highlight; unless you're feeling adventurous, you can leave this setting alone and get perfectly fine results.



Teach Yourself Adobe Photoshop CS 2 In 24 Hours
Sams Teach Yourself Adobe Photoshop CS2 in 24 Hours
ISBN: 0672327554
EAN: 2147483647
Year: 2005
Pages: 241
Authors: Carla Rose

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