Sometimes your images aren’t as sharp as you’d like. Sometimes your images have a tiny bit of softening caused when scanning an image or perhaps, when capturing a photo on your digital camera. Or, perhaps, you want only a particular part to be sharper so that it stands out from its surroundings. All sharpening tools operate by increasing the contrast between adjacent pixels. If you look at a sharpened image side by side with the original version you’ll see that no new information has been provided. Instead, the contrast is boosted so that edges are more distinct. The dark parts of the edges are darker, and the light parts at their boundaries are lighter.
Photoshop has five main sharpening tools, only four of which are actually filters. The fifth, the Sharpen tool, isn’t a filter, strictly speaking. It’s more like a paintbrush that lets you sharpen areas selectively by using strokes.
The sharpening filters give you more control because you can easily apply them to selections that you carefully craft. Three of the four sharpen filters are single-step filters that you can apply quickly without resorting to dialog boxes.
Sharpen
The Sharpen filter is best used for minimal touchups in small areas. Enable this filter by choosing Filter-->Sharpen-->Sharpen. This single-step filter increases the contrast between all the pixels in the image or selection. Although this makes the image look sharper, it can add a grainy look to solid areas that aren’t part of the edges.
Sharpen More
Choose Filter-->Sharpen-->Sharpen More to use the Sharpen More filter, a single-step filter that increases the contrast between all the pixels even more than the regular Sharpen filter. Like the Sharpen filter, Sharpen More is best relegated to non-critical sharpening because it doesn’t do a very good job of sharpening large areas. Also, it doesn’t provide the control you need for more intense projects.
Sharpen Edges
The Sharpen Edges filter (choose Filter-->Sharpen-->Sharpen Edges) is a single-step filter that’s superior to the Sharpen and Sharpen More filters because it concentrates its efforts on the edges of images, adding sharpness without making the image grainy or noisy. Still, it, too, is best used for quickie fixes.
Unsharp Mask
Don’t feel bad. Everyone is confused by the Unsharp Mask filter’s name the first time they encounter it. (Find this filter by choosing Filter-->Sharpen-->Unsharp Mask.) This filter provides a sophisticated attempt to duplicate a sophisticated photographic effect called unsharp masking, in which two sheets of film are sandwiched together to create a final image. One sheet is the original film negative (or a duplicate), and the second is a positive image (the “normal” photograph) that’s blurred slightly.
When the two are mated together, the light and dark areas cancel each other out, except at the edges — because of the blurring of the positive mask, which causes the edges to spread at those points. Unsharp masking is a tricky procedure in the darkroom. It’s much more precise in the digital realm because Photoshop can easily control the width of the areas to be masked, as well as a relative brightness level to use before beginning to apply the masking effect.
Scanned images almost always benefit from a little unsharp masking, but you should be conservative and not overdo things. That’s especially true because two out of three of the Unsharp Mask controls are not the sort you can apply intuitively. The Radius and Threshold sliders work best when you’ve had some experience using Unsharp Mask. However, the Amount slider is a bit easier to work with. Here’s how to use each of these controls:
- Amount: Use this control to vary the amount of edge sharpening. Your choices range from 1 percent to 500 percent. For subtle amounts of sharpening, anything around 100 percent or less provides the effect you’re looking for without making the image appear overly contrasty (yes, that is a technical term) or unrealistic.
Sharpening always increases contrast, so you should use any of the Sharpening tools before trying other contrast-adjusting tools. When you’ve sharpened your image to your satisfaction, you can then use the other contrast controls to fine-tune the image with additional contrast (if it’s still required).
- Radius: This slider controls the width (in pixels) of the edges, that the Unsharp Mask filter will modify. Your range varies from 0.1 pixel (for fine control) to 250 pixels (for broader sharpening effects). Your use of this control will vary chiefly on the resolution of your original image. Low-resolution images (100 pixels per inch and lower) look best when you use only a small radius value, from a fraction of a pixel up to three or four pixels. A small amount of sharpening may produce no visible effect on high-resolution images, especially those with 300 ppi resolution or more. You may need to move the slider to the 5-pixel range before you see any effects. Regardless of the resolution of your image, setting the radius too high emphasizes the edges of your image unrealistically, and boosts the contrast too much.
A good rule to consider when you select a radius is to divide your image’s ppi resolution by 150 and then adjust from there. For example, if you have a 150 ppi image, set the radius at 1 and then tweak from there.
- Threshold: This slider controls the difference in brightness between adjacent pixels that must be present before the edge is sharpened. That is, you need to have a distinct contrast between adjacent pixels along an edge in order to sharpen the edge. Your choices range from brightness values of 0 to 255. Selecting a low value causes edges with very little contrast difference to be emphasized (which is usually what you want). You’re usually better off leaving this control at 0 unless your image has a lot of noise. Higher values force Photoshop to provide edge sharpening only when adjacent pixels are dramatically different in brightness. Increasing the threshold too much can cause some harsh transitions between sharpened and unsharpened pixels.
In most cases, the Amount and Radius sliders are the only controls you need to use. Threshold is most useful when the first two controls create excessive noise in the image. You can sometimes reduce this noise by increasing the Threshold level a little.
Photoshop has five main sharpening tools, only four of which are actually filters. The fifth, the Sharpen tool, isn’t a filter, strictly speaking. It’s more like a paintbrush that lets you sharpen areas selectively by using strokes.
The sharpening filters give you more control because you can easily apply them to selections that you carefully craft. Three of the four sharpen filters are single-step filters that you can apply quickly without resorting to dialog boxes.
Sharpen
The Sharpen filter is best used for minimal touchups in small areas. Enable this filter by choosing Filter-->Sharpen-->Sharpen. This single-step filter increases the contrast between all the pixels in the image or selection. Although this makes the image look sharper, it can add a grainy look to solid areas that aren’t part of the edges.
Sharpen More
Choose Filter-->Sharpen-->Sharpen More to use the Sharpen More filter, a single-step filter that increases the contrast between all the pixels even more than the regular Sharpen filter. Like the Sharpen filter, Sharpen More is best relegated to non-critical sharpening because it doesn’t do a very good job of sharpening large areas. Also, it doesn’t provide the control you need for more intense projects.
Sharpen Edges
The Sharpen Edges filter (choose Filter-->Sharpen-->Sharpen Edges) is a single-step filter that’s superior to the Sharpen and Sharpen More filters because it concentrates its efforts on the edges of images, adding sharpness without making the image grainy or noisy. Still, it, too, is best used for quickie fixes.
Unsharp Mask
Don’t feel bad. Everyone is confused by the Unsharp Mask filter’s name the first time they encounter it. (Find this filter by choosing Filter-->Sharpen-->Unsharp Mask.) This filter provides a sophisticated attempt to duplicate a sophisticated photographic effect called unsharp masking, in which two sheets of film are sandwiched together to create a final image. One sheet is the original film negative (or a duplicate), and the second is a positive image (the “normal” photograph) that’s blurred slightly.
When the two are mated together, the light and dark areas cancel each other out, except at the edges — because of the blurring of the positive mask, which causes the edges to spread at those points. Unsharp masking is a tricky procedure in the darkroom. It’s much more precise in the digital realm because Photoshop can easily control the width of the areas to be masked, as well as a relative brightness level to use before beginning to apply the masking effect.
Scanned images almost always benefit from a little unsharp masking, but you should be conservative and not overdo things. That’s especially true because two out of three of the Unsharp Mask controls are not the sort you can apply intuitively. The Radius and Threshold sliders work best when you’ve had some experience using Unsharp Mask. However, the Amount slider is a bit easier to work with. Here’s how to use each of these controls:
- Amount: Use this control to vary the amount of edge sharpening. Your choices range from 1 percent to 500 percent. For subtle amounts of sharpening, anything around 100 percent or less provides the effect you’re looking for without making the image appear overly contrasty (yes, that is a technical term) or unrealistic.
Sharpening always increases contrast, so you should use any of the Sharpening tools before trying other contrast-adjusting tools. When you’ve sharpened your image to your satisfaction, you can then use the other contrast controls to fine-tune the image with additional contrast (if it’s still required).
- Radius: This slider controls the width (in pixels) of the edges, that the Unsharp Mask filter will modify. Your range varies from 0.1 pixel (for fine control) to 250 pixels (for broader sharpening effects). Your use of this control will vary chiefly on the resolution of your original image. Low-resolution images (100 pixels per inch and lower) look best when you use only a small radius value, from a fraction of a pixel up to three or four pixels. A small amount of sharpening may produce no visible effect on high-resolution images, especially those with 300 ppi resolution or more. You may need to move the slider to the 5-pixel range before you see any effects. Regardless of the resolution of your image, setting the radius too high emphasizes the edges of your image unrealistically, and boosts the contrast too much.
A good rule to consider when you select a radius is to divide your image’s ppi resolution by 150 and then adjust from there. For example, if you have a 150 ppi image, set the radius at 1 and then tweak from there.
- Threshold: This slider controls the difference in brightness between adjacent pixels that must be present before the edge is sharpened. That is, you need to have a distinct contrast between adjacent pixels along an edge in order to sharpen the edge. Your choices range from brightness values of 0 to 255. Selecting a low value causes edges with very little contrast difference to be emphasized (which is usually what you want). You’re usually better off leaving this control at 0 unless your image has a lot of noise. Higher values force Photoshop to provide edge sharpening only when adjacent pixels are dramatically different in brightness. Increasing the threshold too much can cause some harsh transitions between sharpened and unsharpened pixels.
In most cases, the Amount and Radius sliders are the only controls you need to use. Threshold is most useful when the first two controls create excessive noise in the image. You can sometimes reduce this noise by increasing the Threshold level a little.
Sharpening What’s Soft in Photoshop
![Sharpening What’s Soft in Photoshop]()
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