Bryson Leidich

Photography and Photoshop

Smart Sharpen


An excellent sharpening tool in Photoshop is the Smart Sharpen filter. It must be applied to a pixel layer, so the best approach is to make a merged visible layer at the top of the layer stack and apply Smart Sharpen at the end of the process. Since sharpening applied to a file should be relative to the image size this will allow easy removal of the sharpening from a psd which can then be resized for output. However, this is also one of the reasons why final global sharpening of most files is best done at the printing stage, preferably using Lightroom.

Roll over the image to the right to see the unsharpened version. Smart Sharpen was applied to this image at 250% at 0.7 pixels with no other parameters set. The effect is apparent pleaasant sharpening with no visible halos or other destructive effects. The image is a portion of an image background and not intentionally sharp to begin with, so the ability of Smart Sharpen is shown here as pretty effective. That also speaks to sharpening effects being applied carefully to specific areas of an image rather than globally.

Smart Sharpen is actually a composite dialog that uses unsharp masking, noise reduction, and blendif capabilities in one dialog. This makes the application easy to use, and works exceptionally well. Absent the need for a different means of sharpening it is the best choice.

The first control is Amount, and in conjuction with Radius it works about the same a Unsharp Mask. It has edge detection as part of the process which makes it less likely to create halos, but still must be used carefully. You can start by lowering the Reduce Noise slider so you can see the full effect of the sharpening.

Increse the Amount slider until you see the sharpening effect you want, either in the image preview or the preview in the dialog box. Most sharpening is best done at 100% image size. At 50% you may see a better indication of how the image will appear on a monitor. If you have used unsharp mask sharpening before you will first notice that Smart Sharpen can be used at a higher amount without negative effects, but even more refinement is possible. I suggest starting at 100% and working with the Radius before increasing the amount.

Increasing the Radius slider will eventually begin to show a crunchy effect, expecially around fine details in otherwise soft areas, like eyelashes or fine tree details. Here you simply need to work the Amount and Radius sliders to come to a compromise that gives you good results. My suggestion is that lower Radius values are better in most cases and I often use a Radius of 1 pixel or less. Start with a low value and increase it as needed. Subject matter makes a big difference as high frequency images will show the sharpening more quickly.

Next would be Noise Reduction. In an image with little noise the effect will be minimal, of course, but check for noise in the darkest areas of the image for the most effective use. Noise reduction always softens an image, so a compromise is usually needed between some noise and complete removal. Less obvious noise often simply disappears in the printing process, so the application becomes one of experience. If the image was captured at a low ISO or otherwise shows little noise, adding Noise Reduction would simply soften the image.

In the "Remove" box you have three choices as to how Photoshop applies sharpening. Gaussian Blur is the default and applies the sharpening to the entire image in a normal manner. Essentially a low pass filter, Gaussian Blur attenuates the high frequency elements of the image to sharpen without having too strong an effect on fine detail relative to the rest of the image. Lens blur attempts to sharpen the image in a manner similar to how a lens creates an out of focus image as the result of overlaying circles of confusion. The result is an inversion of the effect, and usually looks more realistic than Gaussian Blur. Often the differences are very subtle. The third option is Motion Blur which can be helpful if the motion is slight and you can effectively match the direction of the movement.

Since all sharpening relies to some extent on an increase in contrast, the bottom half of the dialog is a simpler application of the Blendif controls. Amount is simply how much to reduce the effect of the sharpening. The tonal width is the percentage of the image tonal range to use to reduce the sharpening effect. I recommend starting with about 50% reduction on 20% on the tonal width of both the shadows and the highlights which would restrict the sharpening to the middle 60% of the tonal range, blending the effect into the values below 50 and above 200. As with all sharpening, the image content will greatly effect the need, and you need to be careful to not overdo the effect.

Less intuitive, and less obvious is the Radius setting which blends the effect into the image based on the edges detected. In small images a smaller Radius can be used and in larger images the blending can be over a greater range. It can be difficult to see depending on the fineness of the image detail. If you can't see a difference on screen at 100% you certainly will not see the difference in a print.