Sharpen an image

You use the Edge Sharpen controls to sharpen the detail in your image. Images shot with digital image sensors are often a bit soft in focus because of the demosaic filter applied by the camera’s processor. The Edge Sharpen controls adjust the luminance values in the image, increasing the contrast between light and dark pixels that touch, creating an “edge.” Increasing the contrast between these neighboring light and dark pixels gives the image a crisper, or sharper, appearance. You also use the Edge Sharpen controls when you make noise-reduction adjustments, so that the image retains detail and crisp edges that might otherwise be obscured by the effect of the noise-reduction adjustment. Edge Sharpen adjustments can also compensate for the softening that occurs with some printing processes.

Figure. Image before and after an Edge Sharpen adjustment.

For maximum accuracy, the Edge Sharpen adjustment sharpens the image in three passes that appear to occur simultaneously—an initial sharpening pass, where a majority of the sharpening occurs, followed by two subsequent sharpening passes. These subsequent passes are called falloff.

Important: The Edge Sharpen controls are not designed to correct images that were shot out of focus.

Aperture also includes a sharpening adjustment from previous versions of Aperture. If you applied sharpening in a previous version of Aperture using the Sharpen adjustment, the Sharpen adjustment controls are still there so that your adjustments remain intact and unchanged. However, to do further sharpening on other images, it’s recommended that you use the Edge Sharpen adjustment controls, which generally offer more precise control over how sharpening is applied.

Sharpen an image using the Edge Sharpen controls

Select a photo.
If the Edge Sharpen controls aren’t shown in the Adjustments inspector or the Adjustments pane of the Inspector HUD, choose Edge Sharpen from the Add Adjustment pop-up menu (or press Control-S), and specify the following settings:
- To adjust the strength of the Edge Sharpen adjustment: Use the Intensity parameter controls.
  A value of 0.0 applies no sharpening adjustment to the image. A value greater than 0.0 increases the sharpening adjustment.
- To adjust the threshold for determining which pixels are edges and which ones are not: Use the Edges parameter controls.
  A value of 0.0 applies no sharpening adjustment to the image. A value greater than 0.0 increases the number of pixels that qualify as edges.
  Note: If you observe digital noise beginning to increase in flat areas of the image (areas with little or no contrast), decrease the Edges parameter setting.
- To adjust the amount of sharpening applied in the subsequent sharpening passes: Use the Falloff parameter controls.
  The falloff percentage is applied proportionally to the second and third sharpening passes. For example, if 0.69 (69 percent) is set as the Falloff parameter value, 69 percent of the original amount of sharpening is applied during the second sharpening pass, and 69 percent of the amount of sharpening from the second sharpening pass is applied during the third sharpening pass. In other words, only 47.6 percent of the amount of the original sharpening is applied during the third sharpening pass.

You can also brush the Edge Sharpen adjustment on specific areas of an image. For more information, see Apply brushed adjustments.

Use the Edge Sharpen workflow

The Edge Sharpen adjustment in Aperture is a professional tool that’s used to sharpen photos. Using the Edge Sharpen adjustment controls in conjunction with the following workflow makes it easy to achieve professional results.

In the Edge Sharpen area of the Adjustments inspector or the Adjustments pane of the Inspector HUD, set the Intensity slider to the maximum value to see the effect of the operation.
Adjust the Edges slider so that you can see which parts of the image are being sharpened.
Try to adjust the Edges slider so that edges are sharpened, but noise and texture in the image aren’t affected.
Adjust the Falloff slider so that the edge sizes you want sharpened the most are accentuated.
Decrease the Intensity parameter value until the sharpening effect is appropriately subtle.
Values below 0.5 usually work best.

Sharpen an image using the legacy Sharpen controls

You use the Sharpen adjustment controls when you need to modify Sharpen adjustment parameter settings that were applied to an image in a previous version of Aperture.

Select a photo.
If the Sharpen controls aren’t shown in the Adjustments inspector or the Adjustments pane of the Inspector HUD, choose Sharpen from the Add Adjustment pop-up menu, and specify the following settings:
- To adjust the amount of sharpening applied to the image: Use the Intensity parameter controls.
  A value of 0.0 applies no sharpening adjustment to the image. A value greater than 0.0 increases the sharpening adjustment to the image.
- To adjust the area over which the sharpening adjustment is applied (the distance, in pixels, that Aperture goes from each pixel to evaluate sharpness): Use the Radius parameter controls.
  A value of 0.0 applies no sharpening adjustment to the image. A value greater than 0.0 increases the area over which the sharpening adjustment is applied.

You can also brush the Sharpen adjustment on specific areas of an image. For more information, see Apply brushed adjustments.