Digital Light & Color

I regularly see PS sharpening recommendations of Radius of say 0.2 to 0.5 pixels with Amount or 200% to 300%. Has anyone any thoughts as to why this is recommended? Until Advanced Sharpen came along, this was not even possible because only integral radii are recognized in the Sharpen dialog. This suggests to me that Jonathan does not consider the typical PS recommendation particularly useful or important. I am surprised at how useful plain old simple Sharpen and Heavy Sharpen are compared to the "sophisticated" Unsharp Mask and Bilateral Sharpen. Any thoughts or comments, especially from Johnathan, as to the rational for the typical PS sharpening recommendation? Thanks.

Cheers, Peter

I don't know how PS implements gaussian blur (which is integral to sharpening) so I can't comment on their particular recommended settings. The ideal sharpening radius generally depends on how blurry the original image is, so I don't believe it makes sense to have recommended settings for all images. The blurrier the image, the larger the ideal sharpening radius. The sharpening amount is a matter of personal taste and again may vary with the subject matter. Contrastier images with sharp edges will start to exhibit halos with smaller amounts than softer images. Sharpen and Heavy Sharpen work best for images that are only slightly blurred. The new bilateral sharpening is also worth experimenting with as it supresses halos which still allowing heavy sharpening, and the radius and amount are both continuously variable.

A couple of additional comments on sharpening in PWP.

The term frequency is often used to describe image content where, for example, feathers on a bird or hair in a portrait have high frequency while the sky or blurry areas have low frequency. The PS recommendations of fractional radii and large amounts are appropriate for sharpening high frequency portions of an image. Sharpening low frequency areas of the image calls for larger radius.

For those who subscribe to the three-phase sharpening approach of Capture, Creative, and Output sharpening developed by Bruce Fraser, the Capture Sharpening phase calls for a light hand and will often use fractional radii (along with edge masks and emphasis on midtones and emphasis on the subject).

PWP Advance Sharpen was developed, in part, to offer fractional radii to sharpen fine detail where a large radius (greater than one) can actually obscure detail rather than enhance it.

I use Advance Sharpen almost exclusively because:

• It has fractional radii.
  
  The on-board edge mask allows sharpening edges while avoiding smooth areas where the image gremlins of noise, dust, and specks are more problematic and sharpening will make them worse.
  
  My tests show the sharpening effect delivered by Adv Sharp is considerably more accurate than with USM.
  
  For me, Adv Sharp is the optional way to sharpen downsized images headed for email. Output size and medium are the major factors in determining the radius for Output Sharpening.

Masking certain areas or applying sharpening by painting can be advantageous because different parts of the image have different frequency and call for different sharpening radii. The new texture mask also offers a convenient way to sharpen edges and avoid smooth areas and is more convenient than the traditional Roberts and Sobel edge masks.

I’m sure that Bilateral Sharpening offers new opportunities in sharpening, but I am not that practiced with it yet.

Jim