"Smart Sharpening" for PSP

"What is it in an image that really needs sharpening? Answer: the edges. What if you could use 'Find Edges' to somehow only apply Unsharp Mask to the edges of an image—the parts that actually NEED sharpening—and leave the rest alone? It turns out this is not only possible, but it's relatively straightforward, and it works beautifully. And that's what I mean by 'smart' sharpening, since we are now only sharpening the parts of the image that actually need it."

That's how John Brownlow began his 'Smart-Sharpening' tutorial for Photoshop users in 2001 and laid out the process that became part of the Smart Sharpen filter in CS2 four years later. PSP has Sharpen, Sharpen More, High Pass Sharpen, and Unsharp Mask for sharpening, but so far (Feb 08) no equivalent of Photoshop's Smart Sharpen. Like most other Photoshop features that PSP lacks, Smart Sharpen can be emulated successfully by recent PSP versions. This tutorial tells you how to sharpen your high-resolution photographs the smart way. original image
after unsharp mask after high-pass sharpen
The screenshots are cropped from a photo that could become an 11-by-14-inch print; if your monitor is set at 1024 x 768, you're seeing the seagull as the same size as it would appear printed, though the print wouldn't be limited by the monitor's 72- or 96 ppi display. The image needs to be sharpened because the process of digital capture inevitably softened it. Camera movement, subject movement, focus, aperture, and shutter speed are less inevitable softeners, but one or more usually contribute as well. Sharpen, Sharpen More, and the controllable sharpeners Unsharp Mask and High-Pass Sharpen all affect the entire image instead of just the parts that need sharpening and almost always leave sharpening artifacts. Want to see some?

Scroll this page so that the three pictures are roughly centered in your screen and get out your screen magnifier (find the one that comes with Windows by using the Start Menu » Programs » Accessories » Accessibility; 2X or 3X is enough magnification). Look at the seagull's beak; it's okay in the original (though a little soft), but both Unsharp Mask and High-Pass Sharpen have added a white halo above and below the dark band. Look at the top of the seagull's head; again, the original's okay, but Unsharp mask has blown out (over-whitened) the top line of pixels and over-darkened the adjoining pixels in the sky. High-Pass Sharpen did a better job in this area, but it's just as bad as usm elsewhere. Around the eye and toward the beak and on the front of the throat, both create more blown-out pixels; while some lightening is essential to create the contrast that creates the sharpening, both usm and hps overdo it. (And hps did not, in this picture, make any dark haloes as it frequently does.) They can't help it; they're too stupid to know which pixels don't need lightening, why more contrast isn't better, and when to stop short of  L = 255.

Before you turn off the magnifier, scroll down to the bottom of this page and look at the final result of a sharpening process that is "smart." Want to try it on your own image(s)? Here follow the steps that give PSP a 'Smart-Sharpen' capability. Use them on a number of photographs, think about what you're accomplishing as you repeat the various actions, and you'll be rewarded not just by a few sharper images but also by discovering ways that 'Smart Sharpen' can be educated to make it even smarter.

  1. Make a duplicate layer of the image you want to sharpen. This is going to define which parts of the image we are going to sharpen. We'll use this layer to make the sharpening mask. Name it "map for mask."
  2. Use (Adjust » Color ») Channel Mixer on it to make it into a grayscale image.
  3. Use (Effects » Edge Effects ») Find all. This image, with all the edges isolated, is the basis for the "smart sharpening." Two things about it you need to understand: It is an interim step that keeps smart sharpening non-destructive— until the very last step (and beyond, if you save your layers in a pspimage) your original image remains unharmed. And it is not just a tool but a source of information— it tells you how you're going to apply Unsharp Mask to your image: black areas will be sharpened; white areas will be left alone; dark gray areas will be sharpened more than light gray areas. Yet it is a tool: if that dark line along the neck is an area that doesn't need more sharpening, change it! make it silver or white instead of black in the next step.
image with edges found with background cleared edges emphasized by Levels edges blurred
  1. …which is to adjust the tonality of the map a little so that areas that need sharpening are really dark and anything that doesn't need sharpening at all is actually white. If the background is out of focus, paint it white. Then use (Adjust » Brightness and Contrast ») Levels. To bring up the black point, move the the black 'Input levels' end slider to the right; to bring down the white point, move the white 'Input levels' slider to the left; to fine-tune the process, move the middle 'Input levels' slider one way, then the other, to eliminate most of the grays in the layer.
  2. Now apply a Gaussian blur to the image to make sure the transitions between areas that are sharpened and areas that aren't are nice and smooth. The smoothness prevents those light and dark sharpening artifacts or haloes in the final image. How much blur is up to you, but between 3 and 10 pixels should be enough.
  3. You may want use Levels again, now, to fine-tune the map, which is ready to become a mask.
Review: the black areas represent parts of the image to sharpen, and white areas are the parts to leave alone.  Now, to make a mask that turns this map into a selection of the original image in which the black parts are selected (to be sharpened) and the white parts aren't…

7.  Make another duplicate of the layer you want to sharpen, so the
     Layers palette contains (from top to bottom) the black-and-white
     "map," the new duplicate of the main image layer, and the main
     image layer.
layer palette
  1. Activate the second layer, the duplicate.
  2. Do (Layers ») New Mask Layer » From Image, then select "Source Luminance" and check "Invert mask data."
  3. On the Layers palette make the top "map" layer invisible.
  4. Click on the little mask icon (icon) at the top of the Layers palette. Now you'll see a ruby-colored overlay that covers all but the "map"-outlined parts of the second image. That signifies that this mask hides what's red and shows only those "mapped" parts of the image, the parts to be sharpened. You can click the mask icon again once you've confirmed what's going to be left of the middle layer when the mask is applied.
  5. Apply the mask by Merge » Merge Down (or Delete-yes-merge-mask-with-layer), and ungroup the layer group that now contains only one layer.
  6. Make sure the bottom (original, main) layer is visible and that the middle (masked) layer is activated; its Blend Mode should be Normal.
  7. Here's the actual sharpening: Use (Adjust » Sharpness ») Unsharp Mask on the middle layer, with the radius set to 1, the strength to 300%, and clipping to 0. Check "Luminance only." Use the preview buttons of the Unsharp Mask dialog box (below the preview pane) to see the changes in your image as you make the strength greater than and less than 300% (you can apply a considerable degree of sharpening this way, even 500%, without degrading the image very much). If you want more subtlety, reduce the radius by a quarter of a pixel or so. When you like what you see, toggle the "Luminance" checkbox several times; if leaving it unchecked doesn't cause color-fringing, you may like the slightly stronger effect. Then you can click OK.
  8. Now change the Blend Mode from Normal to Luminance to Overlay to Hard Light to Soft Light and back, on the chance that one of these produces a better image. If the best sharpening doesn't result from the Normal blend mode, you have 'permission' to be somewhat more agressive with the contrast in your edge-maps in the future.
  9. Finally, delete the top "map" layer, merge the remaining two layers, save your file, and you're done.
original PSP smart sharpened

This sharpening technique emulates the effect of Photoshop's (and The Gimp's) Smart Sharpen—I use "emulate" precisely here, for this technique improves on  the Smart Sharpens.  Because it works on a mask, it is totally non-destructive and more adjustable than they are. That you may have to make it harsher (if one of the other blend modes does a better job than Normal does) is a bonus: most other ways to sharpen have to be adjusted in the other direction lest they ruin your images.  Its only shortcoming is that it sometimes produces a (fairly mild) halo effect along high-contrast edges.  If the halo is present and unacceptable, you can edit it out of the edges map after step 4 above, or use the "Gentle Edge Mask."

 "Translated" into PSP from Smart Sharpen Tutorial by John Brownlow (September 2001).

dimpled spider outrageous designs '08

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