In the previous article, we looked at the application of two mainstay sharpening commands in Photoshop: Unsharp Mask and Smart Sharpen. These commands may sometimes seem like magic, but under the hood they’re performing three practical jobs: edge-detection, blurring, and masking. You already know about blurring and masking, and in this article, you’ll see how to use the edge-detection capabilities of the Emboss and High Pass filters to create hand-tuned sharpening effects that can take you further than Smart Sharpen and USM in certain special cases.
We’ll also look at how a Remove option called Motion Blur can address camera shake, along with a little-known sharpening tool that Adobe fixed without fanfare in Photoshop CS5.
This article is based on Chapter 15, Sharpening Details, from Deke’s comprehensive video course Photoshop CS5 One-on-One: Advanced for lynda.com.
Dealing with Camera Shake
In low light situations, you often need to keep the shutter open a long time to get a proper exposure. Hand-holding even a lightweight camera at 1/30 sec or longer will typically introduce “camera shake,” which is motion blur induced by movement of the camera itself. In such shots, still objects will look as if they are moving. With heavier cameras and lenses, you can see this effect at shutter speeds of 1/60 sec or even faster.
Two Photoshop techniques can be used to address the issue. The first approach is to use Smart Sharpen and set the Remove method to Motion Blur. The filter works well with mild camera shake, but cannot correct strong shake.
- “Jump” a copy of the Background layer by clicking on the Background and hitting Ctrl/Command + J.
- Select Filter > Sharpen > Smart Sharpen from the menu bar to open the Smart Sharpen dialog.
- Switch the dialog to Basic mode.
- If you saved your default settings in the previous article, you can use the menu to switch settings back to the defaults, or you can enter them. (Amount = 100%, Radius = 1px, Remove = Gaussian Blur, More Accurate Off.) This will be your starting point for further adjustments.
- Increase the amount temporarily. You can go to 500% in order to exaggerate the sharpening and see what you’re doing.
- Set Remove to Motion Blur.
- Look at the image and try to assess which direction the camera swung, and then set the angle line to match the direction of movement.
- Very often, either zero or 90 degrees work well, but you may also find that some oblique angle is more appropriate.
- Leave More Accurate turned off. Combining it with Motion Blur generally produces disasterous results.
- Click in the radius box to place the focus there, then use shift + up arrow to bump the setting in increments of one pixel. (Using the up arrow by itself nudges the value 0.1.) As you adjust the radius, the image will appear to move around. You’re trying to match the radius to the amount that the camera drifted during the exposure.
- Adjust the amount setting. You can compare before and after to check your settings: click and hold in the preview area of the dialog to see the before version, and release to see the after version.
Removing camera shake with the Emboss filter
The Smart Sharpen filter can do a good job of removing motion blur, but it can also increase noise to an unacceptable level. When that happens, an alternative method is to apply the emboss filter. As surprising as that might sound, it produces an effect that can reduce the appearance of motion blur with significantly less noise.
When you apply the Emboss filter to a layer, it produces an image that looks like what happened to Han Solo in Star Wars Episode V—It’s as if the filter has encased your image in carbonite. What the filter is doing is creating a copy of the layer, inverting the copy, reducing the opacity to 50% and then offsetting the copy according to the angle and height settings you enter.
Here’s how to apply the Filter:
- Jump a copy of the background layer (use Ctrl/Command + J).
- Select Filter > Stylize > Emboss from the menu bar.
- Set the Angle to match the direction of the motion blur.
- Adjust the Height setting to half the value you used for the radius in the Smart Sharpen dialog, rounded to the nearest whole number.
- Set your amount to the same value you used in Smart Sharpen. Click OK to apply the filter.
At this point, the image will have that odd, carbonite look, with lots of gray areas. We’ll use one of the Contrast blending modes to make the grays drop away.
Often the layer will also contain weird colors in some places. Well fix that in the next step.
- Select Image > Adjustments > Desaturate to remove all of the colors.
- Use a contrst blending mode to apply the effect. When in doubt, use the Overlay mode. You can use the Hard Light and Linear light modes for progressively stronger effects, or down-shift the effect by either reducing opacity or using the Soft Light mode.
Sharpening with the High Pass filter
Sharpening works by brightening the light side of an edge and darkening the dark side. Given that, it’s always possible for the sharpening effect to cause tones to clip to black or white, resulting in a loss of detail. Sharpening with the High Pass filter can help avoid that clipping. The technique is ideal for portraits. To be effective, the technique requires a more delicate touch than Smart Sharpen and USM. It’s also not super-intuitive. But, once you get the hang of it, you can make it work well.
The High Pass filter emphasizes edges by surrounding them with small haloes and graying-out anything that is not an edge. Perhaps counter-intuitively, increasing the radius reduces the effect of the filter. We’ll apply the High Pass filter to a copy of the background and blend it to create the sharpening effect.
- Duplicate the Background layer
- Select Filter > Other > High Pass from the menu bar.
- Set the radius according to your output.
- For screen, keep the value very low, in the range of 0.3 to 0.5.
- For print, apply 1 px of radius for every 100 px of output resolution for print (usually around 3).
- Click OK to apply the filter
- Desaturate the layer to remove color aberrations. (Use Shift + Ctrl/Command + U)
- Select a contrast blending mode to apply the sharpening:
- Use Overlay mode as the default
- Linear light to intensify
- Reduce the Opacity value if the effect goes too far
The New and improved Sharpen Tool
Prior to Photoshop CS5, the Sharpen tool had been virtually useless, and more damaging than the old Brightness/Contrast. In Photoshop CS5, Adobe fixed the Sharpen tool and released the new version with barely any acknowledgment. What changed was the addition of the Protect Detail feature. By default, the check box is on, and that’s the way you should use it.
The Sharpen tool is located about halfway down the Tools panel, sharing a button with the Blur and Smudge tools. The tool has no radius control, so it’s really just for screen sharpening. It can be applied directly to a layer, but a better way to work is by sharpening into an empty layer. You drag the tool inside the image to paint the effect onto details that you want to sharpen.
- Add a blank layer above the layer(s) to be sharpened
- Select the Sharpen tool in the Tools panel
- Check the Sample All Layers box in the Tool Options bar
- It’s best to use the default strength of 50%. (You can increase if you’re impatient with the results, but low and slow is a better way to work.)
- Change the mode to Luminosity
- Paint the effect onto the empty layer. The tool copies details from below, sharpens them, and applies the result to the blank layer as you drag the brush inside the image area.
Refining the Sharpen tool’s application
Once you’ve applied the sharpening, you will probably see some areas that have unwanted artifacts, or where you might want to slightly reduce the amount of sharpening. Since you’ve applied the sharpening in its own layer, you can simply remove the unwanted artifacts with the Eraser tool.
- Click the Eraser or tap the E key to activate it
- Tap a number to set a reduced opacity (e.g. tap 5 for 50% opacity).
- Use the square bracket keys to change the size of the Eraser (the [ and ] keys, to the right of the P key).
- The Eraser’s hardness has a default setting of 100%. Use Shift + [ (left square bracket) to decrease its hardness setting. Shift + ] (right square bracket) increases the hardness setting.
- After the sharpening is touched-up, you can reduce the opacity of the sharpened layer to moderate the sharpening.
- You can adjust the layer opacity via the keyboard: Switch to one of the selection tools (e.g., the Marquee tool) and tap a number. For example, tapping 6 will reduce the opacity to 60%.
So, there you have it—several sharpening techniques that go beyond the pre-defined Smart Sharpen and Unsharp Mask filters. Beyond what you’ve seen here, the High Pass filter is the foundation for a range of techniques for adding sharpening and clarity to an image.
By applying your sharpening to a copy of your layer or painting into a blank layer, you get the ability to modulate its application or revise your sharpening at a later date.