HDR software is most typically used to render shadow and highlight detail, but it also can be used to enhance tonal separation and detail in any range of tones, even in images with extremely low contrast. The very same tools that are used to compensate for HDR side effects can be used to sharpen any image.

When multiple bracketed exposures are merged into a single processed file, shadows and highlights that exceed the dynamic range of a camera’s sensor are compressed into the dynamic range of a digital file, taking the midtones with them. Depending on the HDR software used, a variety of tools are available to restore contrast and separation in midtones. If used aggressively, these tools produce the telltale signs of contemporary or grunge HDR artifacts: halos and texture accentuation. These are the very same artifacts that digital sharpening routines use more conservatively to make images appear sharper—only they look different.

Unlike the hard halo and line produced by the filter Unsharp Mask and more like the soft line produced by the filter High Pass, HDR sliders can give you still more points of control over line and texture, each with a slightly different flavor.

Find details on using Adobe Photoshop and NIK’s HDR Efex Pro.

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Different sharpening techniques make the world look different. A world of difference can be seen between the thin hard line of Unsharp Mask and the broad feathered line of High Pass Sharpening.Can you choose a combination of both? Yes, you can! You can choose the texture of one, the halo of another, and the line of yet another, applying them either globally or selectively. You can customize the look and feel of detail in any image or image area with astonishing precision and flexibility.

Double Pass Sharpening

Results will differ if you filter the same image layer twice. Why? First, either the technique or the settings can be varied. Second, having been filtered once, the state of the pixels will have changed before a second pass is applied, generating a different final effect. Consequently, not only the type and amount of filtration matters, but also the order in which the filtration is applied.

Are there benefits to filtering more than twice on the same layer? Maybe. Maybe not. You get diminishing returns with each additional pass of filtration. You may also run the risk of producing more unintended artifacts. Furthermore, as complexity rises, your ability to both predict and interact with the final effect diminishes. In general, I recommend you to be cautious of highly complex routines and urge you to ask yourself if you derive significant benefit from them.

Hybrid Sharpening

Sharpening results also will differ if you apply varied filtration techniques to separate layers. Here, the order of the layers in the layer stack matters.

To combine the effects of the different layers, use Blend modes. Darken will display the only values on a sharpening layer that are darker than values on layers below it, such as the dark line. Lighten will display the only values on a sharpening layer that are lighter than values on layers below it, such as the halo.

High Pass sharpening layers (or any technique that reduces an image layer largely to gray values) combine easily with other layers using Blend modes (typically, Overlay); they do this so well that many times it doesn’t matter whether they’re placed above or below other sharpening layers.

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Both NIK’s Viveza and Color Efex Pro offer useful additions to a digital artist’s set of detail enhancement tools. Viveza provides Structure while Color Efex Pro provides Tonal Contrast. Consider them both useful variations of the types of effects you can produce with Photoshop’s High Pass filter. So what specifically are the visual differences?

Like Photoshop’s High Pass filter, Viveza’s Structure provides a single slider but offers more options with the inclusion of negative values for soft focus effects. In contrast to High Pass, Structure enhances contours with a line that is not as pronounced as Unsharp Mask (Structure is almost incapable of producing artificially hard contouring.) and thinner than High Pass (Structure can’t be used for enhancing planar contrast like high values of High Pass.). Structure accentuates texture somewhat, which can enhance noise as well as detail, but not as much as Unsharp Mask. When Structure is applied, luminosity contrast increases, more so in shadows than in highlights where very high values stop just short of compromising shadow detail. Think of Structure as occupying the visual territory that lies between Unsharp Mask and High Pass.

Color Efex Pro’s Tonal Contrast offers the most control with four sliders; Highlight Contrast, Midtone Contrast, Shadow Contrast, and Saturation. Tonal Contrast is less like Photoshop’s Unsharp Mask and more like High Pass with a touch of Shadows/Highlights thrown in for good measure. Particularly excellent at enhancing highlight detail, Tonal Contrast can go far beyond Photoshop’s Shadows/Highlights and produces more contour targeted effects similar to NIK’s Structure. If used aggressively Shadow Contrast can run the risk of obscuring shadow detail. Highlight Contrast and Midtone Contrast accentuate noise far less than Structure, but this is not true of Shadow Contrast. Tonal Contrast’s greatest strength is its ability to target specific ranges of tone with only lesser effects in adjacent tonal ranges. In the final analysis, Tonal Contrast produces detail enhancement effects that are similar in many ways to processing files with HDR algorithms.

NIK’s algorithms are different than Photoshop’s the so they produce a different look and feel. What could be more important in creative sharpening? Add NIK’s effects to Photoshop’s Unsharp Mask and High Pass and you can choose to play detail in your images with a solo, duet, trio or quartet.

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Output Sharpening

March 29, 2012 | Leave a Comment |

Image source, frequency of detail, subject, personal preference, output device, substrate or presentation device, and presentation size all play a role in sharpening. The art of sharpening gives you precise control over various image characteristics—contrast, saturation, contour (halo and line), texture and noise. It’s best applied in three stages: capture, creative and output.

While there’s an art to sharpening, which provides extraordinary creative freedoms, some aspects of sharpening are best automated, such as output sharpening.

Output sharpening is used to compensate for the softening of detail that a specific device produces. Ink on paper, whether applied with an offset press or an inkjet printer, is notably susceptible to this. When drops of ink hit paper, they deform on impact and spread more or less based on the absorption characteristics of the substrate. This is called dot gain; the dots gain size. Dot gain varies with the type of printer, ink and substrate used. It also can be impacted by environmental factors such as humidity. Output sharpening typically also factors in file resolution and the scale of the final product, which is used to determine an ideal viewing distance—though the actual viewing distance is usually variable.

Output sharpening primarily benefits printed images. Projected images also can benefit somewhat. Images displayed on monitors rarely need to be sharpened for output, as they’ve already been sharpened based on the display device, during capture and creative sharpening.

There’s always a mismatch between the quality of image detail when displayed on a monitor and when printed. Comparatively low-resolution monitors can’t precisely preview what a print will look like on a high-resolution output device, much less precisely preview detail on many different output devices, with varying resolutions or on a variety of substrates with varying amounts of dot gain. So, the image on screen only can approximate, but not precisely display, the sharpness of the printed piece. (In the future, we expect algorithms to be devised to simulate this on screen.) In the end, you make the image on screen look too sharp, knowing it will soften when printed. How sharp do you make it? It depends on your printed proofs. You have to test various sharpening settings, make test prints and compare the results to determine optimum sharpening routines for a given printer and substrate combination. In addition, you should factor in the scale of the final printed piece.

Once determined, the settings used to achieve optimum results in a representative image or selection of images then can be used for all images printed with the same output conditions. You can write an Action to perform an optimum sharpening routine repeatedly. In short, after some initial testing, output sharpening can be automated.

Output sharpening can be complex and tedious. Most photographers would do well to enlist help from the experts to get the job done. There are many competing solutions for output sharpening; automate it in Lightroom or automate it in Photoshop with plug-ins like Nik Sharpener Pro or PixelGenius PhotoKit Sharpener or your own Actions. Using a preexisting solution reduces the testing necessary to create your own settings and brings to bear the considerable knowledge of experts in the field to your prints. Though each of these solutions requires a little testing before implementing, any one of them delivers better results than not performing output sharpening.

Pixel Genius’ PhotoKit Sharpener

NIK’s Sharpener Pro

Lightroom 4 Print Module

Until there’s a truly objective way of determining output sharpening, you’ll have to do a little testing yourself, but the amount of testing you’ll need to do will be minimal when you use automated solutions. Why do automated solutions require a little testing? Because individuals, no matter how objective they try to be, have preferences for image sharpening characteristics, which may or may not mirror your own preferences. They have to make judgment calls and so will you. But when testing their solutions, your task is much easier. You simply raise or lower the opacity of the sharpening layers their routines create, make test prints, determine your preferred opacity, and use that setting for all of your prints. (In Lightroom, you test the four settings: None, Low, Medium and High.)

Output sharpening is the second to last thing you do to enhance an image file before printing it. As a final step, you’ll probably want to carefully inspect an image at 100% magnification to make sure sharpening hasn’t accentuated any minor flaws. If it has, retouch them. And print.

Almost all images can benefit from output sharpening. (Notable exceptions are images with extremely smooth or low-frequency detail, such as minimalist soft-focus fields.) With a little testing, you can determine optimum output sharpening routines for your images and taste, and automate the process, saving you time and delivering better and more consistent results.

What do I use for output sharpening most often? Lightroom.

You can find the do-it-yourself output sharpening routine I recommend on Digital Photo Pro.

Find more sharpening resources here.

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If you know what to look for, you’ll know what path to choose and how far down it to go.

Identifying and developing a sensitivity for the artifacts digital sharpening produces will help you choose a sharpening method and what settings to use during any stage of your sharpening workflow.

You can easily see the artifacts digital sharpening produces by overdoing it.

Here are the seven most common digital sharpening artifacts.

1         Noise

2         Exaggerated Texture

3         Visible Light Halos

4         Visible Dark Lines

5         Loss of Highlight Detail

6         Loss of Shadow Detail

7         Increased Saturation

Each of these artifacts can be reduced in one or more ways.

Here’s a list of options.

1         Noise

Mask areas; consider an edge mask.

Raise Unsharp Mask’s Threshold.

Use High Pass sharpening.

2        Exaggerated Texture

Mask areas; consider an edge mask.

Reduce Unsharp Mask’s Amount.

Use High Pass sharpening.

Filter the High Pass layer with blur or noise reduction.

3       Visible Light Halos

Reduce Unsharp Mask’s Radius to thin.

Reduce Unsharp Mask’s Amount to darken.

Use High Pass sharpening for more feathered contour accentuation.

4        Visible Dark Lines

Reduce Unsharp Mask’s Radius to thin.

Reduce Unsharp Mask’s Amount to lighten.

Use High Pass sharpening for more feathered contour accentuation.

5         Loss of Highlight Detail

Use the Blend If sliders in Layer Styles to recover it.

Mask the highlights only.

6        Loss of Shadow Detail

Use the Blend If sliders in Layer Styles to recover it.

Mask the shadows only.

7         Increased Saturation

Change the blend mode of the filter or sharpening layer to Luminosity.

Desaturate High Pass layers.

Training your eye for what to look for and understanding the upper limits of what other people find to be naturalistic, or at least not distracting, is the first step to developing your unique sharpening style. The second step is knowing what tools are at your disposal and how to use them. Once you’ve taken these steps, you can take the third and final step, knowledgeably putting craft in the service of your vision to make interesting visual statements.

Read more about digital sharpening here.

Learn more in my digital photography and digital printing workshops.

Digital sharpening produces its affects by accentuating contrast, both of texture and of contour. The accentuation of contrast along contours is produced by creating both a dark line and a light halo. While the filters used to sharpen images, such as Unsharp Mask or High Pass, don’t offer independent control of the light and dark components of a contour, you can control them separately using layers. It will take two layers to separate halo from line; one for the halo and one for the line. Filter the two layers differently to produce different thicknesses (Radius) and intensities (Amount) of halos/lines. Then, you can use the Blend If sliders of layers to specifically target either high or low values by moving either the shadows (black triangle) or highlights (white triangle) sliders of This Layer, making those values no longer visible. Some people like to set the Opacity of these two layers to 50% before filtration, so that they can conveniently readjust the intensity of the affect, moving the opacity slider up to make it stronger or down to make it weaker. If you do this too, remember that only the filter’s Radius setting can adjust the thickness of the contours it produces.

Take these steps to make layers that affect halo and line separately.

1       Duplicate the Background Layer to create a Halo layer.

2       Move the Blend If sliders (activate the by double clicking on the layer in the Layers palette) of This Layer to 55 and 75 (hold the option key to split the sliders), disabling the layer’s ability to affect lower values.

3       Sharpen the layer, paying particular attention to the halo.

4       If necessary, readjust the Blend If sliders.

5       Repeat with variation.

6       Duplicate the Background Layer to create a Line layer.

7       Move the Blend If sliders (activate the by double clicking on the layer in the Layers palette) of This Layer to 180 and 200 (hold the option key to split the sliders), disabling the layer’s ability to affect lower values.

8       Sharpen the layer, paying particular attention to the Line.

9       If necessary, readjust the Blend If sliders.

1 No creative sharpening.

2  Halo and line accentuated

3 Halo only accentuated

4 Blend If sliders used to reveal only halo

5 Layer stack for independent halo and line control

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Edge masks target only the contours in an image. (Think of edge masks in Photoshop as the creative sharpening equivalent to the Masking slider in ACR or Lightroom’s capture sharpening.) They keep smooth areas smooth, while accentuating the contrast/sharpness of contours. They can be particularly useful for images that contain moderate to significant amounts of noise. In many cases, they allow the use of more aggressive applications of sharpening effects. Edge masks can help you take all of the creative sharpening effects you design up a notch – or two.

Take these steps to make an edge mask.

1 Full color image

2 In the Channels palette, target the channel with the greatest edge contrast.

3 Duplicate it – using the submenu in the Channels palette to select Duplicate Channel.

4 Filter the new alphachannel with Find Edges – Filter: Stylize: Find Edges.

5 Invert it – Command/Control I.

6 Filter it with Maximum – Filter: Other: Maximum. (Start with Radius of 2.)

7 Filter it with Median – Filter: Noise: Median. (Use the same Radius.)

8 Filter it with Gaussian Blur – Filter: Blur: Gaussian Blur. (Use the same Radius.)

9 Use Curves to increase the contrast and eliminate most of the mid-tones.

10 Use a black brush to paint out any textured areas still visible avoiding contours.

11 Command/Control click on the alphachannel to load it as a selection.
12 In the Layer palette, go to the layer you want to mask and click the Add layer mask icon.

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No High Pass sharpening

Low Radius High Pass sharpening

High Radius High Pass sharpening

There are three methods of sharpening in Photoshop that we should all be aware of: Luminance, Edge and High Pass sharpening. In this order, the three methods become progressively more complex and go to greater lengths to reduce the accentuation of noise.

To minimize the accentuation of noise, Luminance sharpening requires that the Unsharp Mask’s Threshold value be set precisely. When this isn’t enough, Edge sharpening adds a mask that targets the contours of an image, allowing more aggressive sharpening with fewer side effects. Like Edge sharpening, High Pass sharpening (named for the filter used to produce the effect) targets contours in an image, but it does so without the need for a mask. Unlike Edge sharpening, the contour accentuation it produces is soft, feathered and wide. The effect is substantially different and can be used for many creative effects. High Pass sharpening is very similar to the effects of ACR and Lightroom’s Clarity slider, but it offers more control and more varied effects.

Follow these steps to apply High Pass sharpening:

1.?Duplicate the layer that’s to be sharpened.

2.?Change the mode of the duplicate layer to Overlay. This is what generates the contrast effect.

3.?Filter the duplicate layer and apply the High Pass filter (Filter > Other > High Pass) using a Radius setting that accentuates edge contrast without producing halos. This gives the image layer a gray and linear appearance, concentrating the contrast on contours.

4.?Desaturate the filtered layer. Higher Radius settings leave more residual color, and you can get considerable saturation shifts.

5.?Double-click the layer and use the Blend If sliders to remove the effect from near black and/or near white values. Start by moving the This Layer highlight slider to 235, holding the Option/Alt key and splitting the left side of the slider to 215; finish by moving the This Layer shadow slider to 25, and holding the Option/Alt key, split the right half of the slider to 45.

6.?Optionally, reduce the layer’s opacity and/or mask it as desired.

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Sharpening With Layers

November 22, 2011 | Leave a Comment |

There are many reasons to use layers when sharpening your digital images.

Layers can be used to eliminate saturation shifts. Change the Blend Mode of a sharpening layer from Normal to Luminosity. Color noise will be reduced this way.

Layers can be used to prevent clipping in deep shadow detail (near-black) and bright highlight detail (near-white). As sharpening is a contrast effect, near-white and near-black values can be driven to pure white and pure black by it. There’s a cure. Double-click the layer to activate Layer Styles. Use the Blend If sliders to reveal the lost highlight and shadow detail in the background layer below the sharpening layer; zoom way into a highlight area, hold the Option/Alt key and drag the right arrow to restore highlights and the left arrow to restore shadows.

Layers can be masked for greater control over confined areas in an image. To begin, add a layer mask. Select an area from which you wish to remove a sharpening effect, like a sky or other area of even tone, and fill the area with black. You can use this strategy to remove unwanted texture or noise from selected areas of an image. Gray values can be created on a mask with the Gradient tool or with a Brush tool to gradually reduce a sharpening effect. This often can produce a more strongly felt impression of space within an image. In anticipation of selectively modifying an effect, you may decide to sharpen an image more aggressively.

One approach to gaining additional flexibility …

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Unsharp Mask

September 5, 2011 | 2 Comments |

Precise sharpening can improve almost any image. It helps to know when to apply it, what type of sharpening to apply, how to apply it and where to apply it. Forget the filters Sharpen, Sharpen More and Sharpen Edges. They’re just default settings of Unsharp Mask. Even Smart Sharpen offers few advantages over Unsharp Mask; it’s particularly useful for compensating for trace, but not substantial, amounts of motion blur. My advice? Start with the classic and master it.

Why is a filter that makes images appear sharper called Unsharp Mask? In silver-halide-based photography, unsharp masks are made with out-of-focus negatives that are registered with an original positive image. During exposure, the blurring adds contrast around contours, making images appear sharper. Digital unsharp mask works the same way; it uses blurring algorithms to add contrast to contours, again making images appear sharper.

What are the ideal settings for Photoshop’s Unsharp Mask filter? There are no ideal settings that will accommodate all images—or image makers. Settings will be influenced by resolution, ISO, subject and practitioner. As creative sharpening is primarily an aesthetic decision, individuals are likely to prefer different amounts and types of image sharpness. When it comes to the effects Unsharp Mask generates, there’s a general range of believability most viewers share, but whether you play it safe or push the envelope is entirely up to you. You can craft your own sharpening style. To do this, you have to know how the tool works and what to look for.

What are the controls Unsharp Mask offers? Unsharp Mask offers only three controls: Amount, Radius and Threshold. What do they do? Amount controls contrast; a higher setting will create a brighter halo, darker line and contrastier texture. Radius controls how thick halos and lines get. Threshold suppresses the effect in adjacent pixels, based on their relative luminosity; with a very low setting, only adjacent pixels that are very close in color will be affected; with a very high setting, many more color values will be affected.

It’s one thing to hear this. It’s another to see it. To test the filter for yourself, take these six easy steps.

1. Apply the filter to an image containing a range of textures; set all three sliders to their lowest settings.

2. Raise the Amount all the way to 500%. Nothing will happen because it’s not the effect; it modifies the effect.

3. Raise the Threshold all the way to 255; then return it to 0. Nothing will happen because it’s not the effect; it modifies the effect.

4. Raise Radius. You’ll see a dramatic change in your image. What will you see? Bright lines (halos) and dark lines (lines) will appear and grow thicker. Texture will increase. Contrast will increase, particularly around contours and with respect to texture, which may make luminance noise more pronounced. Saturation will increase; color noise may begin to appear.

5. Now move the Amount slider back and forth; you’ll see the halos and lines increasing and decreasing in contrast.

6. Move the Threshold slider back and forth; you’ll see the effect dropped out of a varying range of adjacent values.

While you’re sharpening, keep an eye on these image elements: contours or halos and lines (hard or soft, thick or thin); texture; noise (light/dark or color); contrast; and saturation.

Now that you know how the filter works, how to control it and what to look for, what effects should you consider? There are two primary ways to apply Unsharp Mask: use a low Radius or use a high Radius.

Low Radius applications of Unsharp Mask strengthen the contrast of contours more than their thickness and often can accentuate texture aggressively, for better or for worse. Start with an Amount of 500%. Raise the Radius until it produces an effect that’s unnaturally contoured and textured, then pull back slightly. Reduce the Amount to subdue the effect somewhat until the effect seems convincing. Use a minimum Threshold setting or else the effect may be suppressed unnecessarily and sometimes unnaturally. The idea behind this classic effect is to create a very intense line for maximum effect and to make it very thin so the eye can barely resolve it. Use a maximum Amount, a very precise Radius and a minimum Threshold. When using this effect on high-resolution files, because there are more pixels in a high-resolution image, Radius settings will be higher, you’ll be able to set them more precisely, and you’ll be able to use higher amounts. Higher-resolution files can be sharpened more precisely.

High Radius applications of Unsharp Mask strengthen the thickness of contours more than their contrast and don’t accentuate texture aggressively. Start with an Amount of 100%. Raise the Radius until it produces an effect that’s unnaturally contoured and textured, then pull back until the effect seems convincing. Use a minimum Threshold setting or else the effect may be suppressed unnecessarily and sometimes unnaturally. High Radius effects are often less aggressive or dramatic than low Radius effects. For this reason, they’re often combined together in multi-pass sharpening routines.

You can sharpen an image multiple times and achieve a different effect than sharpening an image only once. How? First apply one type of sharpening and then the other. Typically, high Radius settings are used before low Radius settings, taking care not to create sharpening artifacts in the first pass that will be accentuated adversely in the second pass.

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