SharpeningCompared

Unsharpened / Hybrid / Strong HDR

HDR software is most typically used to render shadow and highlight detail, but it can also 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 mid tones with them. Depending on the HDR software used, a variety of tools are available to restore contrast and separation in mid tones. 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.

For creative sharpening, compare two HDR software packages; Adobe Photoshop and NIK’s HDR Efex Pro.

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Photoshop’s HDR Toning

Adobe’s Photoshop’s HDR solution offers three points of control relevant for sharpening. One, Radius controls the thickness of the halo / line. Two, Strength controls the contrast of the effect. These two sliders are similar to the filter Unsharp Mask but the effect is much closer to the filter High Pass. Three, Detail accentuates texture, with minimal affects on contours. Unlike the filter Unsharp Mask’s Threshold slider, instead of suppressing the side effect of texture accentuation, this slider gives you the ability to control it independently of contour accentuation. (Settings lower than 100% blur the image but not its contours.) Photoshop typically offers the smoothest continuous tone effects.

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HDR Efex Pro

While Google’s HDR Efex Pro presets are rich and wonderful for visually exploring tone mapping variations, for detail enhancement you really only need to focus on two features. First, the Method, which set the base effect; Natural, Clean, Crisp, Halo Reduction, Subtle, Sharp, etc. Second, the Structure slider, which functions very similarly to Viveza’s Structure. 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. Unlike, Viveza’s Structure, the effects on shadows and highlights can be modified with HDR Efex Pro’s Blacks and Whites sliders. Think of Structure as occupying the visual territory that lies between Unsharp Mask and High Pass. HDR Efex Pro’s interface is simple yet more versatile, which means you’ll spend a little more time exploring the many options it offers.

(HDRsoft’s Photomatix is excellent for tone mapping but it is difficult to separate contour and texture from tonal enhancement, making it an overly challenging addition to sharpening solutions.)

If sharpening is your goal, resist the temptation to use the other sliders in each interface; they won’t enhance detail only contrast. That said, much like Photoshop’s simpler TMO Shadows/Highlights they can be used to render shadow and highlight detail more clearly.

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Layer stack for blending multiple renderings

Once images are sharpened with HDR software, the rendered effect can be layered with an unsharpened version of an image, providing more control. Use the blend mode Luminosity to affect only the light and dark values. Use the Opacity slider to reduce the effect. (Knowing you can only reduce the effect, you’ll favor applying the HDR software a little aggressively.) Use the Blend If sliders to remove the effect from either highlights (halos) or shadows (lines) or both. Mask the layer to apply the effect to selected regions. You may even decide to use two (or more) different layers with different HDR treatments to customize effects for specific image regions.

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Before (left) & After (right)

And, of course, sharpening with HDR software can be used in combination with any other sharpening technique, like Unsharp Mask or High Pass filtration.

The options you have for controlling the look and feel of detail in your images are simply unprecedented in the history of the medium. Every digital artist will benefit from exploring these options.

Read more on HDR techniques here.

Learn more in my digital photography and digital printing workshops.

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High frequency

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Medium Frequency

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Low Frequency

Frequency is a term that’s being used more and more. That’s because new tools offer you more control over frequency than ever before. Noise reduction, sharpening, and HDR all offer unprecedented control over the look and feel of detail in our images. Frequency is used to describe the amount of detail packed into a given area of an image. This is measured by the amount of tonal variation between rows or columns of pixels. Imagine measuring an image with a line that passes across it (horizontally from left to right or vertically from top to bottom). The mean or average tonal value along lines can be charted and then compared to values from other measurement lines, especially those nearest to each other.

In high frequency images you’ll find a great deal of variation between measurements; many lines, thick and/or thin, and lots of texture, coarse and/or fine, rendered with high contrast.

In medium frequency images you’ll find a modest amount of variation between measurements; clear contours with moderate to low amounts of texture in between.

In low frequency images you’ll find very little variation between measurements; characterized by smooth long gradations, often with reduced contrast or flat fields of color.

Many images contain a combination of high, medium, and low frequencies. When enhancing images you can choose to emphasize the dominant frequency or selectively enhance areas with different frequencies for even greater precision. Some software features provide ways to target these frequencies as you adjust them. When software doesn’t provide ways to target frequency, you can design an effect for that image area on a separate layer in Photoshop and mask it from other areas you don’t want to be treated in the same way.

In many cases, you don’t need to measure an image to decide what tack to take. By looking at an image with a discerning eye you’ll quickly be able to tell if and where an image contains high, medium, and/or low frequencies.

Simply being aware of and sensitive to frequency in images will encourage you to be more precise with your image adjustments. With a little extra care your images will all become stronger.

Read more about sharpening here.

Learn more in my digital photography and digital printing workshops.

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Of the three stages in a sound sharpening workflow – capture sharpening, creative sharpening, and output sharpening – creative sharpening is the stage that has the most impact.

The goal of creative sharpening is to give an image a specific look and feel. There are at least three things creative sharpening can do for your images. One, creative sharpening can prioritize; it can direct attention to specific areas of an image. Two, creative sharpening can enhance; qualitative aspects of images like texture and line, can be amplified to produce stronger responses. Three, creative sharpening can be used to accentuate different qualities of light; a great deal of detail is carried by the luminosity component of color and changing it changes the overall appearance of light within the image. Used consistently creative sharpening can produce a distinctive style that is more easily recognizable to viewers. (Remember, sharpening is a way to enhance details and it may also be used with its counterpart blurring to make effects appear even stronger by comparison.)

The decisions made during creative sharpening are largely subjective and based on the visual preferences of the individual doing the sharpening, not the characteristics of the tools used to produce an image. When performing creative sharpening there are essentially no rules. Only the image source, the software you choose to use, and, most importantly, your aesthetic sensibilities will determine the limits of how far you can go. If there are limits to how far you should go, those limits are only determined by consensus; in general most viewers don’t want to be distracted unnecessarily by sharpening artifacts – unless they are an integral part of the statement an image makes. During creative sharpening you can leverage any and all sharpening techniques. Creative sharpening can be as simple or as sophisticated as you choose. Increasing your sharpening skills will lead to enhancing your expression. The final determining factor during creative sharpening is that it creates a desired visual appearance.

Creative sharpening needs to be determined visually, while previewing an image on a monitor at 100% screen magnification, the magnification that most precisely displays low frequency detail such as texture and noise.

Creative sharpening is done after Raw conversion that includes conservative capture sharpening, typically in Photoshop, employing additional image layers, with masks. Creative sharpening is most frequently applied selectively, varying the amount and/or type (Clarity, High Pass, Unsharp Mask, Smart Sharpen, etc) of sharpening in different regions of an image.

While there are no standard formulas for creative sharpening that will apply equally well for all images and more importantly all users, this doesn’t mean you can’t automate many parts of creative sharpening, once you’ve created a sharpening recipe that pleases you. Recording your preferred sharpening routines as actions can speed up this process. It does mean that to get it really right you’ll want to modify the results of your recipes based on the characteristics individual images you’re processing – sometimes subtly and sometimes substantially.

Creative sharpening may need to be removed and reapplied if an image file is dramatically upsampled, as the resampling process can make sharpening artifacts not visible at smaller scales more pronounced at larger scales and in some cases exaggerate them.

Not all images need to be creatively sharpened. In high productivity workflows, where large volumes of images need to be processed quickly, creative sharpening is typically abandoned because it can’t be fully automated. But ‘hero’ images are another matter entirely. The images you care most about deserve creative sharpening – and for these it can make all the difference in the world.

Follow up with How To Avoid Common Over-Sharpening Artifacts.

Read more about sharpening here.

Learn more in my digital photography and digital printing workshops.

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Layers have Blend Modes and can be masked

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Double click a layer to activate its Blend If sliders  

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

How do you do this? Simply duplicate the Background layer and sharpen the new layer.

Eliminate Saturation Shifts

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

Prevent Clipping

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.

Precise Local Adjustment

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 with sharpening effects is to set a sharpening layer to 50% Opacity before applying the filter and then later adjust the opacity up or down to get more or less of the effect. This can be useful, but be mindful of its limitations. Reducing or increasing a sharpening layer’s opacity will provide an effect similar to adjusting Amount; more or less contrast is added. But modifying opacity can’t simulate the effects of different Radius settings—thicker or thinner contours.

Combine Multiple Types Of Sharpening

Use more than one duplicate layer and you’ll be able to combine multiple types of sharpening by simply reducing the top layer’s opacity. Unsharp Mask, High Pass, and Clarity all produce different effects that can be combined into still new effects. With these tools, you can craft a unique look and feel for detail in your images.

In addition to the flexibility of changing and/or removing and remaking sharpening effects layers’ features Blend modes, Blend If sliders, Opacity, and Layer Masks offer extraordinary control and precision. When you want to get sharpening effects really right, use layers.

Read more on sharpening here.

Learn more in my digital photography and digital printing workshops.

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Ansel Adams and Imogene Cunningham by Alan Ross

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Adobe Camera Raw’s Detail panel

Optimal image sharpening is best done in three stages – capture (Do it during Raw conversion.), creative (Do it in Photoshop.), and output (Automate it.).

This article covers the first stage of sharpening – capture sharpening.

Capture sharpening benefits all images. Capture sharpening compensates for inherent deficiencies in optical and capture systems. All lenses and sensors have specific characteristics and deficiencies. They do not all have the same characteristics or deficiencies.

To speed your workflow, default settings for a best starting point for capture sharpening can be determined for all images created with the same lens/chip combination and saved for subsequent use. To optimally sharpen an image, you’ll need to modify these settings to factor in additional considerations – variances in noise (ISO, exposure duration, temperature), noise reduction settings, and the frequencies of detail (low/smooth to high/fine texture) in an image.

Capture sharpening is determined visually. Perform capture sharpening while previewing an image on a monitor at 100% screen magnification, the magnification that most precisely displays high frequency detail such as texture and noise.

Capture sharpening is best done during Raw file conversion. (Do it after scanning for analog originals.) I recommend importing your Raw files into Photoshop as Smart Objects. If you do this, you can quickly access specific sharpening and noise reduction settings simply by double clicking the image layer. At the same time, you’ll also be able to take advantage of any updates in detail rendering (noise reduction and sharpening) with the click of a button. (Do be mindful that any adjustments you make in Adobe Camera Raw will not be recorded in a Lightroom library.)

Capture sharpening is typically done globally and uniformly to all areas of an image, but on the fly masking routines are recommended for reducing and removing sharpening effects, such as halos on contours and noise in low frequency or smooth image areas.

When performing capture sharpening, err on the conservative side and avoid producing unwanted artifacts. Don’t fall prey to the temptation to fix unwanted sharpening artifacts you could produce at this first stage of sharpening in subsequent stages of image editing; you’ll get better results if you don’t produce unwanted sharpening artifacts at all. Additional sharpening enhancements can be performed locally with more precision in Photoshop during creative sharpening.

Set Clarity before sharpening. It produces a different but related contour contrast. If you change Clarity settings substantially, double check your sharpening settings

Perform noise reduction before capture sharpening. You’ll use slightly more aggressive sharpening settings to compensate for the blurring noise reduction introduces. As with capture sharpening, produce as few artifacts as possible during noise reduction. If you need to perform more aggressive or localized noise reduction, do it in Photoshop. (See my noise reduction series on digitalphotopro.com.)

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Lightroom’s Detail panel

The Detail controls in Adobe Camera Raw and Lightroom are identical; only their appearance varies.

There four Sharpening sliders.

1          Amount controls the contrast of the effect produced.

2          Radius controls the width of halos (light) and lines (dark) produced around contours.

3          Detail skews the effect towards a particularly frequency of detail – high, medium, or low.

4          Masking creates on-the-fly edge masks, removing the effect from smoother lower contrast areas. (You can see the mask when you hold down the Option/Alt key and click on or slide the slider.)

Images with high frequency detail benefit from using smaller Radius settings, higher Amount and Detail settings. (And lower Noise Reduction settings.) Images with low frequency detail benefit from using higher Radius settings, lower Amount and Detail settings. (And higher Noise Reduction settings.) Images with a wider variety of frequencies, especially those that containing significant contours, benefit from higher Masking settings.

If you don’t know where to start, start with an Amount of 100, a Radius of 1.0, and Detail of 50. Then adjust with the above recommendations in mind, but above all look critically at the way the effect affects your image.

There will be many times when you will want to readjust Noise Reduction settings after determining Sharpening settings. The two are intimately related.

Finding an optimum balance involves making trade-offs. Again, be conservative and avoid producing artifacts. This is perhaps the hardest part of capture sharpening, as the tools are powerful and the effects can be compelling so the temptation to go too far is great. Resist. Remember, there’s a second stage of sharpening for localized effects – creative sharpening.

Double processing Raw files with Photoshop will allow you to apply different noise reduction and sharpening settings to different areas of an image with great precision. In one version you can aggressively sharpen high frequency detail with little noise reduction, such as textured stone, and in second version you can minimally sharpen low frequency detail with high noise reduction, such as a clear blue sky. When you do this, you can optimize sharpening settings for one frequency of detail and ignore the artifacts produced in another. With detail settings optimized for different frequencies on separate layers in Photoshop, you can mask the suboptimal areas in the overlying layer and reveal the optimal detail in the layer below. (Here’s an easy way to do this. First, import the first version into Photoshop as a Smart Object. Second go to Layer : Smart Objects : New Layer Via Copy. Third, double click the new Smart Object to change the detail settings in the overlying layer. Note, if you simply Duplicate a Smart Object instead the settings will be reset in both layers. The way you make the Smart Object determines whether the duplicates share the same settings or have different settings.)

Read more in my digital image Sharpening resources.

Learn more in my digital photography and digital printing workshops.


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