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 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 tell tale 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.


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01_CaptureSharpen

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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.


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No sharpening.

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Double pass Unsharp Mask sharpening.

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Hybrid Unsharp Mask and High Pass sharpening.

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.

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A low High Pass filter setting.

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A high High Pass filter setting.

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 filter Unsharp Mask’s Threshold setting be set precisely. When this is not 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 after the filter used to produce the effect) targets contours in an image, but it does so without the need for a mask; a mask which is more complex to produce. 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.


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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 analog chemical 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 is 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, base 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.


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When To Sharpen

The vast majority of photographic images benefit from sharpening.

Before you decide how and when to sharpen images, you need to decide why you’re sharpening them.

The goal of sharpening is to enhance detail rendition without producing distracting visual artifacts.

You’ll find many conflicting philosophies and their accompanying strategies for sharpening images. The seemingly conflicting advice can be hard to reconcile.

Should you sharpen once or multiple times? Should you sharpen differently for different subjects? Should you sharpen differently for different sizes? Should you sharpen differently for different presentation material or supplies? Should you view your files at 100% or 50% screen magnification?

Capture source, output device, substrate or presentation device, presentation size, subject, and artistic intention all play a role in sharpening. The characteristics and solutions for many of these factors can be objectively defined for everyone; at least one of these factors, perhaps the most important, your artistic vision, can only be decided individually.

So, if sharpening is a complex subject, how do you simplify your sharpening workflow to one that’s practical without compromising quality?

Bruce Fraser and Jeff Schewe offer the best advice in their definitive volume on sharpening, Real World Image Sharpening, which I highly recommend you read. Instead of sharpening your images for you, they teach you how to sharpen.

Their philosophy of sharpening is the soundest in the industry, which is why it has been adopted by so many in the industry. They recommend that images be sharpened in a progression of three stages; once for capture sharpening, a second time for creative sharpening, and a third and final time for output sharpening. The objectives and methods of each of these stages vary considerably. When mastered, the whole process can be streamlined to achieve sophisticated results with a minimum investment of time.

Here's a quick synopsis ...

Read more on Creative Image Sharpening here.

Learn more in my Digital Printing and Digital Photography Workshops.


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