Understanding Sharpening With Adobe Lightroom

Adobe Lightroom features a wealth of editing tools for the digital photographer, and for anyone concerned about optimizing their images output, understanding the sharpening options is one of the keys to making images sing.

Just like many aspects of Lightroom's RAW editing suite, the sharpening adjustments feature enough simplicity for set-it-and-forget-it batch processing while also giving the user the fine-tuning that allows individual images reach their full potential.

Instead of multiple approaches to sharpening as you might kind in Photoshop, Adobe Photoshop Lightroom takes a different approach with four sliders you can use to optimize your images. Let's take a look at sharpening a single image and how Lightroom's Amount, Radius, Detail, and Masking sliders work.

Amount Slider

The Amount slider is straight forward, controlling the blunt amount of sharpening that's applied to the image. Just as dialing up the volume on your stereo increases the volume, the Amount slider affects how much sharpening is applied.

Without any sharpening applied via the Amount slider, none of the other sliders in the sharpening dialogue are enabled. And while the unsharpened image shows potential, the details lack a sense of crispness that would be desirable for prints and most other applications.

Since sharpening acts by increasing contrast and making the differences between two areas more apparent, the Amount slider controls this application of contrast.

In the above example with a setting of 40 dialed in to the Amount (along with other variables that we'll get to in a moment), the image starts to pop.

Amount Preview:

While the normal image viewer in Lightroom continually updates the preview based on your adjustments, Lightroom offers some handy preview modes that can help discern the finer differences between settings that guide you in sharpening your photos. To enable this preview mode, hold down Option (Mac) or Alt (PC) while adjusting the sliders.

In the Amount preview, you're shown a simple grayscale version of the image so that you can judge sharpening without considering color contrasts.

This display is important because contrasting colors (such as red and green, yellow and blue, etc) can give a false impression of sharpness; by discarding that info, you're able to best judge the sharpening process.

One nice thing about Lightroom is that all of Lightroom's sharpening processes act exclusively on the luminance of the image, so that the color and hue of the image are unaffected by the changes in contrast.

Radius Slider

If the Amount slider affects how much sharpening is applied, the Radius slider controls that sharpening is distributed. The Radius slider determines how far away from edges the sharpening extends, starting at 0.5 pixels up to a maximum of 3.0 pixels.

Just as the size of a paint brush dictates the scale of details one can paint, in this sense, the Radius slider can help set how finely or coarsely details are rendered.

A small Radius is best suited to enhancing the edges of fine details in an image. In the above example, this tight Radius keeps the blades of grass on the bank of the river distinct and renders individual leaves in the larger plants. When using a Radius close to 0.5, you will notice that that the contrast of the image can take on a slightly “airy” feel at the micro level, since the edge/contrast enhancement of sharpening is more tightly applied and affects less of the total pixels in the frame.

A larger Radius setting of 2.5 used on the same image, below, distributes sharpening more widely, causing wider edge contrasts and blurring in the fine details of the grass. Here, sharpening degrades the image information, rather than helping to reveal it.

Radius Preview:

While the preview mode for the Radius slider shows a grayscale image, just like the Amount preview, this preview mode shows the level of edge enhancement, rather than just a grayscale conversion. Again, toggle this preview mode by pressing Option (Mac) or Alt (PC) while you're moving the slider.

In this preview mode, the majority of the scene is rendered as a middle gray, while areas affected by the Radius setting are shown with their edges highlighted by increased contrast.

One image aspect that can inform what Radius you should use is the hierarchy of details you want to highlight. Since the Radius controls the granularity of sharpening, you can emphasize different scales of detail with the radius tool, while effectively reducing others, as we've seen in the fine detail above at a Radius of 0.5.

Detail Slider

The Detail slider adjusts how much high-frequency information in the image is sharpened and how edges are emphasized. The scale runs from a base of 0, at which only major edges are sharpened, to 100, at which even minor edges in the  textures of an image are sharpened.

In my workflow, I generally think of the Detail slider as a continuation of fine-tuning where the Radius slider leaves off, allowing a continued refinement of the granularity of sharpening and allowing you to bring out even more of the finest elements with the proper application.

With a Detail setting of zero, the landscape contains a degree of overall sharpness due to the Amount slider, but still lacks definition in the finest elements. While this might be a negative aspect in a landscape image, a low detail setting like this is ideal for portraiture, as it minimize skin texture and can help focus sharpness on larger features, like the eyes.

In contrast to the way the Radius slider can affect relatively large details in the scene, the Detail slider focuses on the edge enhancement of much finer structures. With a relatively high setting of 70 in the Detail slider, the micro-details of the image really come alive. At these Detail settings, the grasses in the zoom area of the Detail pane and the smaller boulders on the rockface gain some bite, albeit at the expense of sharpening artifacts elsewhere in the frame.

When using higher Detail settings, one has to be careful for moire, jagged edges, and a general look of digital artifacts – all of which can occur as you push images to very high frequency sharpening.

Detail Preview:

The Detail preview mode is similar to that found in Radius, with subtle differences. Overall, both the Radius and Detail preview modes show the edge enhancement on the image, but the Detail preview – as one might expect – offers a finer rendering that shows more attention to the minor edges in the textures of an image.

In this preview of the above scene, with a Detail setting of 70, you can see the definition of edge detail and the finer texture that the sharpening begins to target. Areas like the shadow on the right of the frame don't have much texture, so there's little edge enhancement performed. In contrast, the sun-lit face of the mountain is covered with minute details, which are exactly the kinds of features that are perfect for this enhancement.

As the Detail slider is increased toward higher levels, you'll be able to see an increasing amount of texture being highlighted in the preview, corresponding to the additional sharpening Lightroom is applying to the image.

Masking Slider

The masking feature of Lightroom 3 allows you to selectively apply sharpening based on image content – specifically, edges. With a default Masking setting of zero, the sharpening is applied evenly to the entire image. Turning up the Masking value begins to selectively mask out areas of lower detail, fewer edges, and increasing distance from strong edges.

While Masking allows you to selectively sharpen, the flipside of de-emphasizing detail is equally important. Using Masking, it's possible to leave skintones smooth, minimize digital noise at high ISO, and ensure smooth gradients.

The above image, with lots of deep blue sky, is a great example for the benefits of using the Masking slider to preserve smooth tones in the sky while still allowing the fine details of the dog's fur to pop.

Masking Preview:

With the Masking preview, you're being shown how the overall sharpening scheme – including the Amount, Radius, and Detail – is being applied. Just like a layer mask in Photoshop, Lightroom's sharpening mask is displayed in the same way, where black areas receive no effect and white areas receive the full treatment.

Here in the Masking preview with a setting of 30, the sky is completely masked out in black, which means those areas are not sharpened at all, while the white areas in the fur and other areas of detail still receive the appropriate sharpening treatment. Areas in gray receive partial sharpening based on their proximity to edges and areas of contrast.

For me, this Masking adjustment is one of the huge benefits of using Lightroom and working directly on the RAW images. In my old workflow, I would apply a standard amount of sharpening with my RAW converter, export the image, and then either settle with uniform sharpening (including that of artifacts like noise) or remove them after the fact through more post-processing. With Lightroom 3, you have a turn-key solution that is a tremendous time saver that offers flexibility and great image quality.

Sharpening For Different Subjects

So, why does Adobe bother including different adjustments for sharpening? Simply put, different types of images will require different combinations of settings.

Every image will have different sharpening needs, depending on subject. To get things started, Adobe provides two presets in Lightroom, and analyzing their settings does give some insight into the mechanics of the settings we've already covered above.

Sharpening Preset: Wide Edges

Wide Edges (Faces):

Adobe's portrait preset, which it dubs sharpening for “wide edges,” uses a slightly wide Radius to emphasize larger lines of contrast like those of the eyes. A low Detail setting, together with a high masking amount ensures that this sharpening treatment will be flattering to skintones.

Lightroom Preset: Narrow Edges

Narrow Edges (Scenic):

In contrast, Adobe's “narrow edges” sharpening preset is equally educational. The overall sharpening level is just slightly higher, but now with a much smaller Radius, which, together with a high Detail setting, emphasize small-scale detail to a fine degree. Assuming optimal shooting conditions (and typical landscape settings) with a small aperture to maximize depth of field/detail and a low ISO to minimize noise, zero masking is applied with this preset.

Of course, these presets provided of Adobe are just starting points – every image will have slightly different sharpening  requirements depending on myriad factors like the lighting, camera, ISO, lens, aperture, and scale/distance of the subject relative to the frame.

Next Steps

In the next part of this feature on understanding sharpening in Lightroom, I'll do a step-by-step tutorial on sharpening a sample image and call out some of the factors I consider in the process. In the meantime, now that the four settings of the sharpening dialogue should be a little less mysterious, go out and start cracking on your favorite images.

UPDATE: View the 6 Steps For Sharpening In Lightroom.

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End Notes

Thanks to the ability to fine-tune and dial in just about any imaginable detail, Lightroom's sharpening dialogue is one that works beautifully on any image you throw at it. For images that require individual attention, Lightroom offers intelligent options for squeezing the most out of your RAW files.

Best of all, with Lightroom you're working with the RAW data in a non-destructive, completely reversible manner for the highest image quality, which translates into better sharpening and a smarter workflow.

Get Lightroom

I think that you'll be surprised and pleased by the flexibility of Lightroom's sharpening process. So start playing around – your images will thank you.

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