This article discusses an image sharpening strategy found in Lightroom but also uses illustrations that highlight the importance of applying image sharpening in a selective manner when necessary. This Lightroom feature is a staple in my image processing workflow! 

The basis of this Lightroom sharpening strategy is to ensure that you apply sharpening only to targeted areas of an image and avoid sharpening areas of an image that contain noise, grain, or otherwise undesirable textures that should not be sharpened or accentuated otherwise. When people view your images, their eye will be attracted to sharp edges and areas of higher contrast. The last thing you want is to accentuate noise/grain, and add contrast to parts of the image that detract from your primary subject. Lightroom gives us an awesome feature in the Masking slider that allows us to literally see the areas of an image that is being targeted for sharpening.

Fig A: Click to enlarge See Figure A: Notice the Detail panel at far right. This is where you’ll find your image sharpening tools including the Masking slider. The Detail panel slider settings you see in Figure A are the Lightroom defaults for raw file conversion. Notice the Masking slider is set to zero. This means that no areas of the image are being masked from sharpening and subsequently the entire image will be sharpened equally. Depending on the image this may be a very bad thing!  

Fig. B: Click to enlarge See Figure B: The magic begins when you hold the ALT key (Option key on Mac) while clicking on the Masking slider. By doing this Lightroom will reveal the “mask” that can be applied to your image and visually shows you what areas will be sharpened and what areas will be masked. The idea of the mask is the same as with any image processing software that uses masks: “black conceals and white reveals”. This means that all black areas of the mask will be concealed (masked off and will not be sharpened), while all white areas of the mask will revealed (no mask applied) and will be sharpened. 

Stop. Pay attention to the noisy/grainy texture in the sky of Figure B. In this particular case the noise/grain is a result of underexposure in that region of the photo. And you will see the same sort of noise/grain from other images that have high ISO noise. In either case, you DO NOT want to sharpen or accentuate these areas of an image. Using the Masking slider will enable you to mask (conceal) these regions and constrict the sharpening mask down to edges that will attract the eye.

See Fig. C and Fig. D below: You will see the Masking slider has been advanced to 20% and 70% respectively. Notice how dramatic of an affect the mask has had on the noisy/grainy sky. At 20% the noise has been significantly reduced and at 73% the noise has been completely masked off. Also compare how the mask constricts down to the edges of the buildings and the moon as the Masking slider advances. These edges are the areas of the image that you DO want to sharpen and accentuate.

Fig. C: Click to enlarge

Fig. D: Click to enlarge

Once you have applied an appropriate mask to your image, release the ALT key (Option key on Mac) and use the Amount, Radius, and Detail sliders to sharpen your image as needed. Although we have masked off a large area of the examples used here, you can still over-sharpen the areas of the image that were visible through the mask. My recommendation is to take it easy … a little dab’ll do ya!

TIP: Holding the ALT key (Option key on Mac) while adjusting the Amount, Radius, and Detail sliders will also reveal a mask that is helpful for evaluating the sharpening effect. 

Note: It is important to recognize that applying the sharpening mask does not remove noise/grain from your images – it only prevents the noise/grain from being accentuated when sharpening is applied. 

Below is Adobe’s definition of the sliders used for image sharpening in Lightroom:

• Amount: Adjusts edge definition. Increase the Amount value to increase sharpening. A value of zero (0) turns off sharpening. In general, set Amount to a lower value for cleaner images. The adjustment locates pixels that differ from surrounding pixels based on the threshold you specify and increases the pixels’ contrast by the amount you specify.

• Radius: Adjusts the size of the details that sharpening is applied to. Photos with very fine details may need a lower radius setting. Photos with larger details may be able to use a larger radius. Using too large a radius generally results in unnatural-looking results.

• Detail: Adjusts how much high-frequency information is sharpened in the image and how much the sharpening process emphasizes edges. Lower settings primarily sharpen edges to remove blurring. Higher values are useful for making the textures in the image more pronounced.

• Masking: Controls an edge mask. With a setting of zero (0), everything in the image receives the same amount of sharpening. With a setting of 100, sharpening is mostly restricted to those areas near the strongest edges.