The Three Stages of Sharpening

When it comes to post-processing photos, sharpening is one of the most important and potentially destructive steps in the procedure. Almost all images that manage to find their way from the camera to the computer can do with at least a little sharpening and, in the case of RAW files, even a lot of sharpening. The difficulty, though, is that sharpening is easily overdone and can leave photos with a crunchy, phoney look about them. Sharpening also has the added penalty of exaggerating noise and in the worst examples of overdoing it, can introduce other unwelcome image artefacts along high-contrast edges.

The problem is that like most other topics in photography, there is no single approach to the matter of image sharpening that can be universally applied. Each and every photo requires personal attention. A further matter which is often overlooked by novices is that sharpening of portfolio-grade images is seldom done in a single step. An image on the path from camera to print, for example, is likely to pass through the following three sharpening phases before landing up on the wall and the same can be said for photos landing up in a professional online gallery.

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Input Sharpening

As the name so eloquently suggests, input sharpening takes place at the input end of an image processing workflow, typically when said image winds up in Lightroom. It is the very first step in the sharpening process and for many photos the last step too. If a photo is destined for a life as personal memento or perhaps even set to make an appearance in a Facebook newsfeed, then this is as far as the road goes. These sorts of situations don’t require elaborate editing wizardry and the Amount, Radius, Detail and Mask sliders that reside on Lightroom’s Sharpening panel are more than up to the task.

 Lightroom's sharpening tools.

Lightroom's sharpening tools.

The general philosophy when dealing with these less demanding scenarios is to view the photo at a 1:1 magnification and to increase sharpness to the point where the resulting increase in noise exceeds any gains in, well, sharpness. One thing to keep in mind, though, is that not every image benefits from being razor sharp. Some photos look better when imbued with a softer, more ethereal look.

If, by contrast, a picture is earmarked for more detailed adjustments in Photoshop, then input sharpening is just a rudimentary step although no less important. Under these circumstances, the goal is to only increase the sharpness enough that significant edges within the photo are well defined. Such applications of input sharpening are principally aimed at making subsequent Select and Mask operations in Photoshop a little easier. It is critical at this stage to avoid the ever-present temptation to sharpen a photo to the levels that you would expect to see in the finished product. Doing so will only limit what can be done in Photoshop before noise raises its ugly head.

General Sharpening

Once you have made the decision and opened the can of worms that is Photoshop, you have stepped into the realm of general sharpening. In this domain, sharpening is not simply a global adjustment as before, but one that can be applied locally too. Certain parts of an image might benefit from more sharpening than others and by leveraging the power of Photoshop’s Select and Mask tool, as well as other more sophisticated selection techniques, photographers have unmatched control over where and by how much sharpening is applied.

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An example of when one might selectively apply sharpening is when using a mask to avoid sharpening areas of a photo that are in shadow. Noise is always more apparent in the shadow areas of an image and sharpening such areas will only make things worse.

Technically, it is possible to make local sharpening adjustments within Lightroom, avoiding the need for general sharpening altogether; however, there is simply no comparing the amount of control offered by Photoshop with that of Lightroom, it’s a monumental difference.

Output Sharpening

When you have reached the point where you are happy with your editing and the photo is deemed complete, it is time for the final phase, output sharpening. Generally speaking, images that make it to this stage are intended for both the web and print and these two output types each require a unique approach.

To get the most out of a print, the image you send to the printer needs to be slightly oversharpened. One of the inherent characteristics of printed media is that it is softer than its computer-based brethren. To mitigate any loss in image detail, it is prudent to proactively dial in a hint of oversharpening. The amount of oversharpening required by a photo varies considerably based on the printing technology being used as well as the paper. If you have the luxury of producing test prints, then this is the time to use them.

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For web photos, though, there is a good chance that the resolution of the image will have to be reduced before it can be posted. Most websites do best with photos that have a longest edge of between 2000 and 3000 pixels, considerably smaller than what your camera is liable to produce. Downsizing such a photo can be as simple as setting the Image Size parameters in Photoshop and letting the program do its thing; however, reducing a photo dramatically in one step is likely to see a loss in detail.

Instead, to preserve all the information in the image, it is best to complete a series of much smaller size reductions punctuated with incremental increases in sharpness. An example of this method might be reducing the image size by 20%, then increasing sharpness marginally and repeating these steps until such time that the photo reaches the desired dimensions. If this sounds like a tedious process, it is and for this reason, there are several free and paid Photoshop Actions available for download that will do the heavy lifting for you.

Parting Thought

When writing on topics such as this, I am always haunted by the voices of those who argue that “you should be getting it right in camera” as the notion is such a comfortable one. If it were at all possible to “get it right in camera”, it would mean that we can circumvent the hours spent behind the computer agonising over sharpening. However, I can assure you that there are very few – if any – award-winning landscape photos about where the photographer didn’t painstakingly address sharpness at each of the stages mentioned here. At the very least, they would have considered the matter and if you are looking to get the very best from a digital photo, then you have very little choice but to follow suit.

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