Memos From The Digital Darkroom

When I sit down with a new client, I ask them a series of questions that are designed to help me understand their level of workflow skills and knowledge. I’m often amazed at how often people who seem to be Photoshop savvy seem to get sharpening wrong. I ran into this twice last week so I thought a blog on the subject would be appropriate.

What is Sharpening?

Sharpening is one of those things that has mystified countless digital photographers. That’s because we expect our images to be in sharp focus, especially when using high quality lenses. However, due to the nature of how digital information is captured, some level of sharpening must be applied to digital photo files captured with a scanner or digital camera.The problem is that there are three different times when it’s appropriate to sharpen a photo. Each of these times has it’s own rules and procedures. If you get them wrong, you could be seriously damaging your images.

Local contrast adjustment when sharpening creates "sharpening halos" around edges with high contrast.

Photoshop and Lightroom’s sharpening filters  are designed to find the edges that surround image details and then increase contrast to pixels along those edges. This is done by lightening one side of the edge and darkening the other. This in effect creates what are called “sharpening halos”, shown in the figure on the left. How these filters are used is beyond the scope of this article. I’ll be covering them in an upcoming article. For now, just remember that the point of sharpening is to trick our eyes into seeing details as sharper by increasing” local contrast” around edges.

Three Kinds of Sharpening

Many photographers are tempted to apply sharpening as soon as they open a photo into Photoshop. It’s a natural tendency because we want our photos to be as sharp as possible. It’s okay to add some “capture sharpening” to a file early in the post-production process. However, when it comes to sharpening, the main event should come at the end of the workflow after the file has been sized for a specific output. In fact, if you’re serious about your photos, sharpening should be used in a specific way at three different times during the workflow.

Capture Sharpening:

The Sharpening portion of Lightroom's Detail panel

Capture Sharpening is used to compensate for the nature of digital capture. It’s used at the beginning of the workflow to bring a file up to snuff. If you’re shooting JPEG files, then the sharpening setting in your camera determines the level of capture sharpening. Because this sharpening can’t be undone, I suggest that when shooting JPEG that you set your camera’s sharpening to its lowest level. That’s because you’ll most likely be adding additional sharpening later.

If you shoot raw, then no matter what your camera is set to, no sharpening is applied to the file during capture. Capture sharpening is applied during the raw conversion. The figure on the right shows the Sharpening section of Lightroom’s Detail panel. Photoshop’s Adobe Camera Raw has a similar panel with the same sliders. The usage of these sliders is discussed in an upcoming article. However, if you’ve used these sliders and the sliders in Photoshop’s Unsharp Mask or Smart Sharpen filters, then you know that these sliders have a much smaller effect on the image. That’s because they aren’t intended to do heavy sharpening.

After the JPEG or raw file is open in Photoshop, additional capture sharpening should not be applied. That’s because any sharpening done at this early stage in the process can negatively affect the outcome of other sharpening that’s applied later in the workflow.

Creative Sharpening:

Creative Sharpening is used during the middle of the workflow to creatively enhance a photo by making a portion of the photo sharper than another. An example of creative sharpening is when a sharpening is applied to the eyes in a portrait. Another way that creative sharpening is used is when a portion of a background is blurred to make the main subject stand out from it. That’s right, blurring can be considered creative sharpening because it causes something to appear sharper. This is a useful technique when you’re dealing with an image that has marginal focus.

Output Sharpening:

Output Sharpening is the final sharpening that’s applied to a file before it’s printed. The amount of sharpening at this point varies with the size of the print - as well as the type of printer and paper being used. For example, if I’m sizing a file for a 16×20, I’ll need to give it a lot more sharpening that the same file that’s sized for an 8×10. If one of these prints is being being printed on an inkjet with glossy paper, I can give it more sharpening than would be appropriate for watercolor paper on the same printer due to the absorbency of the fine-art paper. Printing at a lab may require a different scenario altogether. The point is that I can’ apply final sharpening until I know the final size and output scenario for the print. In some cases I may have a variety of output files for a particular photo that all received different sharpening treatments.

The Bottom Line

Capture Sharpening is used to bring a photo’s oveall sharpness into line. It’s a useful tool, but be aware that you need to apply sharpening again when it comes time to output a file. If overdone early in the process, it may make it difficult to get decent output sharpening without creating unwanted artifacts. The same is true for Creative Sharpening. It’s an extremely useful tool that allows you to guide the viewer’s eye through a photo. However, keep in mind that the main event is at the end of the workflow. That’s when you get to add one of the most important final steps to your photo that brings it into final focus.