Sharpening is almost always necessary for digital images – whether they were produced with a digital camera or from scanned film or prints. Several aspects influence the sharpness of an image, ranging from lens quality, to weather conditions, to the in-camera processing method, so some software sharpening is required for images to look their best. There are options for sharpening at the RAW stage, in Adobe Camera Raw, Lightroom or Capture, as well as multiple tools in Photoshop. For quality prints, it is often necessary to sharpen twice – once in RAW and then again before print, as this compensates for any loss of fine detail caused by the surface or the print media. Here we analyse the key sharpening options and why may choose to use them.
Camera Raw/Lightroom
Camera Raw and Adobe Lightroom share many processing features and the Sharpening Panel is one of these. The interface in these applications is very simple yet sophisticated, with the major shared advantage being that of non-destructive editing. Any settings applied here can be revised at any time, before moving into Photoshop. There are very useful options for minimising noise caused by sharpening and limiting sharpening to key areas, using Masking. Handily, Noise Reduction shares the same tab, so this can be tailored, based on the level of sharpening required. There is the disadvantage of being limited to global effects, rather than highly local changes, made possible with layer masks in Photoshop, however this can be remedied by applying sharpening through the Adjustment Brush. This should be considered a default step in most photography workflows.
Unsharp Mask
A long-time favourite tool in Photoshop, Unsharp Mask (Filter > Sharpen > Unsharp Mask) is a reliable method of sharpening your images. It is also fairly simple and intuitive to use, consisting of only 3 main sliders. The Amount controls the strength of the effect, Radius dictates how obvious the sharpening is around edges within the photo and Threshold influences which tones are affected (how much contrast two adjacent pixels must have to be considered an ‘edge’). The quality of the sharpening is consistently good if used in moderation and is the pro choice for general purposes. This tool gives the impression of being in full control of the effect and settings can be pushed quite far without unexpected pixelation effects.
High Pass
This technique is great when there is quite significant blur in certain areas of the photo, or when you want to create a grungy, high-detail effect (it is a useful detail extractor.) It is also quite a dynamic tool, since the strength of the effect can be controlled in-part by the blend mode of the layer to which it has been applied. To use the filter go Filter > Other > High Pass, choose a Radius (select a lower value for small, fine detail) and click Ok. Apply this on a duplicate layer and change the blend mode to Soft Light for everyday sharpening or Overlay for a more pronounced impact. This option tends to enhance noise quite a bit, although flat tones can be masked out using a layer mask. It is quick and relatively simple to use, although it can introduce severe halos if over-used.
Sharpen Tool
This is the tool to use for very local sharpening, where small parts of an image need significantly more sharpening than the surrounding areas. A typical situation where this tool would be used is when editing a portrait shot and the eyes require some lifting. Using the Sharpen Tool at around 10-20% and gently brushing over these elements, small-scale contrast and detail can be revealed, adding depth to your shot. This tool is easy to implement, but doing so correctly takes practise. It is very easy to over-do the sharpening and when this occurs, several pixelation can result. It is not a tool to use over large, regional areas, as this can produce uneven effects, which are highly noticeable.
