Optimal image sharpening is best done in three stages—capture (do it during RAW conversion), creative (do it in Photoshop) and output (automate it).
Capture sharpening benefits all images. It compensates for inherent deficiencies in optical and capture systems. All lenses and sensors have specific characteristics and deficiencies. They don’t all have the same characteristics or deficiencies.
To speed your workflow, default settings for a best starting point for capture sharpening can be determined for all images created with the same lens/chip combination and saved for subsequent use. To optimally sharpen an image, you’ll need to modify these settings to factor in additional considerations—variances in noise (ISO, exposure duration, temperature), noise-reduction settings and the frequencies of detail (low/smooth to high/fine texture) in an image.
Capture sharpening is determined visually. Perform capture sharpening while previewing an image on a monitor at 100%, the size that most precisely displays high-frequency detail such as texture and noise.
Capture sharpening is best done during RAW file conversion. (Do it after scanning for analog originals.) I recommend importing your RAW files into Photoshop as Smart Objects. If you do this, you quickly can access specific sharpening and noise-reduction settings simply by double-clicking the image layer. At the same time, you’ll also be able to take advantage of any updates in detail rendering (noise reduction and sharpening) with the click of a button.
Capture sharpening is typically done globally and uniformly to all areas of an image, but on-the-fly masking routines are recommended for reducing and removing sharpening effects, such as halos on contours and noise in low-frequency or smooth image areas.
When performing capture sharpening, err on the conservative side and avoid producing unwanted artifacts. Don’t fall prey to the temptation to fix unwanted sharpening artifacts you could produce at this first stage of sharpening in subsequent stages of image editing; you’ll get better results if you don’t produce unwanted sharpening artifacts at all. Additional sharpening enhancements can be performed locally with more precision in Photoshop during creative sharpening.
Set Clarity before sharpening. It produces a different but related contour contrast. If you change Clarity settings substantially, you need to double-check your sharpening settings.
Perform noise reduction before capture sharpening. You’ll use slightly more aggressive sharpening settings to compensate for the blurring noise reduction introduces. As with capture sharpening, produce as few artifacts as possible during noise reduction. If you need to perform more aggressive or localized noise reduction, do it in Photoshop. (See my noise-reduction series)