Today’s Question: I am one of those who apply sharpening after resizing at the end of the editing process. As I have read lately, sharpening is a process (as opposed to one-time pass). Would you please write about your experience in this respect?
Tim’s Quick Answer: The key advantage of a multiple pass sharpening workflow is that you are first compensating for slight softness in the original capture, and then compensating for the final output. The second step is especially important for images that will be printed, and that sharpening should be applied based on the final output size. But rest assured that it is also possible to get excellent results with a single application of sharpening based on the final output size for the image.
More Detail: When you apply sharpening in more than one pass, you are able to focus each stage of sharpening based on specific goals. As noted above, the first stage of sharpening would be applied to the original image at the original pixel dimensions. This sharpening is intended to compensate for the various factors that reduce sharpness in the original capture.
For example, if your camera includes an anti-aliasing filter in front of the sensor (which most cameras do include) then the image will be slightly softened. Sharpening to compensate for the various factors that impact the sharpness of the original capture would be a very modest application of sharpening.
Some photographers also like to apply a “creative” application of sharpening as a second step of their workflow. This application of sharpening would also be applied at the full resolution of the image, and is aimed at drawing out detail or adding a creative effect to the photo. I think it would be perfectly fair, for example, to think of the Clarity adjustment available in Lightroom and Adobe Camera Raw as a type of creative sharpening effect.
Finally, you want to apply sharpening to compensate for the final output. The best example here would be preparing a photo to be printed. When the ink in a photo inkjet printer comes in contact with the paper, for example, that ink will spread out to some extent. This issue is generally referred to as “dot gain”, and it is especially significant with uncoated matte papers.
Sharpening to prepare an image to be printed or otherwise shared should be applied based on the final output size of the image. This stage of sharpening may need to be applied at a strength that makes the image appear to be over-sharpened, in order to adequately compensate for issues in the final print. Images shared online would need much less sharpening than an image being printed.
It is possible to achieve excellent results for a photo by using a single application of sharpening at the final stage of preparing the image to be shared. That said, you can achieve some benefits in terms of overall sharpness and detail in a photo by focusing specific sharpening stages on specific goals related to optimizing the appearance of a photo.