Today’s Question: Regarding your advice on sharpening, I recently read that expecting/hoping to bring out-of-focus areas into sharp focus is fantasy. The article said sharpening only enhances areas that are in focus. Do you concur?
Tim’s Quick Answer: Yes, I would mostly agree with the overall concept here. Sharpening will not cause an out-of-focus image to appear to be entirely in focus. You can improve the perceived sharpness, including of out-of-focus areas, but that doesn’t not provide the same result as having the image in focus in the first place.
More Detail: I often describe sharpening as enhancing contrast where contrast already exists in an image. This creates the appearance of greater sharpness and detail in the image. You can also think of sharpening as reducing the size of gradations along contrast edges in an image.
Sharpening can dramatically improve the overall appearance of a photo, but there are limits to how much you can achieve with sharpening.
For example, sharpening can help compensate for a photo captured with a lens featuring slightly less resolution than another lens, since the loss of sharpness in this case would be minor.
If a photo is a little bit out of focus, sharpening can help make the image look less blurry, but that sharpening won’t result in an image that will look as good as it would have if the focus was established properly at the time of capture.
If an image is significantly out of focus, sharpening will enable you to change the appearance of the photo, but it certainly won’t produce a photo that appears to have been in focus in the first place.
Similarly, there are techniques for reducing the appearance of motion blur in a photo. But even more than with a photo that is out of focus, with a photo that exhibits motion blur you can’t use a filter to magically get the photo to look like there wasn’t any motion blur. You can get an improvement, but not a perfect result.
So, sharpening can help make up for an image that was captured with less than perfect focus. But if the image clearly has the appearance of being out of focus, sharpening in post-processing is not going to provide a magical solution.