Tuesday, 11 April 2017

sharpness - Why should my last post-processing step be sharpening?


I've seen a number of people recommend that you apply sharpening as the last step in post-processing, and some seem to imply you should always do that.


Why? I tend to discard pictures that either are not tack sharp at the focus point, or at least good enough that I don't mind. If I think the result looks good enough, even at 100%, why would I want to apply sharpening, and why should it be the last step performed?



Answer



First of all, sharpening isn't (at least primarily) to compensate for pictures that weren't sharp -- it's primarily to reverse (or least ameliorate) the effects of interpolation that's inherent in converting the data from a typical Bayer-pattern sensor into a recognizable image.



There's also (at least typically) interpolation done when you resize an image. To compensate for that interpolation, you need to do the sharpening after the interpolation -- but you want to keep the image full size for as much post-processing a possible to maintain maximum quality in your editing. Therefore, you want to do all the other editing, then size the picture for the target, then do a final sharpening step to compensate for the interpolation in the sizing.


You might also want to read Patrick Lavioe's paper on sharpening in three steps.


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