How do I sharpen an image? Seems quite an innocuous question and one to which most new photographers would expect a relatively brief and clear answer.
There is however much more depth to this than many imagine and first we need to be clear what sharpening is and why it is needed.
The camera senor is comprised of discreet cells, millions of them but few come close to the almost 100,000,000 rods and cones in each human eye. The larger we want to print the more evident these initial dots will become in the final print by way of pixellation, soft edges, etc.
My first rule, and it is absolute and unbreakable, is to do ALL sharpening on a new layer;
the reason for this is that sharpening an image boots contrast thereby defining the edges within an image better. It does not as such sharpen anything. Imagine you are looking at a plank of wood that has been rough sawn and you want to sharpen it, the task is easy take a plane or sharp knife and remove the outermost extremities until it is absolutely smooth, now the edges are sharp. Now imagine you are looking at a strand of wool hanging down, you know it has a soft texture made up of a large number of well defined individual fibres. How will you sharpen this? The sharpest knife or scissors will remove the protruding filaments but as soon as you cut into the strand others will be exposed. The relevance of this to a RAW image is that in sharpening nothing
can be cut away when sharpening, the perception of edges can be turned up but at the expenses of something else; you need to find the best compromise.
This is a long article extending to nine pages, to read the rest download the pdf.
and don’t forget to check out the latest article on RAW sharpen for Canon 5D Mk3