Sharpen algorithms trade gradiation for "edge effects" (as we used to call it).
One can always tell where they've been applied.

Gradiation is really important -- its one of the measures of image quality.
You don't want your lanscape to end up looking like somebody drew
over it with a sharp pencil. That's phony sharpness.

Like a plaster cast on a leg, sharpen has its uses---but probably only as a last
resort. We shouldn't go out planning to break a leg or to take unsharp
images!

A sharp image contains more information than a fuzzy image.
Missing information about a scene cannot be created out of nothing.
If you use shapen, it will look shaper--but at a price.

Sharpen is not reversible: there is no "put it back the way it was".
That's because sharpen algrorithms lose information. Areas of
gradually changing tone are being traded for a sharp edge. All that
beautiful gradiation is sacrificed.

Unfortunately, image processing software packages like Photo Shop
don't bother to tell the user which digital filters are information-lossy.
(They know *exactly* what I'm talking about.)

In general, there is no "free lunch" in photography: if you screw up a
shot, there is no way to magically fix it (some color correction and
minor lightening and darkening excepted). To improve one thing,
you have to sacrifice something else. Come to think of it, that's a
lot like life....

Relying on sharpen is one of the *worst* habits in digital photography.

Sharpen algorithms trade gradiation for "edge effects" (as we used to call it).
One can always tell where they've been applied.

Gradiation is really important -- its one of the measures of image quality.
You don't want your lanscape to end up looking like somebody drew
over it with a sharp pencil. That's phony sharpness.

Like a plaster cast on a leg, sharpen has its uses---but probably only as a last
resort. We shouldn't go out planning to break a leg or to take unsharp
images!

A sharp image contains more information than a fuzzy image.
Missing information about a scene cannot be created out of nothing.
If you use shapen, it will look shaper--but at a price.

Sharpen is not reversible: there is no "put it back the way it was".
That's because sharpen algrorithms lose information. Areas of
gradually changing tone are being traded for a sharp edge. All that
beautiful gradiation is sacrificed.

Unfortunately, image processing software packages like Photo Shop
don't bother to tell the user which digital filters are information-lossy.
(They know *exactly* what I'm talking about.)

In general, there is no "free lunch" in photography: if you screw up a
shot, there is no way to magically fix it (some color correction and
minor lightening and darkening excepted). To improve one thing,
you have to sacrifice something else. Come to think of it, that's a
lot like life....

Relying on sharpen is one of the *worst* habits in digital photography.