Selective sharpening - newbie question

Recently there was a very enlightening but somewhat confusing post to the photo critique forums (see link below).
http://www.naturephotographers.net/imagecritique/ic.cgi?a=vp&pr=60585&b=vg1&st=0&la=890&ph=49&sid=20555&u=20555

I would like to understand, why selective sharpening is performed? Is it done to avoid confusing the background with the subject? To make the subject stand out more from the BG? Or does it have other factors that I am ignorant of?

Can someone adequately explain?

Thanks!

The idea is that you want to sharpen detail in your object but avoid creating halos or sharpening unwanted artifacts (noise/grain).

Rather than selecting the object you want to sharpen, I find it much easier to create a mask over the objects you don't, using either the quickmask tool or something like Tony Kuyper's luminosity masks.

Guy

Hi Bran,

Sorry the discussion wasn't clear. The reason for doing selective sharpening is partly to keep from applying sharpening to background that don't look as good as they do unsharpened because of noise or unnecessary detail. The other reason is that sometimes if you get a subject that is in marked contrast to the background, applying sharpening can cause a halo (which is a sharpening artifact). To avoid these problems you can select only the parts of the image that will actually benefit from the sharpening (hence selective sharpening).

I hope this is of some help.

Br(i)an,

Selective sharpening is typically used to prevent over-sharpening of smooth-toned areas in a scene, e.g. the sky. Smooth-toned areas tend to become quite noisy (grainy looking) if too much sharpening is applied. In the case at hand, the photographer wanted to sharpen the bird to prevent oversharpening of the sky, and also to make the bird 'pop' a bit more. At least, that's how I see it.

I have used selective sharpening to sharpen a mountain against a sky with clouds. I did this so that the blue sky would not be grainy-looking and so the clouds looked nice and smooth while the mountain was tack-sharp.

I hope this helps.

-PB.

ps: I could've sworn the name in the post header was 'Bran'. Maybe I just flaked out there for a minute.

Thanks guys! This makes much more sense now, and in retrospect is really quite intuitive. I wonder how many more "intuitive" techniques I am completely obivious too.

Don't worry Brian. I have been using either Elements or full CS2 for about 5 years now and feel like I have a pretty good handle on a lot of it. I am still finding intuitive techniques I have been oblivious to.

As I tend to joke, if you can't do the same thing three different ways in PS, you don't know how to do it in the first place

"As I tend to joke, if you can't do the same thing three different ways in PS, you don't know how to do it in the first place "

Truer words were never spoken, Dan!

-PB

Only 3 different ways???? Seems to me every time I turn around someone else comes up with 2 more to get the same outcomes. It makes my head hurt.

For little web sized images sharpening skies or smooth color tone areas has little effect if done modestly, however when processing a highly scanned film or maximum size digital image at the limits of capture, one is near noise and grain limits so just a bit of sharpening may make such visible in maximum sized output prints. Accordingly I almost never sharpen skies, shadows, or larger smooth areas like calm water for my large Lightjet print file outputs and rather select them out as alpha channel selections that are saved with the Photoshop .psd file. Such selections must be carefully tweaked at non-selection boundaries to prevent artifacts as halos. In some cases like tree subjects up in the sky with lots of small sky areas poking through branches, selection may be too much effort to be worthwhile resulting in a need to sharpen with localized brush tools. Likewise for image areas that are sharpened, artifacts increase as one prints to these large maximum sizes. I personally do not like seeing sharpening artifacts in prints though am often surprised how over sharpened displayed prints have been processed that readily shows up as grainyness in smooth rocks and noise in shadow areas. ...David

Yeah, don't sweat it Brian. Photoshop is nearly unfathomable, there's so many ways to do things. I've been using it since 2.5 and still regularly get hit by Ahaa! moments. All the concussions have made me woozy.....

I've been using a Photoshop Action I found online that first does an edge selection, lets you choose a threshold for the selection, then runs Unsharp Mask on that selection. This allows you to select detail in the image instead of the areas of smooth color, as described above. I've been really happy with it. Give it a shot.