Frozen marching ants on picture

[Diapositivo]

[attachment=3522:attachment]

Let's say you have a picture like the picture hereby attached: there is a clear separation between sky and ground, so I think: I will first select the sky, apply energic noise reduction to the sky, then apply milder noise reduction to the rest of the picture. That's not rocket science so far.

So I select with the "magic wand" the sky, make a separate layer of it "via cut", apply noise reduction, then go back to the (now skyless) background, apply milder noise reduction, than flatten the image.

The result was a broken line of white pixels along the borders between the two layers.

The second attached picture shows the effect, I hope the white ants are visible.

[attachment=3523:attachment]

My questions are:

a) Is this something to bother about? Or it is just so ridiculously tiny that nobody would ever notice? (I don't print my images myself, I propose them to agencies and hope for the best).

 If it is something to mind, how can I avoid it or, as a second option, is it there a quick fix to this?

Thanks
Fabrizio

PS Another question I asked was read by more than 180 people with no answer. I understand maybe the question is too obvious for navigated people. Still I would be very glad if I could receive "a clue".

[Richowens]

Fabrizio,

 Before you flatten the image deselect the sky, then flatten.

 Another way is to select the sky, don't "cut" but apply NR to the sky, then invert the selection and apply NR to the other part and deselect.

 Rich

[mahleu]

After you have selected, go to the select menu>modify>feather . This makes the edge of your selection fuzy so that any changes you make blur into the surrounding area.

[Jonathan Wienke]

I select with the "magic wand" the sky, make a separate layer of it "via cut", apply noise reduction, then go back to the (now skyless) background, apply milder noise reduction, than flatten the image.

The cut/paste is your problem. Select sky, feather selection a few pixels, NR, invert selection, NR again, remove selection. No seams will be left.

[Lisa Nikodym]

Try this:

After you select the sky, go into the "quick mask" mode, choose the brush tool with an appropriate size, make it very soft (i.e. zero hardness),  and run the brush over the sky/land edge.  (You can experiment with whether the white brush or the black brush gives you better results.)  This makes the edge of the selection more gradual.  A small region near the edge will have too much or too little noise reduction, but it's better than a sharp white line.

Ciao,
Lisa

P.S.  I wrote this just before mahleu & Jonathan posted.  That will do something very similar.

[jjj]

After you have selected, go to the select menu>modify>feather . This makes the edge of your selection fuzy so that any changes you make blur into the surrounding area.
[a href=\"index.php?act=findpost&pid=144909\"][{POST_SNAPBACK}][/a]

or Cntrl+Alt+D / Cmd+Alt+D is the easier shortcut.

[Wayne Fox]

Another option is after you have made your selection, duplicate the layer, then select the mask icon.  The mask will be created from your selection.  Clear the selection, then select the mask and run a slight gaussian blur to soften the edge of the mask - nice blend with no chance of any mising information.  Of course you can always edit the mask to clean up areas of the selection that the magic wand missed.

At this point you can run your two versions of NR, and on the sky can even be a little aggressive if you want, and then dial down the opacity of the layer to tweak the NR.

This works pretty good with sharpening as well ... over sharpen a duplicate layer slightly then fine tune by lowering the layers opacity.

[med007]

Another option is after you have made your selection, duplicate the layer, then select the mask icon.  The mask will be created from your selection.  Clear the selection, then select the mask and run a slight gaussian blur to soften the edge of the mask - nice blend with no chance of any mising information.  Of course you can always edit the mask to clean up areas of the selection that the magic wand missed.

At this point you can run your two versions of NR, and on the sky can even be a little aggressive if you want, and then dial down the opacity of the layer to tweak the NR.

This works pretty good with sharpening as well ... over sharpen a duplicate layer slightly then fine tune by lowering the layers opacity.
[a href=\"index.php?act=findpost&pid=144962\"][{POST_SNAPBACK}][/a]

Fabrizio,

You have now recieived a number of suggestion, but in common they all feather the junction between different regions. Still, applying any filter distances the image from how it was before. More often than not as we are concentrating our minds on one effect we can easily use too much of it! Almost always we need to step back or do something else and comeback.

I always try to add back some of the previous "original" state allowing one to maintain a sense of "genuine-ness" in the picture.

Asher

[Diapositivo]

Thank you very much, your advice solved the problem and tought me some basic tecniques.

I was applying "aggressive" noise reduction because I am working with scans, which always require NR and sharpening to obtain a natural-looking picture.

I was cutting and pasting to another layer because I use NeatImage as a NR software (it does not work within a PS selection, or at least, it does not seem to).

Actually I did not even know I can apply PS filters within a selection without doing any kind of masking or creating a layer!

Feathering edges solves the problem if I use NeatImage, and working within the selection solves the problem if I use PS NR.

Many thanks to all of you!

Fabrizio