removing sharpening halo

[gandini]

Let's say I have a sharpened photo and I want to remove the halos. I can't go back to the original. Does anyone know of an action (PS) to remove the halos? Since the sharpening action produces the halos, why not something like a *reverse-sharpen?" Of course this would take the form of a selective blur, or something.

cheers and thanks

[bruin70]

well, i'm not familiar with PS, and i'm not a photographer. i'm an artist. but here's what i'd do with paint shop pro if i can't "undo".

first off, if there's a way to incrementally blur, i would try to get rid of the "noise" at blur's lowest setting.

if you only want to work on certain areas, magnify to very very close and airbrush by hand to soften the edges. you'll be surprised at what you can get away with. i personally would airbrush, because you can create a transitional color/value passage over the halo.....if you use a blur tool, you might not get rid of the halo itself(only blur it. the halo is as much a value change as it is an edge change) and you will create another type of halo, a "blur" halo.

if you airbrush, lower both the density and opacity to between 10-20. and you don't have to TOTALLY change the halo,,,just tone it down.

[dtrayers]

Have you tried the High Pass method of sharpening? You don't get as much 'halo-ing'.

http://www.luminous-landscape.com/tutorials/high-pass-sharpening.shtml

I use this technique, and I've experimented with using a smart blurr on the high pass layer to blurr out the "noise" that you may get. You can also try the "soft light" blend for a lesser effect.

[Conk]

Philip
This is a very good question. I have an idea or two but I'm going to research this one out and post my findings.

[slejhamer]

Your message indicates you are trying to fix an image that was already sharpened but shows excessive haloing, rather than avoiding the problem in the first place. Correct?

I haven't tried this yet or or thought of the individual steps, but intuitively it seems you could:

1. Create an edge mask. For simplicity, you can pilfer the first part of Fred Miranda's free 8-bit sharpener. (There are many ways to create an edge mask, but this is pretty good.)

2. With the edge mask selected, select color range > highlights. That should capture just the halo highlights around the edges. (I assume that leaving shadow areas is okay, and that the highlights are the problem.)

3. I'd probably try feathering, blurring, or tweaking the selection, but I'm not sure where to go with this. Maybe this step should come before the color range selection, with the "minimum" or "poster edges" filters run on the edge mask. For now call it optional.

4. With the highlights selected, you can edit > fill them in with 50% gray (or a lighter tone), or run curves and tone them down that way, or whatever. Or put them on a layer set to multiply. Lots of options.

More options: somewhere along the way you'd want to consider an anti-aliasing technique to remove color distortions along the edges. Better a white halo then a magenta one, I'd think. Maybe step 4 could be a color blur of the feathered highlights, set to darken? As with all things in photoshop, there are numerous ways to skin this cat.

Hope that is useful.

[gandini]

Thanks Mitch, you are right about not having the option of avoiding the haloing in the first place. The problem arises because I have downloaded some wall paper from a MotoGP website (it's free for personal use.) I need to resize the image to fit my large wide screen notebook. Using Fred's latest SIpro I get great enlargments but it highlights the haloing from the rather poor sharpening algorithm used in the original image. Hence my idea of blurring the halo, or some of your other suggestions, then re-sharpening with Fred's ISpro, which works very well as a large image sharpener and I suspect will give a far better result.

I'll start with the edge mask from ES8.
And thanks to Conk for any other ideas you have.

cheers,