Hey folks,

I was once again thinking over the techniques to enhance some photoshop things and one thing that always disappointed me was the sharpening.

Let's have a look on how sharpening works:

Sharpening is basically tricking the eye. A blurred gradient to another color is sharpened by filling the adjacent areas with the inverted color. Disadvantage: Halos. But why must there be Halos?

Photoshop calculates the inverted color by simply using the invert color (what a statement :). It does not use the color on the other side of the gradient which would produce no halos at all. An example:

We have a gradient from yellow to green. Sharpening this gradient means Photoshop adds magenta next to the green area and blue next to the yellow area hence it reduces in heavy halos. If it used the adjacent area as a fill color, there wouldn't be any shadows, but how can that be done?

An interesting question isn't it?

Wonder if any of you know a solution :)

Patrick

I've been pretty happy using FocalBlade (http://thepluginsite.com/products/photowiz/focalblade/) to sharpen. It doesn't seem to introduce the color aberrations in the area of the edge, and it deals with halos very well.

We have a gradient from yellow to green. Sharpening this gradient means Photoshop adds magenta next to the green area and blue next to the yellow area hence it reduces in heavy halos. If it used the adjacent area as a fill color, there wouldn't be any shadows, but how can that be done?

yes, but then it wouldnt be 'sharpening', it would be blending or smoothing by gradient. sharpening can be done two different ways that i know of. i'm not sure which photoshop or the other programs use, but you can sharpen by contrast, or you can sharpen by brightness. i think Paint Shop Pro uses by brightness.

if you look at a color wheel, the method you are describing in the part i quoted, is based on complementary colors. i would assume this is done for the sake of contrast. the complementary color of green is magenta and the complementary color of blue is yellow. thus, you get a nice contrast.

Craig

Craig, that is exactly what I am talking about!

Photoshop uses the complementary color to add contrast, hence sharpen. If it used the adjacent color instead, there wouldn't be any halos, right? So the question:

How do you achieve a sharpening with the adjacent color instead of the complementary one?

patrick,

when you say 'adjacent' do you mean adjacent in the color wheel or adjacent in the image? i'm guessing you mean adjacent in the color wheel. so, if you had a green, you'd either turn it cyan or yellow. well, green next to cyan or yellow isnt going to sharpen so much as it is going to blend. obviously it's not a complete blend, but that's just talking about the pure colors.

quite honestly, i dont know what you could use to do what you want. like i said before, sharpening is generally done with either contrast in color or contrast in brightness. but, it would make sense to have degrees of this or even combinations of this, or to have a tool where you could set the sharpening parameters. i just dont know of such a filter/plugin or tool that would allow this.

sounds like a great tool though. maybe we can commission one to be written.

Craig

I would suggest you get onto thelightsright.com. You can download what is arguably the best professional sharpening tool kit available. It's free and comes with a superb how to tutorial. Definetly worth your while to check it out. I use it with outstanding results.

Dave

Dave,

I'll give this one a look, thanks!

Craig,

I did not mean adjacent in the color wheel but in the area to be sharpened! Let me give you an example about what I meant: Suppose you have a portrait with black background and the image is a little blurry so you decide to sharpen it. Photoshop would sharpen this by adding complementary color to the other side of the gradient (what basically every edge is) and this is what produces halos:

The complementary color of the black background is white, so it will add white to the skin. The complementary color of skin is something blue-cyan and this is what produces a blue-cyan halo in the black background. Halos.

But what if Photoshop would not use the complementary color to add it to the other side of the gradient, but increase the saturation instead on both sides. An edge is as we said just a gradient, so one color fades into another one. If you increase the saturation or opacity of both colors, this would narrow the gradient until you have an extremely sharp picture. Thus the gradient should be shrinked to a thin line, right?

Patrick

ah, ok. that's another matter then. that gradient is there for a reason. and the reason has somewhat to do with dithering/anti-aliasing. maybe not completely, but somewhat. if you raise the saturation on both sides, you're lessening the grays, whites, and blacks in the hue. that's what saturation is, a lessening of the grays, whites and blacks. you probably would get an increase in the definition of the edge, but not necessarily in all cases. you would also get a lessening in the anti-aliasing/dithering, i would think. not sure if all that would be good, bad or what. i would guess that adobe did what they did based on some sort of average result testing. not sure the saturation increase would give you as good an average over many cases.

but that's about as far as i can think with it at this point. it would be somewhat interesting to do a test on this. and i certainly wouldnt mind if there were more options in setting the parameters for things like sharpening.

Craig

Patrick

This post has lost me a little but not altogether.

Isn’t this the reason a lot of people change to LAB to do the sharpening

There is also an argument for sharpening the image a little and then repeating it many times

One last thing that I found
If you sharpen on a layer and then set the mode to "Darken"
Then only the pixels that have been darkened by Unsharp Mask Will be Added.
This is one way of eliminating the artificial "halo" that sharpening produces since the "lighter than" pixels weren't used.

Ken

True, both posters :)

What I thought of was somethink like: You have color a on one side and color b on the other. Why not find the "edge point" where both of them come together (something similar to find edges but only producing a one pixel wide) and draw a line with two colors there and set the color on both sides to the same as the area "near the edge is".

I illustrated it a little in the attached image. Sharpening in LAB would also lighten the areas and hence shift colors :(

ok, new day and my head isnt quite so full of mush, so let's look at this again.

ok, i've no idea what program or plugin might do this. sounds feasible, though. have you tried this in some way on real images at all? i mean, manually. and, whereas i dont have a decent version of photoshop, would any of their actions or scripts or filter factory allow you to make something like this? or maybe filter meister, if you can code a bit?

it sounds like an interesting project to me and i'd be happy to test the beta plugin :)

Craig

Hey all,

I just laid back, watchin a game, havin a bud when I remembered writing an email to Adobe about the sharpening idea. I thought about what to write and suddenly it popped into my mind!

I tried this technique with a simple gradient and the result was awesome, haven't tried on a real picture yet, but if someone wants to have a go before I do.... So that's the technique:

- Create a copy of the background layer
- Go to Image/Adjustment/Brightness & Contrast (just for convenience) and increase the contrast by a few numbers until the edges look real sharp, don't care about anything else. Adding contrast will almost always accentuate the edges but heavily ruin the image by now :)
- Go back to the background layer and select luminosity by pressing ctrl-alt-~
- Go back to the new layer and add a mask with that selection
- Image/Adjustments/Curves and drag the white anchor to the bottom, create a new anchor in the middle and drag it right up to the top to reveal only midtones
- Set layer mode to Soft Light
- Magic!

This is basically a mix of the Hi-Pass Sharpening and the idea of contrast adding more sharpness. I gave it a quick try on a photo but the results were less than worse, but maybe with a little tweaking here and there...

Applause or laughter from anyone? :)

Patrick

Also try a reverse luminosity sharpen....... In rgb, instead of just sharpening the composite channel as a whole on a luminosity layer. Do a Ctrl/Command + Alt/Opt + "~"... then do a Shift + Ctrl/Command + "I" ......Hide the selection edges, if that bothers you. Then use the unsharp mask. When you use the unsharp mask, use conventional sharpening or the "HaLo" (High Radius, Low Amount) method. This reverse luminosity sharpen, sharpens "detail". Something, like a black channel sharpen in cmyk.



John

I'll put this out again. If you're looking for sophisticated sharpening capabilities..and more, check out TheLightsRight.com Sharpening Tool Kit and Tutorial.

Cheers

Dave

patrick,

besides what duv said, and since posting here last, i found a filter plugin you might be interested in. it's called '7 band sharpening filter'. i've tried it a few times. dont know if it's doing what you suggested, but it does give a bit more control over how you sharpen images.

Craig