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Author Topic: Halo problem when darkening blue skies  (Read 14574 times)
Redcrown
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« on: August 07, 2013, 12:10:38 PM »
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I often try to darken the blue in landscape skies. I've tried several techniques to darken the blue, but all leave halos around tree leaves, branches, and other hard edges. I know the halos are the result of natural light diffraction around edges. I've tried various techniques to remove the halos after the fact, but can't find anything that works well, other than tedious pixel level cloning. Wondering if anybody has a good method.

Here is a recent example, full frames on top, 200% crops on the bottom to show halos. The images on the left are before darkening the blues. The ones on the right are the result of using the HSL tab in ACR and dragging the blue luminosity slider all the way to the left.

Sometimes I try a B&W adjustment layer in luminosity mode and drag its blue/cyan sliders. Sometimes I try a Selective Color adjustment layer. All give similar results and halos.



Anybody wants to play, here is the raw/dng file.

https://dl.dropboxusercontent.com/u/62166185/ANwedding040v0.dng
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Peterretep
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« Reply #1 on: August 07, 2013, 02:49:08 PM »
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Diffraction?

Try the clone tool set to darken and sample near where correction is to be made.

Peter
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BartvanderWolf
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« Reply #2 on: August 07, 2013, 04:54:59 PM »
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I often try to darken the blue in landscape skies. I've tried several techniques to darken the blue, but all leave halos around tree leaves, branches, and other hard edges. I know the halos are the result of natural light diffraction around edges.

Hi,

What can have a natural cause, is specular reflection of the sun from the leaf surface, depending on orientation to the sun. A polarization filter can prevent some of that.

Quote
I've tried various techniques to remove the halos after the fact, but can't find anything that works well, other than tedious pixel level cloning. Wondering if anybody has a good method.

Well, it's a typical case of prevention being better than a cure. I gave it a quick try (a bit short on time right now), and I'm not too happy with the result, but it is so much better than your result that I still wanted to let you know that there is still hope for images like this. See the attachments for an example of what I get without knowing the optimum Raw conversion settings for your camera and lens.

I used Photoshop ACR (because you also did), although I would normally tackle such files with Capture One or RawTherapee. That may explain some of the things/artifacts I'm not happy about.

I used FocusMagic for Capture sharpening, and Topaz Clarity for halo free darkening of the sky and to add a fair bit of punch to the overall image.

Hope that helps for now.

Cheers,
Bart
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Paul2660
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« Reply #3 on: August 07, 2013, 05:09:51 PM »
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I tried to pull the file down, but only get a bit dump, not sure what I am doing wrong as Bart got it.  I tried the link on both win and mac.

As far the file, for sure a CL-PL will help on the main issue you are having.  You have to be care on this type of shot depending on how wide you are and where the camera lens is in relation to the sun, for you can get a light to dark fade.

I would try pulling down your highlights, slider, in LR 4.x or higher, not sure what version of ACR you are on, but the version of ACR that picked up the LR 4.x highlights slider is CS6 as I recall.  There is a huge difference between CS5 and CS6 in both highlights and shadows sliders.

Pulling down luminance is one way to work the sky to get more blue, however you have to watch that you don't go past the point of no return, which is where you are with the haloing.  I have often felt this mainly because there is a shade of blue, up close to the leaves that is not being effected by the luminance slider. 

Try pulling down the blue luminance in conjunction with the highlights slider if you are CS6 and then consider a ND gradient to the sky.  This will also darken the blue and should not effect the haloing as you are getting. 

Topaz Clarity is a great tool as already mentioned to help some, and the Clarity slider in LR 4.x or LR 5 will also help.  Also you can help this by pulling back a bit on the "whites" slider as it will tone down the area you are having troubles with.

Capture One's color picker works a bit better here in that you can select a blue right up by the leaves and try to darken it. 

If you can get me the file I would love to work it up.

Paul Caldwell
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Paul Caldwell
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kirkt
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« Reply #4 on: August 07, 2013, 10:19:56 PM »
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If you are trying to accomplish this in LR/ACR with HSL, try using the "aqua" slider instead of blue - slide the luminosity aqua slider to -100.  The effect is more natural, tonally, and there are no artifacts.  Skies are not "blue" sort of cyanish - why HSL has sliders like "aqua" and not "cyan" is puzzling.

Anyway, give it a shot.  The sky darkens, but does not look overly compressed.  The attached 100% crops are with ACR sharpening set to Amount 50, radius 1.0, detail 65, masking 55 (tending toward light deconvolution-like sharpening) to see if aggressive capture sharpening would accentuate artifact from this HSL move.  The small, complete image is from PS, reduced to 1600 px on the long edge, using bicubic - not output sharpening - try with the file and get it into the format you will use and then apply you sharpening to see if the edges at the sky-leaf borders can withstand this technique.

EDIT - you can also use the blue luminance slider to further darken, up to about -25, still with no halo edges; however, at that point the sky is unnatural in tone.

You can also set the combination of tonal controls in raw conversion to get the sky looking the way you want and then apply local modifications to the other elements for which it may be easier to build masks.

kirk
« Last Edit: August 07, 2013, 10:36:01 PM by kirkt » Logged
Tim Lookingbill
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« Reply #5 on: August 07, 2013, 11:47:21 PM »
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I don't have the current version of ACR that comes with PV2012 so I did the HSL/Curve edits in LR4 which uses the same sliders and PV2012 conversion engine.

Here's some screenshots with the settings I used and as a matter of fact skies are not cyan nor are they aqua, they have a magenta element to their hue just not as pronounced. Your sky has too much green in it and the HSL settings I used with the magenta hue shift aided in making the sky look darker along with the curve.
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Redcrown
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« Reply #6 on: August 08, 2013, 08:30:43 AM »
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Thanks all for the tips. For Paul, the Dropbox link bothers some browsers (Firefox) when you direct click on it. Just right-click and save as.

This sample is just my most recent. Usually I encounter this problem when doing B&W conversions and try to get dramatic black skies against white clouds.

Those dramatic black sky B&W landscapes were one of the primary reasons I got into photography 40 years ago. I saw it, liked it, and wanted it, thus built a home darkroom. It was achieved by using polarizers and heavy red filters on B&W film, and I don't recall ever having a halo problem.

It's interesting that doing a complete sky replacement, while hard work with some advanced masking, is often easier than fixing halos in the existing sky.
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Paul2660
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« Reply #7 on: August 08, 2013, 10:01:30 AM »
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Thanks, I forget that every once and a while.

I do better with Capture One Pro vr 7 on shots like this.  As this was a dng, Capture One wasn't able to get the Lens info for some reason, so I had to reimport to LR to work a bit of CA.  

I have attached a crop of my final workup.  I was concerned about blowing out the flowers on the wagon, but still holding the sky.  Capture One IMO has a bit better selective color tool set, but that is just my opinion.  

Thanks for the opportunity.   Be more than happy to send the whole image, just drop me an email.

NOTE, the attached thumbnail does not have the right tone of blue, however when you double click and view it the color is fine. 

Paul Caldwell
« Last Edit: August 08, 2013, 10:03:13 AM by Paul2660 » Logged

Paul Caldwell
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David Eichler
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« Reply #8 on: August 09, 2013, 11:22:25 AM »
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Thanks, I forget that every once and a while.

I do better with Capture One Pro vr 7 on shots like this.  As this was a dng, Capture One wasn't able to get the Lens info for some reason, so I had to reimport to LR to work a bit of CA.  

I have attached a crop of my final workup.  I was concerned about blowing out the flowers on the wagon, but still holding the sky.  Capture One IMO has a bit better selective color tool set, but that is just my opinion.  

Thanks for the opportunity.   Be more than happy to send the whole image, just drop me an email.

NOTE, the attached thumbnail does not have the right tone of blue, however when you double click and view it the color is fine. 

Paul Caldwell

Well, that seems to be a significant advantage of C1 over LR/ACR. Does DxO work as well in this regard?
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Kirk Gittings
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« Reply #9 on: August 10, 2013, 12:00:51 PM »
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Good thread with lots of good info. Time to spend some time experimenting. This has been a problem for me since I went digital.
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Thanks,
Kirk

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Tony Jay
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« Reply #10 on: August 10, 2013, 06:01:17 PM »
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Schewe covers this issue in The Digital Negative.
Blue + yellow = white. He then suggests a technique to solve this in post.

Tony Jay
« Last Edit: August 10, 2013, 06:03:00 PM by Tony Jay » Logged
BartvanderWolf
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« Reply #11 on: August 10, 2013, 07:09:49 PM »
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Schewe covers this issue in The Digital Negative.
Blue + yellow = white. He then suggests a technique to solve this in post.

Hi Tony,

Maybe, but I prefer prevention before cure. With proper (capture) sharpening, based on a good Raw conversion, it is possible to prevent most of the issues.

Cheers,
Bart
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David Eichler
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« Reply #12 on: August 10, 2013, 10:53:41 PM »
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Hi Tony,

Maybe, but I prefer prevention before cure. With proper (capture) sharpening, based on a good Raw conversion, it is possible to prevent most of the issues.

Cheers,
Bart

Talking acr/lr? In my experience, no matter how moderate the clarity and sharpening, such haloes will start to appear with a substantial selective darkening via luminosity with the HSL controls.
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Kirk Gittings
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« Reply #13 on: August 10, 2013, 10:58:32 PM »
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Talking acr/lr? In my experience, no matter how moderate the clarity and sharpening, such haloes will start to appear with a substantial selective darkening via luminosity with the HSL controls.

Mine too.
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Thanks,
Kirk

Kirk Gittings
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ErikKaffehr
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« Reply #14 on: August 11, 2013, 01:29:03 AM »
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Hi,

I sometimes use Photoshop create a new layer, multiply and use a luminosity mask. The technique is described here:
http://echophoto.dnsalias.net/ekr/index.php/photoarticles/46-fixing-sky-with-luminosity-mask

The haloing you see is probably mostly an effect sharpening.

Best regards
Erik
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BartvanderWolf
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« Reply #15 on: August 11, 2013, 06:18:55 AM »
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Talking acr/lr? In my experience, no matter how moderate the clarity and sharpening, such haloes will start to appear with a substantial selective darkening via luminosity with the HSL controls.

Hi David,

Besides the already mentioned specular sky/sun reflections of the edges of leaves, good processing will minimize artifacts.

It starts with proper Raw conversion and Capture sharpening (I prefer better tools like FocusMagic instead of ACR/LR). It does seem like e.g. Capture One  Pro (V7 is significantly improved) or the free RawTherapee (AMAZE demosaicing algorithm) can sometimes extract a bit more resolution out of a given Raw file, which may help. Then it continues with non-halo inducing contrast adjustments, Topaz Clarity is a good example of how it could/should be implemented.

Finally, darkening the blue of a sky by HSL adjustment should not create halos that are not already there. It may enhance the visibility of halos and of the specular reflections on some of the leaf edges, but then those reflections are not halos but rather image detail. Since the darkening by regular HSL usually also creates a color shift (blue -> magenta), I prefer the HSL controls that Topaz Clarity offers, they leave the color intact. Very clever folks at Topaz Labs!

So the whole thing boils down to carefully selecting and then mastering the tools one uses.

Cheers,
Bart
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David Eichler
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« Reply #16 on: August 11, 2013, 02:23:25 PM »
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Hi David,

Besides the already mentioned specular sky/sun reflections of the edges of leaves, good processing will minimize artifacts.

It starts with proper Raw conversion and Capture sharpening (I prefer better tools like FocusMagic instead of ACR/LR). It does seem like e.g. Capture One  Pro (V7 is significantly improved) or the free RawTherapee (AMAZE demosaicing algorithm) can sometimes extract a bit more resolution out of a given Raw file, which may help. Then it continues with non-halo inducing contrast adjustments, Topaz Clarity is a good example of how it could/should be implemented.

Finally, darkening the blue of a sky by HSL adjustment should not create halos that are not already there. It may enhance the visibility of halos and of the specular reflections on some of the leaf edges, but then those reflections are not halos but rather image detail. Since the darkening by regular HSL usually also creates a color shift (blue -> magenta), I prefer the HSL controls that Topaz Clarity offers, they leave the color intact. Very clever folks at Topaz Labs!

So the whole thing boils down to carefully selecting and then mastering the tools one uses.

Cheers,
Bart

With the example above, the "halo" effect is clearly not in the original file. With ACR/LR, haloing starts to appear with substantial darkening of the sky, even with little or no clarity or sharpening applied. The example processed with Capture One shows no haloing with substantial darkening of the sky. Seems fairly conclusive to me, although we don't know what clarity and sharpening settings were used for the Capture One example, and whether any compromises had to be made in this regard.

So, I don't really understand your comment about "proper" RAW processing, unless you are saying that you don't feel that ACR/LR permit such RAW processing, relative to other current options. BTW, I still see some haloing in your example with Focus Magic. I see none at all in the Capture One example.


« Last Edit: August 11, 2013, 02:31:37 PM by David Eichler » Logged

Ray
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« Reply #17 on: August 11, 2013, 08:28:35 PM »
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Hi Bart & Erik,
This problem of halos, when darkening a sky only, is a problem that I also experience. Sometimes, before making a large print where such halos would be noticeable on close inspection, I have in the past enlarged the image about 400% on screen, carefully made selections around the haloed areas, and used the Healing brush to fill in such areas with the adjacent sky.

This process is tedious enough when the halo is along a fairly uncomplicated edge such as the top of a mountain range, but far too tedious when the haloed edges take the form of leaves and branches.

It would be greatly appreciated if Bart or Erik were to use Redcrown's DNg file as an illustration to show us step by step, in ACR and Photoshop because that's what I use for all my processing, how that sky could be darkened to the same degree that Redcrown has done, without the obvious halos.

Erik's example in reply #15 does not show a significantly darkened sky.

Cheers!
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BartvanderWolf
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« Reply #18 on: August 12, 2013, 07:13:15 AM »
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It would be greatly appreciated if Bart or Erik were to use Redcrown's DNg file as an illustration to show us step by step, in ACR and Photoshop because that's what I use for all my processing, how that sky could be darkened to the same degree that Redcrown has done, without the obvious halos.

Hi Ray,

See the attached examples.

The first attached image is a crop of a straight ACR conversion, no sharpening or Clarity at all. As can be seen, there are no real halos present, but there are a few specular reflection edges where the bright background illumination, bounces of the leaf and branch edges. That nature for you.

The second image took that crop and had it's (HSL Blue) Luminosity reduced to 50% by Topaz Clarity (no other contrast adjustments were activated, only HSL). The Lab chromaticity remained almost the same, which is not possible in Photoshop, hence my recommendation to use a better tool, like Topaz Clarity. I also used an automatic color range mask to select the blue of the sky and leave the blues in the rest of the image alone. The extreme darkening created a few problem areas, but with the great masking tools of Topaz Clarity it was not hard to touch-up a few spots on branches. These problems usually do not occur, but the extreme darkening of a single color range triggered them.

The third image is the second image with some FocusMagic deconvolution sharpening applied. Nothing excessive, because this area was not in the focus-plane to begin with, but rather in the back of the DOF zone (and f/11 reduced a lot of micro-contrast anyway). The specular reflection edges gained some contrast, but at normal viewing magnification that doesn't hurt the image at all. No large halos appeared, because there were none to begin with really.

And finally a screen capture of the three next to each other, zoomed in.

Hope that helps.

Cheers,
Bart
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Ray
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« Reply #19 on: August 12, 2013, 08:56:49 AM »
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Thanks, Bart.

The first crop of the straight ACR conversion looks the best to me. No halos at all.
It seems you've used Topaz Clarity and Focus Magic to darken the sky, sharpen the leaves which don't seem to benefit from sharpening, and produce halos which are not as obvious as in Redcrown's version, but still noticeable.

What I'd like to see is the first version with no halos at all, but with a darker sky as in the second and third versions. I guess this isn't possible. Right?
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