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robirdman1
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making white sky blue without artifact in leaves, bird feathers

Jun 8, 2012 5:52 AM

Is there some good way to do this when there are subjects that have many small features, sure as leaves or bird feathers? I have tried different selection methods and feathering, but always wind up with halos or sudden changes at the boundary, that necessite huge amount of detail work to get rid of, 

 
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  • Currently Being Moderated
    Jun 8, 2012 6:42 AM   in reply to robirdman1

    Hahaha … if there is next to no contract between sky and (light) birdfeathers how do you imagine this process should operate?

     

    In any case posting en example (maybe only some sections) might give us a better idea what you are dealing with exactly.

     
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    Jun 10, 2012 5:53 AM   in reply to robirdman1

    I’m afraid the Magic Wand is a bad fit for this task.

     

    A combination of a Lab-channels-based selections, some painting and Blend if-settings might be useful.

    slyColorTiff.jpg

     
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  • Currently Being Moderated
    Jun 10, 2012 8:57 AM   in reply to robirdman1

    robirdman1,

     

    here comes a tutorial:

    http://www.fho-emden.de/~hoffmann/skyblue14072008.pdf

     

    Please, try to become familiar with Photoshop Lab - that would

    be very helpful.

     

    Best regards --Gernot Hoffmann

     
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  • Noel Carboni
    23,469 posts
    Dec 23, 2006
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    Jun 12, 2012 4:41 PM   in reply to robirdman1

    Honestly, an aggressive replacement of that sky comes off looking pretty unnatural.

     

    Have you tried Image - Adjust - Color Balance and just nudging Highlights toward Blue?  If doing so seems to shift everything too much to blue, you can counteract some of it by shifting Shadows in the other direction...

     

    HighlightsToBlue.jpg

     

    -Noel

     
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  • Currently Being Moderated
    Jun 12, 2012 11:15 PM   in reply to robirdman1

    robirdman1,

     

    yes, I should have written 'apply Select > Inverse'  twice, in order to make

    the selection boundary at the image boundary visible by 'running ants'.

     

    The purpose of the doc:

    1)  How to avoid accurate selections by using Magic Wand or Polygonal

    Lasso. The technique of conditional blending (blend if) requires some

    exercise.  My doc contains the explanations for C.Pfaffenbichlers recom-

    mendations #3.

    2)  Answering the question 'which color is sky blue?'

    3) How to apply Photoshop Lab

     

    Noel #7 is right - there are many methods how to achieve an effect.

     

    Best regards --Gernot Hoffmann

     
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  • Currently Being Moderated
    Jun 12, 2012 11:22 PM   in reply to Gernot Hoffmann

    Gernot, your link won't save as a pdf so I had to bookmark it.

     
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  • Currently Being Moderated
    Jun 13, 2012 12:59 AM   in reply to robirdman1

    I dont think using features such as lab are really all that nessary in this case. I would go for a hue-satuation adjustment or color balance(highlights) and then invert the default mask. Then simpy paint on the areas that you wish to be blue. I would make this very subtle however, becasue you could end up with something very unnatural if you go too crazy...

     
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  • Currently Being Moderated
    Jun 13, 2012 10:26 AM   in reply to Lundberg02

    Lundberg02 wrote:

     

    Gernot, your link won't save as a pdf so I had to bookmark it.

     

    The link is working just fine, Lundberg02.  Just SINGLE-click on it (not double-click, not right-click, and not Control click) on the Mac and the PDF downloads right away.  As a matter of fact, check your downloads history, you may have already downloaded it more than once. 

     
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  • Currently Being Moderated
    Jun 13, 2012 11:09 AM   in reply to station_two

    Thanks, station_two,

    I had tested the PDF again - it's really OK. Nothing 'download protected'. 

     

    A related doc about image processing in the color space Photoshop Lab:

    http://www.fho-emden.de/~hoffmann/labproof15092008.pdf

     

    Best regards --Gernot Hoffmann

     
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  • Currently Being Moderated
    Jun 13, 2012 3:43 PM   in reply to Gernot Hoffmann

    Station_two is right, there's nothing wrong with the link, but as I posted in a new thread, it seems that I can't save a pdf from Safari 5 in 10.7.4. Gaack!  I d/l both your links from Firefox instead. I tried some other pdfs, same deal. Now WTF.

     
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  • Currently Being Moderated
    Jun 16, 2012 6:23 AM   in reply to robirdman1

    robirdman1,

     

    I don't have the time to give answers to all your questions. But

    let me explain just one problem: How can we convert white sky

    into blue sky?

     

    Basically it's done by the mentioned method, in Lab and using

    conditional blending (blend if), as explained in my docs (based

    on Dan Margulis' book about Lab).

     

    Below we can see the original image and the improved image

    which shows as well a very coarse selection for the sky.

    The sky in the background is white. Converting white into blue

    requires two steps:

    1) Reduce the Lab-Lightness drastically. Bright white cannot be

    made blue.

    2) Shift the b-curve towards blue.

     

    I'm aware of the difficulties using Lab. But it's worth the effort.

     

    Images are not sharpened again after downsampling. Based

    on screenshots in order to show the selection.

     

    Best regards --Gernot Hoffmann

     

     

    Ercole-0325-02-small.jpg

     

    Ercole-0325-05-small.jpg

    Corso Ercole I d'Este, Ferrara, Italy

     
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  • Noel Carboni
    23,469 posts
    Dec 23, 2006
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    Jun 16, 2012 10:04 AM   in reply to robirdman1

    Color Balance isn't the only tool you have...  For the reddish sky in the image you showed above of the Black Capped Night Herons, I'd suggest Image - Adjust - Curves, then pull the white point of the Red curve down a little.  Adjust the Green curve similarly, though less - to taste.  If you want to get fancy, keep the luminance the same after that adjustment by doing Edit - Fade Curves - Color.

     

    BluerSky.jpg

     

    How did I know to do that?  Look at the light parts of the image - they're reddish.  First thing that came to my mind was to reduce the reddish light.

     

    -Noel

     
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  • Noel Carboni
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    Oct 15, 2012 10:19 AM   in reply to robirdman1
     
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  • Noel Carboni
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    Dec 23, 2006
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    May 17, 2013 2:15 PM   in reply to robirdman1

    Sorry for rehashing the basics, but...

     

    • Do you have the image layer targeted?
    • Image portion of the layer (vs. mask) targeted?

     

    Perhaps if you'd take a screenshot of your entire Photoshop environment at the moment of the error and post it here someone will be able to spot something that's not set right.

     

    Photoshop is quite modal, and if you don't have everything just so, it can be unforgiving.

     

    -Noel

     
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  • Currently Being Moderated
    May 18, 2013 1:35 PM   in reply to robirdman1

    Your dialog has "Show Amount of: Pigment/Ink" enabled. Switch it to "Light" to get expected result when you pull down the curve.

     

    Screen shot 2013-05-18 at 21.31.37.png

     
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  • Noel Carboni
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    Dec 23, 2006
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    May 18, 2013 2:54 PM   in reply to conroy

    Conroy's got it right.  I've noticed over time that the grayscale curves dialog sometimes reverts to "backwards" operation.

     

    Once you swap it, then complete a Curves operation it should stick the "right" way again for future operations.

     

    -Noel

     
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  • Noel Carboni
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    May 18, 2013 6:00 PM   in reply to robirdman1

    You're welcome, for my part.  Thanks for making it easy to help.

     

    I've found that screenshots are a great way (with Photoshop at least) to get to an accurate answer.

     

    -Noel

     
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