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  • Blue-atmospheric haze

    How can I correct the blue-atmospheric haze seen in many of the photos I took of the Grand Canyon on a recent trip there?
    Thanks for any help you can give me. Tom
    Attached Files

  • #2
    Tom, the problem is the human eye auto adapts and neutralises the white/black/grey points in the image - while the camera faithfully records the scene, blue haze and all.

    The solution, simply setting endponts and neutral tones - in this case the highlights and neutrals were pretty good...it's the shadows that are the problem, with the blue channel being the major issue.

    This correction was done with the simple levels/curves eyedropper tools in Photoshop.

    I chose a dark area of the cliff in the foreground as the shadow point.

    Some sharpening was also applied.

    More can always be done, this is pretty quick if you have a lot of images to process, but not an automated (fully) process.

    Some very good links on colour correction and the theory behind the moves (image evaluation etc) can be found here:

    http://members.ozemail.com.au/~binar...V_links.html#C

    See attachment below for the correction example.


    Hope this helps,

    Stephen Marsh.
    Attached Files

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    • #3
      I used a curves adjustment layer set to luminosity mode and adjusted the individual color channels seperately Then I bumped the red value up slightly with a hue/saturation adjustment layer.



      Ken
      Attached Files

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      • #4
        Ken,

        I am confused. I don't know how to set luminosity mode for curves. Did you mean you used color balance with preserve luminosity selected?

        Thanks,
        Catia

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        • #5
          Originally posted by catia
          Ken,

          I am confused. I don't know how to set luminosity mode for curves. Did you mean you used color balance with preserve luminosity selected?

          Thanks,
          Catia

          The way I do it is use a curves adjustment layer, ok the curves adjustment without making any adjustments and on the curves layer set the mode to luminosity, then double click on the curves layer to go back inand make your adjustments. Doing this, the colors won't shift. Hope I explained this well enough.


          Ken

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          • #6
            Wow, what a challenge!

            I came to the same conclusion as Stephen that the shadows suffered the most here. I tried several fixes with histograms and levels, with some good success. However, I tried one experiment that really popped in my eyes:

            Layers (from the bottom):
            1) Original Image
            2) Copy of original's Blue Channel, colorized to Blue/Cyan (Hue=210 from 360), Opacity~30%, Blend=Difference
            3) Adjustment: Levels to taste

            This was a happy accident. I indended to subtract out pure blue, but miscalculated the hue. When I went back and did it pure blue, the results were poor. Getting rid of the green seems to help.

            Thanks,
            Jeff
            Attached Files

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            • #7
              The human eye sees the shadows as a deep _neutral_ so that is what we should probably correct for. The camera sees the shadows as blue. We need equal values in the R, G and B channels somewhere in the shadow section. This can be done by hand or the eyedroppers - it does not really matter.

              If an image should have white/neutral/black points and it does not - chances are it can look a lot better by forcing these key target zones to be true...the rest of the image often snaps into place (to some degree).

              But without removing blue (adding yellow) from the entire tonal range of the image - it will still suffer, as this is the major problem (lack of range/contrast and impossible colours for key memory points on the image).


              Stephen Marsh.

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              • #8
                Thanks for the help, guys. Your results are great but I'm interested in the fact that there are differences in the color casts in the different images. The Grand Canyon and the whole area from Monument valley to Bryce Canyon is composed of that reddish rock. It sometimes seems imposible that the rock could be that color, especially at sunrise or sunset. Tom

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                • #9
                  I have tried this on mt. pics and it works well.
                  Unsharp mask
                  amt. 30 radius 60 threshold 1

                  Learned this at dpreview forums. I think Isabel posted it.

                  Other settings to try USM Amt. 50 Radius 100 threshold 2

                  Just have to play with the settings for different pics.
                  This is at USM 30 60 1

                  hope that helps
                  Attached Files

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                  • #10
                    and this one with the USM at 50 100 2
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                    • #11
                      Here is my take. Unfortunately the colors never look the same on web because my Photoshop is configured for newsprint output, and as soon as I view the file in another program it looks awful.

                      edit: done w/ 3 adjustment layers
                      1 for the whole pic minus some of the foreground bushes. This one was just to set the black and white points of the image.
                      1 for everything minus the sky. To punch up color and brightness (which suffered after setting the black point).
                      1 for the sky only, to make it "match" the rest of the pic.
                      Attached Files

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                      • #12
                        http://members.ozemail.com.au/~binar...V_links.html#C

                        http://www.ledet.com/margulis/PP7_Ch02_ByTheNumbers.pdf

                        Tom, read and play with the above words of wisdom in the Dan Margulis PDF - it is all there in the theory of how to evaluate and correct.

                        It should not matter about varied colour castes. If each image can have global levels or curves applied which set neutral white/black/grey points in the image - then you are off to a good start (presuming the image has these target points). Memory colours are a bit harder, but there are some easy rules (blue sky, green grass, skintones etc).


                        Regards,

                        Stephen Marsh.

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                        • #13
                          Stephen,

                          After reading the Dan Margulis article, I am reminded of "the devil is in the details."

                          Catia

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                          • #14
                            Here's my take. I didn't do any heavy lifting and I used photoshop elements.

                            I was on a "gradient map" kick, so I found a brownish gradient and applied that. Then I used the gradient tool with a simple black-white gradient on the sky portion of the mask in the gradient map layer.

                            Next I did a levels adjustment layer but everything was looking pretty washed out, so I added a brightness/contrast adjustment layer and once again used the gradient tool to mask the sky area.

                            My effort won't win any awards, but it would meet my needs.

                            Margaret
                            Attached Files

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                            • #15
                              Tom,

                              That's a gorgeous photograph.

                              I'm sorry, I dont have the exact numbers, but basically this is what I tried:

                              - I added a levels adjustment layer and moved the shadows lever to the right to add some depth. I then forced some more brightness even though the historogram didnt indicated a need for it by moving the brightness lever to the right. I then tweaked it a bit using the midtones lever.

                              - This still left a bluish tone to the photo, so I measured using info palette and the eyedropper and adjusted the colors indicated there in the highlights and midtones.

                              _ The sky then looked a bit too yellow so I went into the layer mask in the above mentioned color adjustment layer and made a soft edged selection of the sky and filled it with black to remove the color adjustment from it.

                              - With the selection of the sky still active, I used color balance from the Image menu/adjustments to tweak the sky a bit. It is still a bit off to me, and if I had time I would really mess with it more.

                              Hope that is even a bit helpful!

                              Pam

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