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  • fixing clipped or blown channels

    What is the best way to fix a clipped or blown channel? I am needing to be calibrated right now, but some photogs on another forum have informed me that I have clipped the red channel in this photo. I am not seeing it, but I tried fixing with curves (only to get a green tinge in the midtones... this is a common problem for me which I don't know how to fix) and got the same response. I don't even know where to look or how to tell if it is clipped or blown. Help would be GREATLY appreciated!

    4/52
    Canon Rebel XT and XSi; Canon EF 50mm f/1.8 II, EF 100mm f/2.8 USM Macro, EF-S 18-55mm f/3.5-5.6, EF 28-80mm f/3.5-5.6 II; Canon Speedlite 580EX II
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  • #2
    What post-processing tool(s) are you working with?

    Wulf
    Wulf Forrester-Barker << Sites: blog / flickr >>
    Gear: Nikon D40, Nikon AFS 18-55mm f/3.5 - 5.6G, Nikon Series E 50mm f/1.8, Nikon AF 70-300mm f/4-5.6G, Vivitar 90mm f/2.5 macro, Raynox DCR-250, Lensbaby 2.0k, SB600

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    • #3
      I dont even know what any of that means: but that photo is wonderful.
      I am responsible for what I say; not what you understand.
      adammontpetit.com
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      • #4
        Originally posted by OsmosisStudios View Post
        I dont even know what any of that means: but that photo is wonderful.
        Ditto!
        I think the picture is beautiful!

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        • #5
          I would certainly say it's hard to fix something that you can't see. I personally think the photo is fantastic and the colors look very good. As wulf stated, what software are you using?
          Lori Putman flickr
          ~No one can drive us crazy unless we give them the keys
          ~~Life isn't about waiting for the storm to pass, it's about learning to dance in the rain!
          7D | 300L f/4 IS | 70-200L f/2.8 IS II | 135L | 35L | 100/2.0 | 50/1.4
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          • #6
            Oops! Photoshop CS3
            Canon Rebel XT and XSi; Canon EF 50mm f/1.8 II, EF 100mm f/2.8 USM Macro, EF-S 18-55mm f/3.5-5.6, EF 28-80mm f/3.5-5.6 II; Canon Speedlite 580EX II
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            • #7
              It does look like you might have a very slight red cast to the image, though I don't find it distracting at all. In fact I probably wouldn't have noticed if you hadn't mentioned it. If that's what they were talking about, I would use a curves adjustment layer (in Photoshop) and on the red channel, slide the bottom point just slightly to the right, so the line gets steeper.
              [ԯ] marcus
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              • #8
                I've take a screenshot of the image and opened it in The Gimp. There I was able to use the histogram tool to examine the channels. There are about twice as many pixels on the right hand end in the red channel as there there are blue or green ones but I would have to suggest... so what? There is a lot of white and near white in the image; you would expect some pixels to be jammed up agains the right and the extra level of red ones gives the image its warmth.

                Wulf
                Wulf Forrester-Barker << Sites: blog / flickr >>
                Gear: Nikon D40, Nikon AFS 18-55mm f/3.5 - 5.6G, Nikon Series E 50mm f/1.8, Nikon AF 70-300mm f/4-5.6G, Vivitar 90mm f/2.5 macro, Raynox DCR-250, Lensbaby 2.0k, SB600

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                • #9
                  Is there somewhere I can look on a histogram to see if the channel is actually clipped?
                  Canon Rebel XT and XSi; Canon EF 50mm f/1.8 II, EF 100mm f/2.8 USM Macro, EF-S 18-55mm f/3.5-5.6, EF 28-80mm f/3.5-5.6 II; Canon Speedlite 580EX II
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                  • #10
                    I'm not sure about Photoshop. On The Gimp, you can put the marker at the extreme right and see how many pixels in that channel are set at 255 (max value). The process is probably similar.

                    Wulf
                    Wulf Forrester-Barker << Sites: blog / flickr >>
                    Gear: Nikon D40, Nikon AFS 18-55mm f/3.5 - 5.6G, Nikon Series E 50mm f/1.8, Nikon AF 70-300mm f/4-5.6G, Vivitar 90mm f/2.5 macro, Raynox DCR-250, Lensbaby 2.0k, SB600

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                    • #11
                      Originally posted by hopeandmemory View Post
                      Is there somewhere I can look on a histogram to see if the channel is actually clipped?
                      I'm at work right now but if I'm not mistaken you can do some type of a levels or curves window that will show clipping. I'll pull yours into CS3 when I get home this evening and see if it comes back to me. In CS3, can't a curves window be brought up and a choice for "show clipping"?
                      Lori Putman flickr
                      ~No one can drive us crazy unless we give them the keys
                      ~~Life isn't about waiting for the storm to pass, it's about learning to dance in the rain!
                      7D | 300L f/4 IS | 70-200L f/2.8 IS II | 135L | 35L | 100/2.0 | 50/1.4
                      430 EX, 580 EX II Speedlites

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                      • #12
                        Maybe? I don't know. I have never noticed it before, but I have a tendency to overlook things like that even (or especially?) when I am looking for them...
                        Canon Rebel XT and XSi; Canon EF 50mm f/1.8 II, EF 100mm f/2.8 USM Macro, EF-S 18-55mm f/3.5-5.6, EF 28-80mm f/3.5-5.6 II; Canon Speedlite 580EX II
                        flickr | site/blog | twitter

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                        • #13
                          Originally posted by hopeandmemory View Post
                          What is the best way to fix a clipped or blown channel? I am needing to be calibrated right now, but some photogs on another forum have informed me that I have clipped the red channel in this photo. I am not seeing it, but I tried fixing with curves (only to get a green tinge in the midtones... this is a common problem for me which I don't know how to fix) and got the same response. I don't even know where to look or how to tell if it is clipped or blown. Help would be GREATLY appreciated!
                          It's hard to fix in PS. I prefer to set my camera to show blinkies in the red channel when shooting people.

                          It also looks to me like you've blown the reds in this photo, especially on her left side of her nose. It often looks bad because -- to my eye -- it gives a splotch or some splotchiness of a gross looking yellow. One way to see it is to open up a Levels layer and option-click (on a Mac, no idea on Windoze) the highlight slider. Look for the red pixels near the face. Those are your blown reds. Let go of the option button and look at that area in comparison to the nonblown areas. On a photo of the size you posted, it's there if you look. If you print a bigger version or do some types of color corrections, it often looks bad and more noticeable.

                          The problem is that faces have a natural amount of cyan (blue green) in them. And I think that this cyan helps to form shadows on the face. An un-color-corrected photo in the shade often has a lot of cyan in it -- and you can tell just from the color that it was taken in the shade! Cyan is the opposite of red. So when you blow the reds on a large area of the face (100% red), there is 0% cyan. My theory (untested) is that the (trained) eye picks up on this by seeing the blown area as shapeless and splotchy because there is no subtle shaping of the face there. But I could just be full of sh..!

                          EDIT: I think this is why it's so hard to fix convincingly. You can add cyan back in, but (under my theory) you've lost the information about the shadows that would make it look real. You just gotta be careful when clipping highlights.

                          I had never even thought about blowing the reds until I read Michael Grecco's book in which he describes being very careful to avoid it. Once you see what it does, pictures just look bad with blown reds. And it's right where you want people to look! Now if I blow reds -- as shown by the blinkies on my camera histogram -- I reshoot. Period. Unless it's a once in a lifetime shot, in which I just grit my teeth. I have to close my eyes when looking at those photos!
                          Last edited by ttosifa; 01-21-2009, 09:45 PM.

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                          • #14
                            Other than the possible fixes mentioned above, I've no idea how to fix this. The only input I can add is from my painting days. I was taught to make brown by mixing red and green, so it stands to reason that if you think your reds are blown, and decrease the level, you will increase the other component which is green. Since you have so much brown in your image (which is very nice btw), any adjustment will take you toward green or red. Have you tried adjusting from "Raw", instead of jpeg? You may be able to fix your reds without boosting the greens. Please post whatever fix you find, as this issue may become problematic to other members as well.
                            "Sic gorgiamus allos subjectatos nunc"..."We gladly feast on those who would subdue us". Not just pretty words." - Morticia Addams
                            My Gear: Canon EOS Digital Rebel XSi, Canon 50mm F1.8 II EF lens, Canon 28-90mm F4-5.6 III EF lens, Promaster 70-300 5.6 tele/macro lens, Canon Speedlite 430 EX II, Canon Remote switch, GIMP, and Photoshop CS4.

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                            • #15
                              Just thinking -- one thing you might try is adding a photo filter layer and choosing a cyan filter. This will add cyan to the whole picture. Don't worry about that. If you leave it at the default density of 25, the blown red areas will now have uniformly about 4% cyan. The problem is that it shouldn't be uniform -- it should be lower in the brighter areas and darker in the darker areas, and should mix in gradient fashion with the non-blown parts of the face.

                              So, try adding either a green channel layer mask or a blue channel layer mask to the photofilter layer. Do Image -> Apply Image -> Channel: Green, Blending: Normal (all others default). How does this look in the blown areas? Just worry about the colors on the face. You can adjust the opacity of the photo filter layer, play with curves on the layer mask, etc. EDIT: I can't really tell with the low res image above; you'll need the high res version.

                              The background doesn't look as nice with the extra cyan, so I'd just paint the layer mask black there to get the original.

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