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Photoshop LAB Color: Chap. 3

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    jfriendjfriend Registered Users Posts: 8,097 Major grins
    edited September 29, 2005
    Yes, it had too much blue
    DavidTO wrote:
    Great ideas, John.

    I think it looks great, save the fact that I would remove the blue cast on the rocks to the right.

    EDIT: on looking at it again, I think that the rocks on the right and the trail are a bit too magenta? The trail has a bit of blue, too, doesn't it? I haven't measured, just eyeballed. I would bring the magenta back, and maybe go a touch more yellow. I believe that would feel more realistic. Just my opinion :).
    Yeah, I just dialed back the blue with a slight adjustment in the B adjustment layer and it definitely looks better to me now. That's what is so incredible about this technique. It took 5 seconds for me to fix the blue and I knew exactly where to go to do it and there were no other undesirable side effects.

    --John
    --John
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    bugziebugzie Registered Users Posts: 30 Big grins
    edited November 6, 2005
    jfriend wrote:
    Yeah, I just dialed back the blue with a slight adjustment in the B adjustment layer and it definitely looks better to me now. That's what is so incredible about this technique. It took 5 seconds for me to fix the blue and I knew exactly where to go to do it and there were no other undesirable side effects.

    --John
    i'm enjoying these discussions although some of the results are incredibly over saturated.

    some wise advice i once heard. everything you can do it photoshop, do it, but do it by only *half*.
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    ginger_55ginger_55 Registered Users Posts: 8,416 Major grins
    edited November 7, 2005
    OK, I haven't done my homework, that annoys some people.

    But every time I go over to LAB to enhance the green in my vegetation, I get a cyan cast that I don't want.................and I don't know why, or what to do about it. And I don't know where to read about it.

    Sorry, hit me with a wet noodle and ignore this if that seems appropriate, but it has been a continuing problem.

    ginger
    After all is said and done, it is the sweet tea.
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    jfriendjfriend Registered Users Posts: 8,097 Major grins
    edited November 7, 2005
    Some things to try...
    ginger_55 wrote:
    OK, I haven't done my homework, that annoys some people.

    But every time I go over to LAB to enhance the green in my vegetation, I get a cyan cast that I don't want.................and I don't know why, or what to do about it. And I don't know where to read about it.

    Sorry, hit me with a wet noodle and ignore this if that seems appropriate, but it has been a continuing problem.

    ginger
    Several idea:

    If your photo already had a subtle cyan cast to it, the LAB color enhancements may be multiplying it, so the first thing you may want to do is to make sure your white balance is set appropriately.

    If you are doing the LAB technique of pushing in both ends an equal amount, then make sure you are truly pushing them in equal amounts. You can either look at the numbers in the curves dialog or you can make sure your curve line is going through the exact center of the curves dialog.

    If all that is set, then you can tweak the LAB curve to remove the blue cast. Depending on the needs of the photos, there are many possible ways to tweak the LAB curve to remove the blue cast. Here are three techniques you can experiment with:

    1) Pushing the ends in differently on the two sides. Pushing the left end in a different amound than the right end of the curve will enhance one color more than another and can change a cast.

    2) Putting a point in the middle of the curve and pushing that point slightly to the left or right makes a big difference in a cast. In your particular case, a point in the middle of the steepened B curve and pushed slightly to the right will probably take some blue out.

    3) Putting a point exactly in the middle of the curve and leaving that fixed and then pushing the two ends in a different amount allows you to isolate the effect to one color. So, you could fix the B curve in the middle and then steepen just the yellow end of the B curve. This will enhance blue's opposite, leaving blue roughly the same.

    There is no exact formula as it depends upon the needs of the photo and what needs to happen with the other colors, but these are some ideas.
    --John
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    ruttrutt Registered Users Posts: 6,511 Major grins
    edited November 8, 2005
    And, Ginger, please post to the corrent thread to make it a little less obvious how little homework you hve done. Probably Chapter 3.
    If not now, when?
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    DavidTODavidTO Registered Users, Retired Mod Posts: 19,160 Major grins
    edited November 9, 2005
    bugzie wrote:
    i'm enjoying these discussions although some of the results are incredibly over saturated.

    some wise advice i once heard. everything you can do it photoshop, do it, but do it by only *half*.


    Some are. It's a learning curve for all of us. Thanks for posting, and I hope that you continue to add to the discussion!
    Moderator Emeritus
    Dgrin FAQ | Me | Workshops
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    iamagooiamagoo Registered Users Posts: 45 Big grins
    edited November 15, 2005
    Great Ideas
    Thank you all for making LAB so easy to use. I've been using these techniques for the past few weeks and have been able to seriously reduce my processing time with very satisfactory results. Like so many others, I have tended to overdo saturation at first but I'm getting a handle on it. I'm especially thankful for the following additional tidbits:
    1) use shadow/highlight (when necessary) before the LAB work to make L channel adjustments easier. (I was losing too much when I needed to make relatively large adjustments with either shadow or highlight.)
    2) use adjustment layers with a/b channels
    3) "make a seprate curve adjustment layer for each part of the image that I'm trying to make an L adjustment on" Brilliant!
    These are such simple, effective ideas that it may have taken me months to stumble upon myself!
    Thanks again,
    Chris
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