• Welcome to ScubaBoard


  1. Welcome to ScubaBoard, the world's largest scuba diving community. Registration is not required to read the forums, but we encourage you to join. Joining has its benefits and enables you to participate in the discussions.

    Benefits of registering include

    • Ability to post and comment on topics and discussions.
    • A Free photo gallery to share your dive photos with the world.
    • You can make this box go away

    Joining is quick and easy. Login or Register now by clicking on the button

The Cayman Diver Advance Color Correction Tutorial

Discussion in 'Darkroom Tutorials' started by PapaBob, Nov 18, 2006.

  1. PapaBob

    PapaBob ScubaBoard Supporter ScubaBoard Supporter

    801
    2
    18
    If you have used the History Snaps action and clicked on the Mandrake snapshot as shown in the above image, the basic Mandrake adjustment will now be your background layer. Open your Layers Palette. We want to add a Levels Adjustment layer. Adjustment layers are found under the half black half white circle in the middle of the bottom of the Layers Palette. Click on it and select Levels.

    I worked the individual color Channels in Levels. The Red I left alone. The Green I dropped the middle slider a tad. On the Blue I set the left (shadow) slider to the tail of the histogram and adjusted the midtone slider. These were my settings.

    [​IMG]
     
  2. PapaBob

    PapaBob ScubaBoard Supporter ScubaBoard Supporter

    801
    2
    18
    I always watch the image as I am making the levels adjustments. I left the red alone because boosting it would introduce artifacts. The Green Channel did not need much adjustment because this channel had good detail and balance (see above). The Blue Channel adjustment in connection with the Green reduced the blue color cast, improved the reef color and contrast and improved the divers skin tones. Actually if you stop here you can be happy with the result. This is what the image looked like after the Levels Adjustment.

    [​IMG]
     
  3. PapaBob

    PapaBob ScubaBoard Supporter ScubaBoard Supporter

    801
    2
    18
    So, I didn’t stop there. I thought I could still improve a few things. For instance, I wanted to pull some more of the color cast out of the sand. I wanted to improve the flesh tone of the diver. I thought the color contrast in the reef could be improved. Finally, I wanted to give the image a little more tone contrast. These were my steps.

    HUE SATURATION ADJUSTMENT

    After Mandrake and Levels the blues still overwhelmed the image and I wanted to reduce them. I opened a Hue/Saturation Adjustment Layer above the Levels Adjustment Layer. Under the Edit menu in the dialogue box I changed the edit mode from “master” to “blues.” I then selected the + eyedropper (middle eyedropper in the HS dialogue box) and swept it around the sand. If you look at the hue sliders at the bottom of the HS dialogue box you will see that this selects the color range of blues and cyans in the sand. I did not touch the Hue slider and only reduced the lightness a tad but reduced the saturation (now only adjusting the selected blue range) to -50. This reduced the blue cast in the sand without completely eliminating the blue water in the background. This is the result and my HS settings.

    [​IMG]


    And the image after the Hue/Saturation adjustment

    [​IMG]
     
  4. PapaBob

    PapaBob ScubaBoard Supporter ScubaBoard Supporter

    801
    2
    18
    Making adjustments in LAB mode is an entire course in and of itself and cannot be covered in one tutorial. If you are interested in the many wonderful results you can produce working in this color space, then I highly recommend Dan Margulis’ book “Photoshop LAB Color - The Canyon Conundrum and Other Adventures in the Most Powerful Color Space.” The book is one of the best texts for advanced Photoshop I have read. Just be prepared to work at his examples and go over his instruction several times before you start to get the hang of things. It is not for the beginner.

    Dan has several ideas on how to use the LAB color mode to enhance targeted colors without the use of multiple layers and masks to isolate the adjustment (although you can use layers and masks to fine tune the results if you want ... I did not do that here). I will try to give a little background before I show my adjustments.

    In LAB all color is produced along two axis, the “a” Channel and the “b” channel. You can work the channels in Levels or in Curves with Curves giving you the maximum control. You must duplicate the image and flatten the layers before you convert to LAB mode. After you convert to LAB mode (Image>Mode>LAB), bring up a Curves Adjustment Layer and change the Channel to “a” or “b” you will get a box with a diagonal line in it. The center point on the line I call the “gray point” and if you draw an imaginary horizontal line throught the gray point you get the “gray line.” If you have a normal curves set (dark lower left and light upper right) and set the Curves grid to 10 lines per axis rather than 4 (this is just to make it easier to see what you are doing) then the following colors are affected in the “a” channel. Above the gray line are the magentas and below the gray line are the greens. In the ‘b” Channel, above the gray line are the yellows and below the gray line are the blues.

    Global color corrections in LAB are difficult which is why I did as much as I could in RGB before converting into LAB mode. In fact if you always run an “a” or “b” curve as a straight line through the gray point (you don’t bend the curve), then you will enhance but not shift color.

    If you bend the curve above the gray line in “a” you affect magentas and below the gray line the greens. If you bend a curve above the gray line in “b” you alter yellow and below the gray line the blues. Most colors are represented by a blend of the “a” and “b” Channels which makes LAB adjustments tricky. It takes practice to get the hang of it. Working on a Curves Adjustment Layer lets you experiment and you can always go back to your settings if you save as a PSD file.

    I would click on the gray point to set an initial control point and then play with, set and move control points above and below the gray point but close to it. If you move the cursor over the part of the image you want to adjust it will show you where on the curve the color represented by that part of the image is. You can set a control point on the curve by a ctrl-click on the spot in the image you are trying to adjust. You should move the control points straight up or down and can use the up arrow key or down arrow keys to do this.

    All of the tone or “lightness” data is in the “L” channel. The L channel curve allows you to alter the contrast of the image.

    There is a lot of experimentation involved. The following are my LAB adjustments to improve the flesh tone of the diver and the color contrast on the reef and alter the blue background water.

    [​IMG]

    After saving my LAB psd file, I then converted the LAB image back to RGB so I could save a Jpeg file.
     
  5. PapaBob

    PapaBob ScubaBoard Supporter ScubaBoard Supporter

    801
    2
    18
    In review, this is the original image.


    [​IMG]


    This is the result after a Mandrake adjustment.

    [​IMG]

    Then the Levels adjustment in the individual color channels

    [​IMG]

    Then the Hue Saturation adjustment to reduce the blue cast in the sand.

    [​IMG]

    And the final adujstments in LAB color mode converted back to RGB


    [​IMG]


    You could stop anywhere along the way if you liked the result. If you have any questions let me know.

    ¬óBob
     
  6. cayman diver

    cayman diver Instructor, Scuba

    # of Dives: 500 - 999
    Location: Grand Cayman
    85
    0
    0
  7. ScottB

    ScottB Solo Diver

    # of Dives: 100 - 199
    Location: Mendota, Virginia
    283
    0
    0
    Beautiful work Bob... Beautiful.. Thank you so much for the tutorial =)

    Take care and best wishes to you and your family this Thanksgiving and Holiday season as a whole as well =)
     
  8. cfelliot

    cfelliot Manta Ray

    # of Dives: 200 - 499
    Location: Portland, Maine
    577
    10
    18
    Nice! Thank you very much for taking the time to explain this! Great job! :):):)
     
  9. Mike Veitch

    Mike Veitch Dive Charter

    12,431
    399
    83
  10. rje634

    rje634 PADI Pro

    # of Dives: 200 - 499
    Location: NY
    716
    2
    18
    Bob,
    Excellent post on color correction in PS.
    Having finally breaking down and getting PS CS2 your tutorial is a godsend..
    Thank you for posting a tutorial that lets me get the results I'm looking for.

    Thanks again
    Joe

    PS, Bob if you happen to have the whole tutorial in a doc of some other "whole" format I would love a copy. Let me know..
     

Share This Page