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The Cayman Diver Advance Color Correction Tutorial

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

  1. PapaBob

    PapaBob ScubaBoard Supporter ScubaBoard Supporter

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    Cayman Diver posted the following image with requests for assistance in editing.

    [​IMG]

    I did a quick work through and posted the following result.

    [​IMG]

    I was asked for my steps and offered to post a tutorial.
     
  2. PapaBob

    PapaBob ScubaBoard Supporter ScubaBoard Supporter

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    This is the readers digest version of my steps:

    1. Analyze image. Need to repair dead red channel, do a global color correction. Goal is to improve skin tone, remove color cast from sand, and improve color and contrast in background reef.

    2. Run action that produces Mandrake adjustment without final Autolevels step.

    3. Perform global color correction in the individual RGB color channels using a Levels Adjustment Layer.

    4. Add Hue/Saturation adjustment layer. Change mode from master to "Blues". Sample sand with the +eyedropper. Reduce saturation to remove some of the blue/cyan cast from sand.

    5. Duplicate image. Flatten duplicate and convert to LAB color mode. Add Curves Adjustment Layer. Adjust curves in "a" and "b" channels to improve flesh tone and color contrast in the background reef. Adjust curve in "lightness" channel to improve tonal contrast.

    6. Flatten image, convert back to RGB and save PSD. Separately save the original working image that has the Mandrake adjustment, Levels Adjustment Layer, and Hue/Saturation Adjustment Layer.
    Decide which of the versions you like the best.
     
  3. PapaBob

    PapaBob ScubaBoard Supporter ScubaBoard Supporter

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    INTRODUCTION

    I noticed that it has been a while since I (or anyone else for that matter) has posted a Photoshop tutorial. I promised to check my PSD file and post the steps. Of course nimnutz Bob was in a hurry at the time and forgot to save his PSD. However, it forced me to retrace my steps and I think will make for a better tutorial.

    The goal was to achieve a pleasant result fairly quickly (at least once you are familiar with the techniques used) without resorting to multiple layers and masks. All of the adjustments made use Adjustment Layers. With a little more effort, the results can be refined with masks, but that is not the purpose of this tutorial.

    I have been reading Dan Margulis’ book “Photoshop LAB Color” and he has some suggestions on how to improve underwater images in the LAB color mode. The initial color correction must be done in RGB. If you are lost in the lingo then you have probably figured out that this tutorial will deal with some intermediate to advanced techniques in full version Photoshop. If you are working with Photoshop Elements then this tutorial will not be of much use to you. All of the steps I will present will work in Photoshop version 7 or higher. I have tried to post screen shots and describe my steps so if you are just starting in Photoshop, I hope the presentation will make the steps easier for you to duplicate. Actually, once you get the hang of some of the steps, it will be a lot faster and easier than following this tutorial for the first time.

    About two years ago I wrote an article on using Photoshop to color correct underwater images. You can find the article if you CLICK HERE. It is old but the information still works. Some of the techniques I will be using here. For some reason the html version is missing text. Click on the icon for the printer friendly version and all of the article will be available to read or print. Unfortunately, I was not able to print screen shots when the article was written.

    I also wrote some action files which you can download if you CLICK HERE. One of the actions “Auto History Snaps” I will be using in this tutorial. If you have an action that performs the “Mandrake Method” you can use that. There is a popular “underwater.atn” action file that runs the Mandrake Method but it performs an autolevels as the last step. If you have this action file loaded then copy the action and delete the autolevels step and you will be able to use it for this tutorial. If you need help, send me a PM and I will do my best to assist.
     
  4. PapaBob

    PapaBob ScubaBoard Supporter ScubaBoard Supporter

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    The first step is to duplicate the image and work on a copy. That way you do not accidentally overwrite the original image in case you have to go back to it.

    Next, you want to identify the areas to globally improve in the image. In this case I wanted to pull out color in the reef, make the diver’s skin look more natural, and remove the cyan/blue color cast in the sand and in the image overall. I also find that it helps me to take a look at the RGB color channels in the Channels Palette. Here is what I found.
     
  5. PapaBob

    PapaBob ScubaBoard Supporter ScubaBoard Supporter

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    Like many underwater images, the depth of the shot and the lack of strobe or strobe coverage has produced a “dead red” channel. It is black and has very little image detail.

    [​IMG]

    This channel will need to be repaired or replaced because it does not have enough information to make any adjustments.
     
  6. PapaBob

    PapaBob ScubaBoard Supporter ScubaBoard Supporter

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    Things are looking up. This channel has nice detail and tonal balance. Adjustments to this channel should produce some pleasing results.


    [​IMG]


    Not only does this channel have workable information, it will not need a lot of adjusting.
     
  7. PapaBob

    PapaBob ScubaBoard Supporter ScubaBoard Supporter

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    This channel has some image detail but is very bright and blown out. This is indicative of a lot of blue in the image and we should be able to improve this channel.

    [​IMG]

    The Blue channel will require much more tonal adjustment than the Green channel but it has enough detail to work with.
     
  8. PapaBob

    PapaBob ScubaBoard Supporter ScubaBoard Supporter

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    I like the individual color channels in the Channels palette because it lets you see the image. Another way of checking color information is using the Histogram Palette. Note the Red histogram is smashed to the left (dark) side. The green histogram is spread out in the middle indicating the tonal range and balance in this channel. The blue histogram is wider than the red (tonal detail) but is pushed up to the right indicating bright blue in this channel.

    [​IMG]

    We will see the histograms again in a moment.
     
  9. PapaBob

    PapaBob ScubaBoard Supporter ScubaBoard Supporter

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    I often start work on an underwater photograph by running the “Auto History Snaps” action. This action runs the automatic adjustment functions in Photoshop that often produce a pleasing start out of the gate. After you have run the action you can open the History Palette and click on any of the images to see how a particular function did. This becomes the background layer in the Layers palette if you want to do more work. The History Palette looks like this after running the action.

    [​IMG]

    Actually the Mandrake Autocolor adjustment produces a pleasing image but I thought I could do better with some manual adjustments.
     
  10. PapaBob

    PapaBob ScubaBoard Supporter ScubaBoard Supporter

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    I did not use the Mandrake Autocolor History Snap but started with the Basic Mandrake adjustment.

    The Mandrake method uses information in all of the color channels to reconstruct the Red Channel. David (Mandrake) posted his technique years ago and it remains one of the best methods of repairing the “dead red.” Another method is to use a Channel Mixer Adjustment Layer and repair the Red Channel by hand. Although you get a more precise result tailored to the image, the Channel Mixer requires some practice and is slower than running the Mandrake Action. I selected the basic Mandrake from the History Snaps selection. Again, if you have loaded the Mandrake action from another source (underwater.atn is popular) check to see if it has an Autolevels command at the end of the action. If so, copy the action and delete the autolevels step. You have a lot more control if you run a basic Mandrake and then do the color correction in a Levels Adjustment layer. This frame shows the selection of the basic Mandrake adjustment.

    [​IMG]
     

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