PHOTOSHOP COLOR CORRECTION: EXTREME COLOR CAST

Transcription

1 PHOTOSHOP COLOR CORRECTION: EXTREME COLOR CAST Projects Overview This project is intended to follow the Photoshop Color Correction Fundamentals course. I ve designed it with the assumption that you understand and have worked your way through the concepts and tools presented in the fundamentals course. The movies in this project are designed to provide you with a start-to-finish workflow for correcting an image that has a specific image challenge. Movie 1 is devoted to evaluating the image and defining the challenge. Movie 2 discusses the tools that will be used to correct or adjust the image. Movie 3 demonstrates step-by-step solutions to the challenge. Movie 4 is an optional movie that shows further enhancements or s that may be made to the image. There are several short courses in the Photoshop Color Correction series. I have carefully chosen each of the Photoshop Color Correction projects because they represent color correction challenges that you will commonly encounter. If you understand the challenges, tools, and techniques, and work your way through each of the challenges and solutions presented here, you should have a substantial arsenal of image evaluation and skills. Extreme Color Cast Project 1. Before and After Here you ll see the starting image and the final image, so you can see where we begin and where we re headed. Original image with strong blue-green color cast. Finished image with strong blue-green color cast removed. Page 1 of 5

2 2. Image Evaluation Our starting photo, of a whitetip reef shark I photographed while diving the Great Barrier Reef off the east coast of Australia, has an extreme blue-green color cast due to the absorption of warm wavelengths (reds and oranges) of light by the hydrogen bonds in the water. And as you might suspect, the deeper you go the greater the absorption and resultant color cast. Viewing the master (RGB version) histogram, we see the overall distribution of tonal ranges from the near highlights to the three-quarter tones. So, we could create a bit more contrast by spreading out/darkening the images s tonal data into the shadow areas. Histogram with master RGB tones displayed showing no image data from the 3/4 tone to shadow. 3/4 tone shadow data that could be darkened to increase contrast Highlight end data that already has a small spike so should not be lightened too much Note: The highlight end of the master histogramalready has a small spike so we should not adjust/lighten the highlight end of the master curve much at all, at least not when using the Master RGB channel. See the individual channel below! But the real story and challenge of this image can be seen when we examine the red, green, and blue channel histograms, either viewing them individually or examining how they overlap slightly in the full color version of the master histogram. We can clearly see the offset to the far right of the blue histogram in relation to the green, which is in turn offset from the red histogram. This offset of the blue and green histograms clearly shows the blue-green color cast in this image. So we have a two-part opportunity with this image: first, and primarily, to remove the strong blue-green color cast, and second, to improve the overall contrast of the image. Histogram with individual channels and color master channel displayed showing large offset of the blue (most offset) and green histograms to the right of the red histogram, indicating a significant blur-green color cast. Page 2 of 5

3 3. Tool Options and Approach The primary tool we will be using to accomplish this will be a Curves layer. Both s neutralization and contrast enhancement can actually be performed simultaneously by performing highlight and shadow s on the individual red, green, and blue channels. Note: We could use a Levels layer to adjust the highlight and shadow points. Curves layers, however, allow us to also make s to any of the data located between the highlights and shadows, on either the individual channels or the master channel. This is where the real power of Curves becomes apparent: the ability to make s anywhere along the tonal range of an image. 4. Adjustment: Neutralization and Contrast Enhancement, Step by Step Create a Curves layer and sequentially activate the red, green, and blue channel curves. On each channel, drag the highlight and shadow sliders to the left and right respectively, until they meet the first uptick in data on the highlight and shadow ends of the individual channel histograms. (Monitor the highlight and shadow ends of the histograms to make sure no peaks form against the highlight or shadow end walls.) Adjustment note: You will move the highlight end of the red channel slider the most and the blue slider the least (in fact not at all). Conversely, you will move the shadow end slider of the blue channel the most and the red channel slider the least. Starting red channel curve Add a Curves layer Finished red channel curve Page 3 of 5

4 Shortcut note: You can use your left and right arrows to move the highlight control point as you monitor the impact of the in the Histogram panel. Note that the start of the highlight data and end of the shadow data in the histograms now line up. The result is that the image is mostly neutralized; that is, most of the blue-green color cast has been removed. Note: The of the highlight and shadow sliders significantly improves both the contrast and color in the image. Nearly all of the blue-green color cast is removed. However, you can do even more if you want to fine tune this by also adjusting the overall brightness and contrast of the image using the master curve! Note: This next brightness and contrast is best performed AFTER your have made your color s using the individual color channel curves s. Starting green channel curve Starting blue channel curve Finished green channel curve Finished blue channel curve Page 4 of 5

5 5. Adjustment: Overall Brightness and Contrast Enhancement, Step by Step Activate the master RGB channel and place a control point at the middle of the data on the RGB composite histogram curve. Then, while monitoring the highlight end of your histogram to make sure no peaks are created, move this midtone control point up to lighten your image. Now place control points at the quarter-tone and three-quarter-tone areas of the curve. Select and move the quarter-tone control point up and the three-quarter-tone control point down. Move these only 5 to 10%; a little goes a long way here! This creates an S-shaped curve that concentrates data a bit more at the quarter tone and threequarter tone, thereby increasing the contrast of the image. I think you will find this useful in a wide variety of images. Start Finish Quarter-tone Three-quartertone Page 5 of 5