Using single Color Channels of the Tone Curves

Using single Color Channels of the Tone Curves

This post was updated on July 27th, 2019

Adobe ® Lightroom’s Develop Module explained

In the last article of this series, we explored the RGB Tone Curve. Now it is time to examine what we can achieve by using the Red, Green, and Blue Color Channels of the Tone Curves.

Working with single color curves

Working with single color curves means that you are addressing the Reds, Greens, and Blues separately, one at a time. However, it does not mean that you cannot change all three of them for one photo – you can even change all three color curves, and the RGB curve separately since they have different effects on your image.

We have a look at how to achieve the following:

  • Fine tuning the color balance in an image
  • Creating a cross-processed look

Fine tuning the Color balance

Because you can address the Red, Green, and Blue separately in your Tone Curve by choosing the respective Color channel, you can manipulate the Color Balance.
When you change the Color Balance with Temperature and Tint in the Basic Panel, you are addressing the entire image. Changing the Color Balance with the Tone Curve, however, enables you to address only certain areas, or the entire image. With the Color Channels of the Tone Curve, you are now able to increase the warm tones in the shadows, and decrease them in the lighter sections, for example.

Digital Color Wheel

To effectively use this tool, you need to remember the digital color wheel. It combines the RGB model (monitors) and the CMY model (prints) into one color wheel of six primary colors.

Digital Color Wheel combining the RGB color wheel with the CMY color model
Digital color wheel

As you can see in the color wheel above, Red now is the opposite of Cyan, so decreasing Red means adding Cyan, while adding Blue means decreasing Yellow. 

Modifying the Color balance

In the following example of a sunrise over the Alexander Nevsky Cathedral in Sofia, I want to achieve a slightly warmer look. For this I am increasing the reds and decreasing the blues in the image.

Increasing the Reds

Alexander Nevsky Cathedral with an non-altered red and blue tone curve - Using single color channel Tone Curves - After exploring the RGB Tone Curve, it is now time to examine what we can achieve by using the Red, Green, and Blue Color Channels of the Tone Curves.
Alexander Nevsky Cathedral, Sofia – Original Tone Curve
Altered Red Color Tone Curve
Red color curve

As you can see, my changes in the Red curve have an effect on all areas of the photo. The result of this looks like the following image:

Alexander Nevsky Cathedral at sunrise with a slightly increased red tone curve - Using single color channel Tone Curves - After exploring the RGB Tone Curve, it is now time to examine what we can achieve by using the Red, Green, and Blue Color Channels of the Tone Curves.
Increased Red Channel

If you compare the initial photo with the one where the reds are increased, you can spot the difference in the color of the stones of the cathedral. This makes for a slightly warmer look of the image.

Decreasing the Blues

In a second step, I am now slightly decreasing the blue tones in the photo by changing the Blue Color Curve as follows.

Changes made to the Blue Tone Curve
Changes made to the Blue Channel

This makes for a subtle change of the overall look.

After increasing the Red and decreasing the Blue channel - Using single color channel Tone Curves - After exploring the RGB Tone Curve, it is now time to examine what we can achieve by using the Red, Green, and Blue Color Channels of the Tone Curves.
After increasing the Red and decreasing the Blue channel

Compare the three images directly to notice the changes.

Depending on where you change the graph, you increase/decrease a color in the Shades/Darks/Highlights/Whites. So if your Lights are a tad green, you could decrease the greens in the third vertical section of the Tone Curve, effectively adding Cyan to the Lights section of your photo.

Create a cross-processed look

In the old days of analog photography there were two types of color films, color negatives, and color transparency or color slide films. Both were developed using different chemicals. Cross processing means using the chemical for the slide film to develop the color negative or vice versa. Since we are now using digital photography, we don’t need to worry about the chemicals anymore. However, with Adobe ® Lightroom’s Color Tone Curve we can still create that particular look of a cross-processing.

I started with this photo of a Crane’s bill:

Using single color channel Tone Curves - After exploring the RGB Tone Curve, it is now time to examine what we can achieve by using the Red, Green, and Blue Color Channels of the Tone Curves.
Original Color Channels

Changing the Blue Channel

First I am moving the Black Point in the Blue Curve a little bit upward, to reduce contrast and add blue to the shadows. The resulting Blue Channel looks like this:

Adjusted Blue Channel
Adjusted Blue Channel

The result looks like this:

Crane's bill with adjusted blue channel - Using single color channel Tone Curves - After exploring the RGB Tone Curve, it is now time to examine what we can achieve by using the Red, Green, and Blue Color Channels of the Tone Curves.
Crane’s bill with adjusted blue channel

Adjustments to the Red Channel

Then I create an S-curve for the Red Channel, this increases the contrast in the reds and adds a magenta color cast. 

Tone Curve for the changes in the Red Channel
Tone Curve for the changes in the Red Channel
Crane's bill with adjusted red and blue channel - Using single color channel Tone Curves - After exploring the RGB Tone Curve, it is now time to examine what we can achieve by using the Red, Green, and Blue Color Channels of the Tone Curves.
Crane’s bill with adjusted red and blue channel

Making changes to the Green Channel

Finally, I am creating an S-curve for the Green Channel as well. This curve is as similar to the one in the Red channel as I can get it. Of course, this increases the contrast in the greens and adds a green color cast. If the Red and Green channels curves are equally steep, the magenta and green casts cancel each other out. This, because magenta and green are on opposite sides of the digital color wheel.

Tone Curve with changes for the Green Channel
Tone Curve with changes for the Green Channel

The final photo looks like this:

After adjusting all three color channels - Using single color channel Tone Curves - After exploring the RGB Tone Curve, it is now time to examine what we can achieve by using the Red, Green, and Blue Color Channels of the Tone Curves.
After adjusting all three color channels

You can achieve a similar effect, if you, instead of, moving the black point of the Blue Channel upward, create an inverted S-curve, like you would do for an Astrophotograph. 



All trademarks and copyrighted items mentioned are the property of their respective owners.

I am in no way affiliated with any of the products used in this post-processing process. I do not receive any kind of compensation for this article, it was neither offered or asked for.

THIS BLOG ARTICLE “Using single Color Channels of the Tone Curves” IS NOT AUTHORIZED, ENDORSED OR SPONSORED BY ADOBE SYSTEMS INCORPORATED, PUBLISHER OF ADOBE ® LIGHTROOM

All photos taken by Lille Ulven Photography.

Leave a Reply

Your email address will not be published. Required fields are marked *

Social Media Auto Publish Powered By : XYZScripts.com
%d bloggers like this: