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.
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
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:
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.
This makes for a subtle change of the overall look.
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:
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:
The result looks like this:
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.
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.
The final photo looks like this:
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 ®
All photos taken by Lille Ulven Photography.