The Lightroom Tone Curve is the single most complete tool for editing exposure, contrast and color. Many people avoid it because it’s not immediately understandable unless you are already familiar with the “curves” concept. However, it’s worth learning because it can produce the detailed edits your photo might need.
Once you understand Color Curves, you can use this tool to add creative looks to your photos as well as correct shooting mistakes.
The Lightroom Tone Curve can be found on the right side of the Develop Module. It looks like this, by default:
What we are looking at in the view above is the Parametric Tone Curve. It’s useful, but only slightly more so than the tonal sliders in the Basic panel above it. Essentially, you use those sliders you see to lighten or darken the given tonal region. For example, you could darken the Highlights (the brightest tones in your image) by moving the Highlights slider to the left. Or, you could brighten them by moving that slider to the right.
However, the real power of curves is hidden behind this panel. We’re going to skip right over the Parametric Curve and move to the Point Curve, which is where you’ll find the most detailed control for your edits.
To move to the Point Curve, click on the box in the lower right corner next to the arrow in the screenshot above. It looks like a curve with a point on it – no surprise there!
The point curve looks like the image below. Note that you don’t have the individual tonal sliders underneath it.
There are a few things you should notice as you look at this point curve. First off, you’ll see a white diagonal line that is perfectly straight. In order to edit your photos, you will curve that line – that’s where the name of the tool comes from.
Next, look at the histogram behind the soon-to-be-curved line. That histogram is exactly the same as the histogram at the top of your develop module. If you need a refresher on histograms, remember that they take every pixel in your photo and sort them into 256 degrees of brightness. The very brightest pixels appear on the right side of the histogram; the darkest on the left side. A severely overexposed photo will have most of its pixels on the right side. And a severely underexposed photo will have most of its pixels on the left side.
(Want more info about histograms? Read on, right here.)
We’re going to come back to that histogram shortly. First, I want to point out one last feature of this Point Curve. In my screenshot above, do you see where it says RGB inside the green circle? RGB stands for Red, Green AND Blue. When they are all 3 together, that refer to the “composite” curve. The composite curve changes lightness & darkness only. However, you can click on RGB to select either Red, Green OR Blue. Selecting one color allows you to edit it independently of the others.
Ok, that’s the tour of the Lightroom Tone Curve. Ready to talk about how to use it?
Use the Lightroom Tone Curve to Edit Exposure & Contrast
Let’s start with Exposure & its cousin Contrast. Exposure refers to how bright or dark an image is. When editing with Curves, I look at both the image as a whole and the focal point in particular to determine whether exposure needs adjusting. For this photo, the focal point is the boy – specifically his face. His face is too dark.
To fix it, I click on the Targeted Adjustment Tool of the Point Curve Panel. The TAT is circled in green at the top left corner of the screenshot above. This tool lets you tell Lightroom, “Hey. This point that I’m clicking on needs to be brighter (or darker). Brighten it (or darken it) until I stop dragging my mouse.”
So, after clicking on the Targeted Adjustment Tool to turn it on, I click on the spot that I want to be brighter. In this case, it’s the boy’s forehead. Without releasing my mouse click, I drag up until the photo is sufficiently bright and then release the click. (If I wanted to darken, I would drag down.)
You can see in the screen shot below that:
- The photo is brighter.
- There is a point on the curve. Clicking the photo with Lightroom’s Targeted Adjustment Tool puts a point on the point curve corresponding to the clicked area’s place on the histogram.
- The straight line is now curved. It curves up to indicate that the photo is brighter. The apex of the curve corresponds to the boy’s forehead. The curve would curve down (like the letter U) if I had darkened the photo instead.
This next photo shows you how it would look if I had clicked and dragged on the dog’s ear instead.
The difference is subtle. However, the dog’s ear is slightly brighter in this photo than it is in the edit above, and the boy’s face is slightly darker. The colors in the grass and his shirt are less saturated. The shape of the curve is clearly different.
What about using the Lightroom Tone Curve to adjust contrast?
Unlike exposure, contrast looks at the brightest brights and darkest darks in an image and compares them to each other. A histogram with all of its pixels bunched up in the middle is going to have low contrast, because its darkest pixel isn’t very dark and its brightest pixel isn’t very bright. In other words, their tone is close.
On the other hand, a histogram with lots of pixels on the left and right sides of the histogram is going to have high contrast, because the darks are very dark and the brights are very bright.
To increase contrast using the Tone Curve, you want to create an S-shape. This S-curve makes the brights brighter and the darks darker. The curve curves up on the right side of the histogram, where the brights live, and it curves down on the left side of the histogram, where the darks live.
It looks something like this:
To create this contrast, I kept the forehead brightening point that I added above. I also clicked and dragged down on the dog’s leg to darken the darks. You can see that the image has more pop and even looks a bit crisper. This is what an image with good contrast looks like.
Use the Lightroom Tone Curve to Edit Color
Ok, this image is looking better in terms of exposure & contrast now, but the color is still off. Now, Lightroom has two great white balance sliders that could be used to improve the color in this photo. The white balance sliders adjust these two color pairs:
- Blue and yellow
- Green and magenta
However, these two sliders aren’t as full-featured as the adjustments possible with color curves. With the White Balance sliders, you can’t:
- Adjust the red and cyan color pair.
- Adjust a color just in the darks or in the brights but not both.
Those are both huge benefits of using the point curve to edit color. When I edit, I usually adjust color using the White Balance sliders to the extent that I am able and then move down to the tone curve for photos that need an extra touch.
I find that skin that looks gray or sickly in photos often benefits from adding red using the Tone Curve. Also, shadows tend to soak up colors more noticeably than other parts of the tonal range. I’m going to use both techniques to improve this photo.
First, I set global white balance by clicking with the white balance eyedropper on the fence, which is a neutral gray in many areas. That brings me to this point:
Next, because I want his face to be more “rosy,” I select the Red Tone Curve. After activating the Targeted Adjustment Tool, I click on his skin and drag up very slightly.
Finally, I’d like to neutralize the green reflection caused by grass on his forearm. See that? The arm is shadowed on the underside, and it’s picking up a color cast from the grass. If you didn’t notice it right away, look for these color casts in your own photos. They will start driving you crazy once you learn to recognize them!
To neutralize the green, I went to the Green channel on the Tone Curve. With the Targeted Adjustment tool, I clicked once on the green reflection. Next, I hit the down arrow on my keyboard twice. Using the arrows instead of the mouse is the easiest way to make micro adjustments to your curve.
Why did I use the down arrow? Good question! When you are looking at the Color Curves, each time you move your line up, you increase the color that the channel is named after. When you move the line down, you decrease that color. To neutralize this color cast, we needed to reduce green, so I moved the line down.
Removing the green color cast completes my edit for this photo. Here is a before and after:
Like this tutorial? Read the next one about how to use the Lightroom Tone Curve for creative effects.
What do you think? Does this tutorial make the Lightroom Tone Curve more useable, if you didn’t use it already? What other things do you do with the curve that I haven’t mentioned?