Sometimes, I like to turn things upside down by asking students to bring in their own images, challenging me to correct them on the fly for the class. The exercise is revealing, because even though I specifically ask for RAW files, at least 50 percent of what I get will be RGB files in TIF or JPEG format. This tells me that there’s still a huge gap in understanding, and I feel pretty strongly that until you really study the controls and practice them on a variety of images (mostly RAW), you’ll never really know how much you’re giving up when starting with JPEG.
My article in the May/June 2014 issue of DPP, "What Is A RAW File?" goes into great detail about how raw image data is stored and should help to explain this slightly difficult concept. In it, we saw how Exposure Values in a scene are compressed into the Lightroom editing space using a process known as tone mapping. Tone mapping compresses the exponentially increasing values of light found in the real world into tonal relationships that we recognize as a photograph. That’s a mouthful, I know, and understanding why tone mapping is necessary is worth the effort. After all, this is what the science of photography is: how you map the giant range of tones out there in the real world into a representative image that you can hang on your wall.
And so, that’s why we want to start with the raw data. The reason you have so much more flexibility when starting with RAW is because you’re shaping it before it’s tone mapped into RGB. Choosing a white balance, setting your white point, black point and basic tonal distribution are all much better when performed on raw data. And that’s what’s absolutely unique about the first eight controls in the Basic panel. These controls are operating on the raw data in its native, linear space.
Take White Balance, for example. White Balance is the set with the first two controls in the Basic panel, and it’s generally the first thing I’ll approach when correcting a photo (Figure 1). When you shoot RAW, you have all the colors of light the camera was able to capture in the original scene, completely unprocessed. So setting a white balance in-camera is entirely unnecessary. When you adjust white balance in RAW, you’re literally scaling the red, green and blue channels separately to create a neutral balance in the linear grayscale data. When you’re shooting JPEG, the camera must assume a white balance for the conversion, and if that assumption is off by much, the resulting color cast will be almost impossible to fix (Figure 2).
The flexibility you have in color correction in RAW is a large part of the benefit. And the flexibility you have in tonal correction using the next six controls are just as great, if not greater.
Exposure and Contrast are your first line of attack when you begin fine-tuning a photo’s basic tonal distribution. And just like White Balance, the Basic tone controls are being applied to the raw luminance data before it’s tone mapped into Lightroom’s RGB working space. Exposure changes move the scene’s captured Exposure Values up and down together, preserving their original relationship to each other. This is why Exposure units in Lightroom are measured in stops, just as they are on your camera. Meaning, if you move Exposure up two stops in Lightroom, the relative brightness in the mid-tones will be exactly the same as if you opened up two stops in the camera. Likewise, moving Exposure down two stops in Lightroom will give you mid-tone values that would match those obtained by decreasing exposure in the camera by the same amount. Of course, clipping points change with exposure changes in camera. But for pictures that don’t clip and fit within the camera’s dynamic range, changing Exposure in Lightroom looks identical.
Contrast is easy to understand, but I always like to compare it to changing contrast with the Tone Curve, because that makes it even more graphic. (It helps people understand how the Tone Curve works, too.) Pushing Contrast up is nearly identical to making a basic S-shape with the Tone Curve, pushing Lights up and pulling Darks down. Increasing Contrast pushes tones away from the middle, making values that are already above the 50 percent mark even brighter, and making tones that are less than 50 percent even darker. Negative Contrast values do the opposite, pulling tones in toward the middle.
So, Exposure and Contrast are pretty easy. Highlights, Shadows, Whites and Blacks solve different problems, and are the most frequently misunderstood. The first thing to notice about these four controls is that they all start in the middle. Moving any one of them to the right makes some part of the tonal range brighter, and moving any one of them to the left makes that part of the range darker. But just saying that doesn’t help you know when to use one rather than the other, so perhaps this will help: In general, the Highlights and Shadows controls are used to recover highlight or shadow tones, while Blacks and Whites are used as clipping controls. And this is an important distinction, because all four controls can go either direction. But as I said, in general (meaning probably 95 percent of the time), Highlights will be pulled to the left (negative values) for bringing highlight details down into play, while Shadows will be pushed to the right (positive values) to open up your shadows.
To get a better understanding of how these next controls work on various tones, I recommend making or finding a simple 10- or 20-step grayscale, importing it into Lightroom or Camera Raw and watching the histogram as you push things around (Figure 3).
Even though the step wedge file is already tone mapped (starting out in a gamma 2.2sRGB or Adobe RGB space), in most cases, it will show you exactly what would be happening to those values in RAW, too. The minor difference will be the way clipping behaves, but for most purposes, using a grayscale or RGB file will be a very close approximation of how RAW values act. (I can only guess that maintaining this symmetry between RAW and RGB was no small feat for the Adobe engineers.)
Once you’ve adjusted the basic tonality of your picture with Exposure and Contrast, the Highlights control gives you the ability to bring very bright highlight details down into play without affecting overall brightness. But the effect of the Highlights control is more complex than what you might think at first, and this is where the stepped grayscale will help make things clear. Not only does Highlights spread out and darken highlight tones, but it enhances highlight detail by adding a special sauce that I call edge enhancement. This enhancement is sort of like sharpening with a large radius, and looks very much like Clarity, only just in the highlights. Load up your grayscale, pull Highlights down to the left and watch the tones become more distinct. Using Highlights in this direction increases contrast
along tonal boundaries the same way sharpening does, only with a wider halo. You’re getting better highlight differentiation both from the edge enhancement and because the tones are being spread apart as they’re pulled away from clipping.
So if pulling Highlights back to recover highlight detail is the 95 percent case, what does it do when pushed to the right? Pushing Highlights to the right into positive numbers appears to do something vaguely similar to pushing Whites in that direction, at least until you do it with the grayscale. And this is where many users confuse the two. Pushing Highlights to the right does make your highlights brighter, and can be used to gently increase contrast. But 95 percent of the time, what you’re probably looking for is a better white point, with a real increase in contrast across more of the tonal range, which is what the Whites control is there for. Besides, pushing Highlights to the right does the exact opposite (of pulling it to the left) when it comes to that edge-enhancement thing: It softens edge definition. There are times when I need brighter highlights, but without the fairly strong contrast increase that comes along with setting a white point with the Whites control. When I want that softening of detail that comes along with the reverse-edge enhancement, I might push Highlights to the right a little. But it doesn’t happen very often—maybe only 5 percent of the time.
The Shadows control works just exactly the same way as Highlights, only going the other direction, and on the other end of the tonal scale. Pushing Shadows to the right opens up your shadow tones and makes them more distinct by not only expanding them toward the middle tones, but also by adding the secret sauce of edge definition. And again, pushing Shadows to the right will be the 95 percent case. There may be times when you want to darken Shadows a touch, in a very gentle way, and without increasing contrast as much as using Black would give you. So this control is almost always used to the right, to "bring some light" into the shadows (Figure 4).
Whites And Blacks
If Highlights and Shadows are mirrors of each other, then so are Whites and Blacks. These two controls are primarily used as clipping controls in their respective "normal" directions, and would be used in the counter direction even less often than Highlights and Shadows. In my workﬂow, the 99 percent case is that Whites will be used to set the white point by pushing it to the right, and Blacks is used to set a black point by pulling it back into negative numbers.
There are two things that distinguish Whites and Blacks from Highlights and Shadows. First, Whites and Blacks are generally used to increase contrast by setting a white or black point, and they do that by stretching out the entire tonal range from one end or the other. But be careful! If you judge the range of the effect by the highlighting that you see on the histogram for each control, you might be fooled into thinking the ranges for Whites and Blacks are much more narrowly focused than that. The tonal expansion is concentrated at one end, but these controls affect the entire range, stretching tones out in a way that reminds me of the way a rubber band stretches. One end is pinned down and doesn’t move, with the rest progressively stretching out and expanding from there.
The second distinguishing feature is the most important, and that’s how these two controls clip tones. When you push Whites to the right, it stretches out all the tones, and when they get to the end, it doesn’t hesitate at all to throw some of them over the edge! And this is exactly what clipping is all about. Remember, we said that pushing Highlights to the right (opposite from the "normal" direction) gently increases the brightest values, but it still leaves you with a gentle roll-off into pure white, preserving Lightroom’s already very natural film-like look. Pushing Whites to the right results in a much stronger effect, making it the best tool for clipping unwanted highlight detail and preserving maximum contrast. The same is true of Blacks (Figure 5). The 95 percent case for Blacks will be pulling it back into negative territory, increasing contrast and acting as a clipping control to set an effective black point.
Find George Jardine’s extensive collection of tutorials at his website, mulita.com.