It’s often claimed that white balance has no bearing on black-and-white images. Many basic tutorials recommend using your camera’s automatic white balance because any moderately accurate white balance is fine for an image that will be converted to black and white. This is simply incorrect!
Adjusting the white balance of a digital image is an incredibly powerful way to control how Adobe Photoshop Lightroom interprets the colours in your image when you convert to black and white. In this tutorial, you'll learn how to do just that.
What Is Colour Balance?
When you look at a scene, your brain does a large amount of processing and interpretation of what your eyes see. Regardless of the light falling on it, we will always see a white sheet of paper as white. From a pure physics perspective, though, that white sheet of paper could be reflecting any colour of light; it’s just that we know paper is white, so that’s what we see—or rather, that’s the colour our brains interpret it as.
One of the ways your brain understands that the white piece of paper is white is that it takes cues from the rest of the environment. If the sun is low in the sky and is casting an orange glow across everything, your brain realises this and subconsciously adjusts to accommodate.
If you take a picture of a white sheet of paper lit by a setting sun and view it under fluorescent light, however, your brain won’t have the environmental cues to interpret it as white. You will see it as yellow. This is the core of colour balance. The colours we see with our eyes are only indicative of the colours in the scene; they’re not an accurate interpretation.
Why Colour Balance Matters to Black-and-White Conversions
When we see a photo of a red rose, as long as the colour balance is not completely out of whack, we’ll interpret it as red. If you examine the image in Adobe Photoshop or look at its histogram, you’ll quickly find that the “red” rose involves large amounts of adjacent colours. In the case of red objects, that’s likely to be oranges and magentas.
This means that when you try to control how the red rose is converted to monochrome in Lightroom, you will need to use more than one slider. This is fine as long as there is no other subject in the image that is also controlled by those sliders. Say, for example, there is also a pink rose in the image. The red slider will have a small effect, as will the purple and magenta sliders. It will be impossible for you to control only the red rose without also affecting the pink rose.
When you’re converting to black and white in Lightroom, the software doesn’t care that a rose is red or pink. The only data the program can account for is what the actual, recorded pixel information is. By adjusting the white balance of an image, you can control what information is available for Lightroom to interpret and set the stage for a better conversion.
How to Identify Which Way to Adjust the White Balance
Identifying which way to push the colour balance of the image to isolate a specific colour requires some knowledge of colour theory and a bit of trial and error. With Lightroom’s white balance sliders, you will either add blue, yellow, green or magenta to the image. Each colour will have a different effect on the image depending on what colours are present.
For example, in a mostly blue image, adding blue will intensify the colour, while adding yellow would neutralise it, and vice versa. Which way to adjust the colour balance to isolate an object depends entirely on how the colours are interacting.
In the image above, the red ball is far from red. If you examine it in Photoshop, you’ll find it is actually far closer to purple or magenta. Our brains are just using the context of the image to automatically correct how we see it. Lightroom can’t do that.
In this case, adding yellow is the best way to isolate the ball; it neutralises the blues affecting the ball to a greater extent than the more intense blues in the rest of the image. If the ball was a different colour or less affected by the blue colour cast in the image, adding blue to intensify the colours in the rest of the image might be an easier way to isolate it.
In general, colours closest to the colour you are adding (and its complementary colour) will be most affected. The colours close to it will be intensified, while the colours close to the complementary will be neutralised. For example, in the colour wheel on the right, I adjusted the colour balance significantly towards yellow. The yellows, blues and colours nearby are most affected, while the cyan and red are changed to a lesser degree. In most cases, you wouldn’t use an adjustment as extreme, so the effect on the cyan and red would be even less.
To decide which way to adjust the colour balance in your own images, identify what the main colour you want to affect is. If it’s blue, yellow, magenta, or green, great! Otherwise, pick the one that it is closest to it on the colour wheel. Start adjusting that colour with the white balance sliders to see what effect it has. If it doesn’t isolate the subject as you’d hope, try adding the complementary colour instead. In many cases, you’ll need to use a combination of both sliders.
Colour balance has a lot more effect on black-and-white conversions than many photographers assume. How we see the colours in an image on the screen in front of us and how Lightroom interprets them are two very different things. What looks red to us might be purple to Lightroom. This has important implications when you’re trying to control how Lightroom converts everything to black and white.
With the colour balance sliders, you can better control how Lightroom interprets your image. It might make for an ugly colour image, but it can make it a lot easier to convert the image to black and white by mapping the colours in your image more closely to Lightroom’s Hue, Saturation, Lightness sliders.
Knowing which way to modify the colour balance requires a bit of forethought and a lot of trial and error. It’s best to start with the colour closest to the one you want to affect and then experiment from there. You won’t always need to use this technique but, when you want to isolate a specific colour, it can come in very handy