Black and white conversion can be a complicated ordeal, and you can find yourself down a deep rabbit hole of theory if you're not careful. There are times where that kind of in-depth analysis is critical to a perfect image, but sometimes you just need a quick fix. That's where this tip comes in.
The first time I thought critically about black and white conversion was at Photoshop World in 2010. Nikon Ambassador Vincent Versace had an entire class dedicated to converting and printing black and white images, and it was intense. He's since released a similar hour-long video on YouTube on the same topic if you want to look under the hood at a master's workflow.
For the more fast-paced studio, a quick approximation is often a more practical approach, at least to get started. This is my favorite method of converting, and while it's not perfect for every image (no single technique is), it's saved countless hours over the past few years.
Here is the image we'll be working from (note: I always do my retouching in color before converting to black and white).
Don't Just Desaturate
Before we dive in, I have to briefly mention my biggest pet peeve in monochrome conversion: desaturation. It's almost never the best method, it makes images look muddy and flat, and it takes more time than the method I'm about to show you. This is that same image with the saturation dropped to 0%.
We can do better without taking any more time!
The Gradient Map
The gradient map adjustment layer is a robust tool for color grading and correction, but it's also my favorite method to create a rich black and white. It takes your foreground and background colors and maps each pixel of the image to it's relative value between those two colors. If you have blue as your foreground and red as your background, your shadows will go blue, your highlights will go red, and your midtones will fall on the continuum in between.
This method requires one keystroke and one click. First, set your foreground and background colors to their default (pure black and pure white) by pressing the D key.
You can also click the little mini swatch icon above the foreground and background swatches, but that would make this a two-click tip, and I'm a man of my word. When I say one click, I mean it.
Next, jump over to your Adjustments panel and click the little gradient icon to create a Gradient Map layer.
That's it. The result is dramatically better than simple desaturation! The shadow tones are rich and dark, the highlights are bright and punchy, and the dynamic range of the overall image is as wide as the original. Even better, this method protects your shadows from going too black and your highlights from getting too bright since it isn't modifying them at all. That means you'll retain detail in both areas exactly as they are in your original image.
I'll be honest, I didn't hand pick this sample image because it is tailor-made for this processing method. I just grabbed the first image I saw that I thought would be interesting. It works beautifully on a wide range of images from portraits to landscapes.
Taking It Further
This is by no means the be all and end all solution for all black and white converting. Even in the samples above, I would probably revisit them with some additional dodging and burning or a curves adjustment layer to get them exactly how I want them. Still, I haven't found another method yet that gets me a better starting point than the simple gradient map.
Try it on your own images and post the results in the comments! Just please don't show your clients every image in color and black and white. That's an article for another time.