In this age of visual effects and computer generated green hulks smashing aliens around New York you would not think that it’s worth to waste even a single word on making an image Black and White, would you?
Simply desaturate with Command-Shift-U and go.
As it turns out, however, there are many (and I mean many) ways to create a black and white image from a color one, and each method gives different results.
I have selected this image as an example because the girl’s tops are in bright, easily recognizable colors, and actually in very pure colors. Pure colors are those where we see the biggest difference for each one of the desaturation techniques we are going to examine.
First of all, the most common method: select the Hue & Saturation Adjustment filter and bring the saturation slider all the way down to zero.
Or use the shortcut for the shortcut: instead of command-U do command+shift+U, no window will open and the image will be desaturated.
As expected the image will become black and white, let’s have a look at the result.
Now for something entirely different, and more recent. The Black & White filter (Command-B) that was created to solve the issue above (yes the image above has an issue even if it’s what most people do).
Can you spot the differences? Especially the girl with the magenta top at the right looks bright now, instead of the dull and muted tone it had in the previous version. The same holds true for all the complementary colors: cyan and yellow.
But wait, that’s not all. Once upon a time, when the Black and White filter was not in Photoshop, a common trick for those that knew better was to convert the image to Grayscale, then convert it back to RGB.
Does this still work? Yes.
Is there any benefit? Maybe.
When you try to convert to grayscale, now Photoshop warns you that the new Black & White filter will take care of the conversion. (If you don’t see this warning, you probably checked the “don’t remind me of this” box.)
Yet, converting to grayscale creates an even different result. This:
The magenta top is now halfway between the desaturation and the Black & White. All other vivid colors have slightly different tones and to me this is still the most natural look.
But wait! There’s another option available!
Convert a copy of the image to LAB color space, go to channels and select the whole frame in the Lightness channel. Copy it, then go back to the original image and paste it. Have a look at the result, it’s different from all three above:
Comparing the four images, I’d say this is really the one that looks most natural. Bright colors are still bright in black and white, and I can safely assume the rightmost girl in the front row is wearing a reddish top even if the image has no color of its own.
Which one to use? Well, for sure, don’t use command-shift-U! It was old before dinosaurs became digital.
I’m partial to the LAB method but the Black and White filter can provide much of the same results without any copying or pasting, so it’s up to you (and your client’s deadline).
Pro tip: most clients can’t distinguish a black and white image from a dishwater so don’t obsess on this.