Converting Color Photos To Black And White With The 'Luminosity' Layer Blend Mode

So far in our look at the various ways to convert a color photo to black and white in Photoshop, we've seen how to change a photo's color mode from it's normal "RGB" mode to Grayscale mode, and we've seen how to completely desaturate the colors in the image using a Hue/Saturation adjustment layer. In this next tutorial, we're going to examine another simple way of converting color to black and white, this time using one of Photoshop's Layer Blend Modes - "Luminosity".

I'll use the same photo in each of these black and white conversion tutorials for the sake of consistency. Here's the photo I'll be using once again:

The first thing we need to do with this method of converting a color photo to black and white is to create a new layer in our Layers palette. Here's what your Layers palette should look like at the moment:

Currently, the Layers palette contains only one layer, which Photoshop names 'Background' by default.

We need to add a second layer, but the trick is, we need to add it below the Background layer. Normally, when you create a new layer, Photoshop adds it above whichever layer you currently have selected in the Layers palette, which is not what we want. Also, if you read the section on the Background layer, you know that Photoshop doesn't allow any layers below the Background layer. After all, it's the background layer. It doesn't make sense to place anything behind a background, since you'd never see it.

So, our first dilemma is that we need to figure out a way to place a layer below the Background layer, which Photoshop won't allow us to do. At least, it won't allow us to do that while the layer is named 'Background'. If we rename the Background layer to something else though, Photoshop no longer sees it as a Background layer. It becomes a normal layer without any of the restrictions that Photoshop places on Background layers. So the solution to our dilemma then is to simply rename the Background layer to something else.

The easiest way to do that is to simply double-click directly on the word "Background", and Photoshop will automatically rename the layer "Layer 0".

Now that we've renamed our Background layer and it's now a normal layer, we need to solve our second problem, which is that we need to add a new layer to our document, but we need it added below "Layer 0", and by default, Photoshop will place our new layer above it in the Layers palette. Fortunately, there's a great little keyboard trick for doing exactly what we want.

We're going to create our new layer the way we normally would, by clicking on the "New Layer" icon at the bottom of the Layers palette. But before we do, here's the trick. Hold down the "Ctrl" key (Win) or the "Command" key (Mac), and then click on the "New Layer" icon in the Layers palette. This little trick tells Photoshop to place our new layer below the layer we currently have selected in the Layers palette rather than above it.

By default, Photoshop will name the new layer "Layer 1", and thanks to our little keyboard trick, will place Layer 1 directly below the layer with our photo on it.

Normally, you'd want to rename your layers to something more appropriate than "Layer 0" and "Layer 1", but for the sake of this tutorial, I'll just leave them with their default names.

Notice that in the thumbnail preview area for "Layer 1" in the Layers palette, it looks as if the layer is filled with a checkerboard pattern. The checkerboard pattern is what Photoshop uses to represent transparency, and what this is telling us is that our new layer currently has nothing on it. It's completely transparent. We need to change that, so we're going to fill it with white.

First, press the letter "D" on your keyboard, which will set your Foreground and Background colors back to their defaults of black and white, respectively. You can see this in the Foreground and Background color selection boxes in the Tools palette:

With our Foreground and Background colors set to their defaults, make sure the new "Layer 1" layer is selected in the Layers palette. It will be highlighted if it is. If it isn't selected, simply click on it to select it.

We want to fill this layer with white, which is now our Background color, and the quickest way to fill a layer with the Background color is by using the keyboard shortcut "Ctrl+Backspace" (Win) or "Command+Delete" (Mac). Go ahead and use the keyboard shortcut to fill the layer with white.

Next, click on the layer with the photo on it in the Layers palette to select it. Here's where we convert the color photo to black and white by changing the layer's "blend mode". By default, the blend mode is set to "Normal", which you can see up at the top of the Layers palette inside the Layer Blend Mode selection box.

We want to change the blend mode from "Normal" to "Luminosity". The Luminosity blend mode is going to give us the effect of removing all of the color from the photo and leaving behind only the luminosity values, meaning the lights, darks, and everything in between. I said it gives us the "effect" of removing all the color because blend modes don't physically change an image in any way. It's more like a live effect, and it's an effect that can be changed at any time simply by changing the blend mode to something else. The actual pixels in your image are not being permanently harmed in any way.

To change the blend mode from "Normal" to "Luminosity", simply click on the down-pointing arrow to the right of the selection box, which will bring up a list of all the blend modes we have to choose from. You'll find "Luminosity" at the very bottom of the list. Click on it to select it.

As soon as you change the blend mode to "Luminosity", your photo will change to black and white.

There's one more step you can take here if you find that your black and white photo is either too light or too dark.

First, we need to marge our current two layers together. With the photo layer selected in the Layers palette, use the keyboard shortcut "Shift+Ctrl+Alt+E" (Win) or "Shift+Command+Option+E" (Mac), which will do two things - it will create a new layer above the photo layer, and it will take the contents of our two existing layers and merge them onto this new layer. In the thumbnail preview of the new layer in the Layers palette, you'll see the black and white version of the photo, which is a combination of the original photo layer set to the Luminosity blend mode and the layer below it that's filled with white.

If you look closely at the screenshot of my Layers palette above, you'll see that I've gone and made a couple of extra changes. First, I've changed the Blend Mode of my new merged layer to "Multiply" by choosing "Multiply" from the list of blend modes, and I've changed the Opacity value directly to the right of the Layer Blend Mode selection box to 30%.

By changing the merged layer's blend mode to "Multiply", you effectively darken the image, so if you find that your black and white version of your photo looks too light, set the blend mode of your merged layer to Multiply. You'll probably find that it's now too dark, so reduce the Opacity value to lessen the effect to your liking as I did.

If, on the other hand, you find that your black and white version looks too light, rather than using the "Multiply" blend mode, select the "Screen" blend mode. "Screen" is the exact opposite of "Multiply" and will lighten your image rather than darken it. Again, if you find your image is now too light, reduce the Opacity value to lessen the effect.

Here's my final version of my color photo converted to black and white using the Luminosity Blend Mode, and after merging the contents of my layers onto a new layer above them and setting the blend mode of the merged layer to "Multiply", with an Opacity value of 30%:

And that's our look at how to convert a color photo to black and white using the Luminosity blend mode. Next, we'll look at a very similar way of converting to black and white, again using the Luminosity values in the image, but this time by converting our photo to the "Lab" color mode.