How to Convert Color to Black and White in GIMP

Tuesday, June 7, 2011  at 6:58 AM
Control how your color photograph is changed into black and white.  Welcome to the fifth article in my Photography Editing in GIMP series!

Previous articles:

Article 1: Easy Photography Editing in GIMP
Article 2: How to Crop in GIMP
Article 3:  How to Control Saturation in GIMP
 Article 4: How to Control Contrast and Lightness 

These tutorials use the free photo-editing program GIMP.  I am not being paid to endorse the program GIMP--I just really like it!
Convert a Photo to Black and White

There are multiple ways to change a color photography to black and white in GIMP.  I will be including the two easiest and most common ways to turn a color image into a striking black and white photograph.

Method 1: Using Desaturate to Change a Color Photo to Black and White

By using the desaturate option, you can change a color photo from this:

Boats in Venice

into this:

Boats in Venice Black and White

Step 1: Open the photo in GIMP.  Under the "Colors" tab, click the Desaturate button.

Boats in Venice

Step 2: Select if you want to Desaturate based on lightness (the shade of the color), based on luminosity (how vivid the color is), or based on an average of the two.  I usually like the output better when I desaturate based on luminosity, but you can preview both and choose the one that you prefer.

Boats in Venice

Step 3: Click OK and save!

Boats in Venice


Method 2: Using Decompose to Change a Color Photo to Black and White

Although the most common way to change a photo into black and white is to use the "Desaturate" tool, that will often strip the picture of fine nuances in tone and you do not have much say in how the shades of gray turn out.  I prefer to use the Decompose option as it allows for greater control over the finished image.

This method can take you from this:

Boats in Venice

to this:

Boats in Venice

Step 1: Open the image with GIMP and select the "Colors" tab, then select "Components" and finally click on "Decompose."

Boats in Venice

Step 2: To make this process a bit easier, we are going to open a new dialogue box that will allow us to see the different layers we are using.  To do this, select the "Windows" tab, then select "Recently Closed Docks" and finally click on the "Layers, Channels, Paths..." option.

Boats in Venice

Step 3: Now that this dialogue box is open, we can use it to see the different layers that the Decompose function has given us.  Basically, the Decompose function has one layer which turned only the red values into black and white, one layer which used the green, and one layer which used the blue.

As you click on each layer in the dialogue box, you can control what that layer does.  Initially, each layer starts off with Opacity at 100%, which means that they are all contributing equally to the final image.  By adjusting the opacity, you can control what makes up the final image. 

Boats in Venice GIMP tutorial

Step 4: If you click on the 'eye' button by each layer in the dialogue box, you can control if you see that layer or not. 

Here is what the dialogue box would look like if I only wanted to see the blue layer:

Boats in Venice GIMP tutorial

Here is what my final image would look like if I only used the red layer:

Boats in Venice GIMP tutorial

Here is what it looks like with only the green:

Boats in Venice GIMP tutorial

And here is what it looks like with only the blue:

Boats in Venice GIMP tutorial

Step 5: By using the eye button to control what colors you want to be used in your black and white image, as well as using the opacity to control how much of each color will be used in the final image, you can create the best black and white rendition of your original photo.

Boats in Venice GIMP tutorial

Step 6: Save!

Boats in Venice GIMP tutorial
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