Monochrome on GIMP – using layers

Layers. Everyone knows that the good photo editing software suites have them, but nobody in the world has ever figured out what they’re for.

I’m exaggerating of course, but layers really are a bit of a dark art. I’ve been digging through my photography magazines and how-tos, and here’s a small tutorial on how to use layers to convert a photo to black and white. I’ll be using GIMP, a free and powerful image editing software. Photoshop is similar, just probably a bit better.

This is the photo I chose, a detail shot from the Monument to Discoveries, in Lisbon. Not bad, but not interesting either. However, the texture and shadow-light contrast made me think this would work in monochrome.

GIMP Mono 01

First, open the image on GIMP. Drag the windows and toolboxes around until you’re comfortable. This is how I like it:

GIMP Mono 02

Here’s a good way to perform the basic mono conversion. Click Colors -> Components -> Channel Mixer. Tick the monochrome box, and move the sliders of the three output channels, according to what color you want to filter for. In this case, I went for 100 Blue, 15 Green. Choose what looks better to you.

GIMP Mono 003The basic conversion lacks contrast. This is normal, converted images usually do look rather flat. At this point I would usually adjust curves, but there are problems with it, which I have documented before. Solution? Try out GIMP’s layers.

To add a layer, right click over the image -> Layer -> Duplicate Layer.

GIMP Mono 04At this point you have two identical images, one over the other; visually, nothing has changed. What we’re going to do now is change the type of light in the second image, the “top” layer. On the top of the “Brushes” palette (the movable toolbox to the right), locate the “Mode” drop list and select “Soft light”. Try other “modes” – you’ll learn something from seeing what happens.

GIMP Mono 005

And here is the result. Better, isn’t it?

GIMP Mono 06

However, I found the contrast way too harsh. Solution? Reduce the opacity on the horizontal slider under “mode”.

GIMP Mono 07I selected 61.5%, simply because it looked good to me. Here’s the result. Much better, I think: contrast and texture are just so to my eyes.

GIMP Mono 08It won’t win any contests anywhere, but it certainly looks better than the original. I like the result, and I enjoyed the process of creating it. Give it a go!

This entry was posted by Carlos Ferreira.

4 thoughts on “Monochrome on GIMP – using layers

  1. I don’t use GIMP but it is interesting to see how it works. With the picture it looks good as a black and white. Maybe some localized contrast adjustments but i would have no idea how you do it in GIMP.

      • I can see that happened. I have personally never tried Photoshop – I’ve been using GIMP for a few years now. The community seems to be constantly working on it, including on the interface.

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