How To Do An Infrared Channel Swap in Affinity Photo

How To Do An Infrared Channel Swap in Affinity Photo

In this article, I will explain how to make a channel swap, for an infrared photo using, Affinity Photo. If you have already read my article explaining how to channel swap in Photoshop, you will already know why we might want to do this.

Unlike the popular myth suggests, channel swapping isn’t an essential part of infrared photography. Whilst it can help with black and white infrared post processing, it isn’t essential. The only time that you really need to perform a channel swap is when areas of colour in an infrared photo don’t match what you require.

A typical example where we might channel swap is a colour infrared photo like this.

Here you can see the sky and grass have a yellow/red tint whilst the tree has a slight blue tint. These colours are the result of the Custom White Balance applied to the RAW file in camera when it was captured.

The Importance of White Balance

If you read the Photoshop channel swap article, you will know that I mention the importance of white balance at the beginning. That’s because it’s important, and many RAW processors like Adobe Lightroom can’t handle the White Balance set in the camera. This then causes the RAW file to appear red.

With the image above, you are seeing the White Balance set in the RAW file by the camera. This is also what you will see when you open the RAW file in Affinity Photo’s Develop Persona. Whilst it can be tempting to tweak the White Balance setting in the Develop Persona, please don’t. Trying to do so (at the time of writing) causes the colours to change dramatically and you can’t recover the position with using the Undo command in the Edit menu.

You can however apply other adjustments like sharpening and tonal/contrast adjustments, without affecting the White Balance. When you are ready, click the Develop button to process the RAW file and switch to Affinity Photo’s Photo Persona.

If you are using Affinity Photo 2, you can also choose to produce an Embedded RAW layer rather than a Pixel layer. This has the benefit of allowing you to reopen and continue adjusting the RAW files settings. It’s a technique I demonstrate and explain in this article about Double RAW processing.

Adding a Channel Mixer Layer

When the image is open in the Photo Persona, add a new Channel Mixer Adjustment Layer. You can do this by clicking the Adjustment icon at the bottom of the Layers Studio Panel, indicated below.

When you click the Adjustments icon, it displays a list of available Adjustment Layers. Scroll down the list to find “Channel Mixer” and select that. You will then see the new Channel Mixer Adjustment added at the top of the Layers Studio Panel.

Having added the Channel Mixer Adjustment, you will see its dialog displayed as shown below.

At the top of the dialog, you can see the Output Channel with two dropdown lists. The first list on the left allows us to choose the format of the image to adjust. For an infrared photo, this should be set to RGB. The second dropdown allows us to choose the colour channel we want to swap.

A typical channel swap involves swapping the colours of the Red and Blue colour channels, but you can also swap other colour channels. Which is best depends on the colours produced in the image by your White Balance. We will look at a Red/Blue channel swap because that’s one of the most popular.

Making a Red/Blue Channel Swap

Start by selecting the Red colour channel in the dropdown list. You should see the Red slider is set to 100% and the other sliders to 0%.

Click and drag the Red slider left to a value of 0%. You can also click on the number (100%) in the field and then enter 0. As you do this, you will see the colours in the image change.

Now click the Blue slider and drag that to a value of 100%. Again, you can enter the values in the number fields if you find this easier.

We now need to change the dropdown at the top of the dialog to Blue so that we are editing the Blue colour channel. When you do this, you will see that the Blue slider is at 100% and the other sliders at 0%.

Move the Red slider to 100% and the Blue slider to 0% to complete the channel swap. You can see the Channel Mixer adjustments in the following screenshot together with the image.

White Balance Options

In this example, the sky in the image has a strong blue cast which is also affecting the tree. Part of this problem lies with the initial colour balance set in the camera.

If you decide that you don’t want this and would like to adjust the colours, add a White Balance Adjustment layer to the image. You can do this in the Layers Studio Panel by clicking the Adjustment icon at the bottom. Then when the White Balance dialog appears, use the sliders to control the colour as shown below.

If you would like to learn more about digital infrared photography, read my article explaining what you need to know.

More Affinity Photo Tutorials

You’ll find more high quality, free tutorials on my Affinity Photo Tutorials page.