In this short video tutorial, I’ll show you the Compositing node group I created to recreate a simple Halation effect in Blender.
Video Transcript
Hello everyone! In this short video tutorial, I’ll show you the Compositing node group I created to recreate a simple Halation effect in Blender. The tutorial was made using Blender version 4.3, but the nodes used have been available for several versions and will likely remain available in the future.
First of all, let’s define the Halation effect. It’s an effect that appears as a reddish or orange glow around very bright areas of an image, especially in spots with overexposed light.
It’s a typical effect of color film photography, which is why it’s sometimes intentionally added in post-production to recreate the look of film, especially in projects aiming for a vintage or cinematic aesthetic. So if you want to mimic the look of film, Halation is one of the effects to consider, along with Glare, Lens Distortion, Film Grain, and others.
To implement this effect in Blender, we first need to isolate the brightest areas of the image. This can be done using a Math node set to Greater Than with a high value for the second input, basically using this node as a threshold to make all parts of the image darker than a certain value turn black, and all the brighter parts turn white.
This node should be used on the image converted to grayscale using an RGB to BW node. The grayscale image should also be processed with a Normalize node, since the values in rendered images are generally not within the 0 to 1 range, and the Greater Than node might give incorrect results without normalization.
I connected the second input of the Greater Than node to one of the inputs of the node group, so the threshold value can be adjusted from outside the group. I’ll show some practical examples later on.
We now have an image where the bright areas are white, and everything else is black. We want to create a reddish glow around the white parts, but we don’t want the white center itself. To do that, we first blur the mask using a Blur node set to Fast Gaussian. I connected the Size parameter of this node to one of the group inputs, so it can be easily adjusted later, just like the second input of the Greater Than node.
To give this glow a reddish tint, I multiply the output of the Blur node using a Color Mix node set to Multiply, and I set the second color of the node to red.
Finally, I subtract the unblurred white mask, coming from the Greater Than node, from the reddish glow, so that only the outer halo remains. This operation is done using a Color Mix node set to Subtract. It’s important to enable the Clamp option here to prevent the subtraction from producing negative values, as those could cause unwanted artifacts in the final result.
The result from the Subtract node can then be added to the original image using a Color Mix node set to Add. As you can see, I connected the Factor input of this node to one of the group’s inputs, so it can be adjusted externally.
I also connected the output of the Subtract node to another output of the group, labeled FX Only, so the effect alone can be previewed more easily when tweaking its parameters. This operation is done outside the group, so now I’ll close it and show you a few examples.
By connecting the FX Only output to the Viewer and Composite nodes, I can preview only the effect that will be applied to the original image. On the other hand, by connecting the Image output of the Halation group to those two nodes, I get the final image with the effect applied.
The Add Factor, Blur Size, and Threshold parameters we’ve discussed earlier allow us to control, respectively, the intensity of the effect applied to the original image, the width of the blur, and the brightness threshold beyond which the effect is triggered.
The Add Factor parameter is therefore not useful when using the FX Only output, because it’s only used when the effect is added to the original image, so its impact is visible only when using the Image output of the node group.
The FX Only output, on the other hand, is extremely helpful for adjusting the Blur Size and Threshold parameters, allowing you to clearly see which areas the effect is being applied to and how wide the red halo is.
Once those parameters are set, you can use the Image output of the node group and then tweak the Add Factor value according to your needs.
Unlike most of my video tutorials, a PDF version of this tutorial is not currently available for download. However, you’ll find a link in the description to the page containing PDF versions of many of my other tutorials. In any case, now’s a great time to subscribe to the channel and turn on notifications!
Alright, I hope you found this short tutorial helpful! See you soon!