I’m trying to create an instructional video about one of our boards and wanted to show the name (and later on the diagnostic patterns) of the LEDs on the board. I have three colours, red, green, blue, and despite the materials have an overall similar structure (except for the colour), the result of the emission and the compositing is completely different one from the other.

Where am I lost? What am I doing wrong? These are the images of the LEDs:


Green LED Blue LED

The most satisfactory one is the green, and the least satisfactory the blue which seems to have no bloom whatsoever. The three LEDs have a different model but the issue does not depend on the model, as I have applied the blue material to the green LED without ay improvement.

Here are the Nodes I used in the shader: Green Shader setup

And the compositor nodes: enter image description here

The super odd thing (to my eyes, at least) is that I had to use a threshold of 2 as despite the blue material has a much higher emission value in comparison to the green and red (50 vs 15), the glare effect disappears if I set the threshold higher than 4.9 (say, 5).

Thanks to everyone who can help me shed some light on this doubt.

Edit: just to clarify, this it the real appearance of the device:

enter image description here

so practically, the opposite of my render. However, I'm not after photorealism but at least I'd like to have a more evident glow around the blue lights. I'm open to any solution (compositing, render layers, etc.)

  • $\begingroup$ can u provide blend file? $\endgroup$
    – Chris
    Nov 11, 2021 at 11:47
  • $\begingroup$ I can't find it at the moment, but there once was a question here where someone else also was wondering why his glowing colored lights looked different. In short, I explained that for example a white light where you have RGB (1/1/1) is of course brighter than a completely red light with RGB (1/0/0) since the green and blue channels are not emitting any light. Another thing is that different colors are perceived with different brightness for the eyes or even optical instruments, I don't know how much this is relevant in the render engine though. $\endgroup$ Nov 11, 2021 at 12:04
  • $\begingroup$ using Eevee, you can use bloom instead of the compositor. $\endgroup$
    – lemon
    Nov 11, 2021 at 12:06
  • $\begingroup$ @OmarFilippini What is your Base Color ... from your screen it doesn't look like the same ... green is green, but Red and Blue are what? If I set it appears as brighter color when black its intensive color, but never black (or. dark grey) like in your screen. $\endgroup$
    – vklidu
    Nov 11, 2021 at 13:04
  • $\begingroup$ @gordon, actually being that (just by chance) the colours of the LEDs are R, G and B, for each led there's one of those colours having the emission close to 1 $\endgroup$ Nov 11, 2021 at 14:26

1 Answer 1


I'm not sure if there is too much to say ... blue is just visually darker color ... so less prominent for blooming. Here all colors intensity of 10.

enter image description here

Options for compensations are several ... it depends on circumstances ... here just Emission Strength Red 20 / Green 10 / Blue 40 + brighter blue color R0/G0.2/B1

enter image description here

Notes: Base color is set white here. Used default Bloom setup (Render Properties).

Also helps to use not strongest color like Red 1/0/0 but brighter 1/0.1/0.1. Here with few adjustments in Color Management > Filmic > Very High Contrast, Exposure 1.8, Gamma 0.3 ... but can be enhanced also in compositor.

enter image description here

Result of Compositor > Glare > Fog Glow is the same ... there you can duplicate this node few times to even make the effect stronger ... and the same can be achieved by Bloom > Intensity and Radius too.

Speaking to Treshold - it is based on color intensity ... so it make a sense if bloom is cropped in order blue-red-green.

enter image description here enter image description here

Your file can be fixed in the same way provided in this answer ... just keep in mind - you can't see a light without darkness :)

enter image description here

This is what I meant by simplified file share via https://blend-exchange.com

Related - RGB to BW

  • 1
    $\begingroup$ @Chris thank you for your comment. The blend file can be discharged here: drive.google.com/file/d/1rpaBf4aI2COY1i9fuu6_3U4xUFykutb6/… $\endgroup$ Nov 11, 2021 at 14:00
  • 1
    $\begingroup$ thank you. I'm not using the bloom effect as it gave me a bloom effect (sort of an halo) also around other component, but I now found out that the problem was due to the threshold set at 0.8. However, there's no improvement in using bloom vs the compositor $\endgroup$ Nov 11, 2021 at 14:21
  • 1
    $\begingroup$ Yes ... that is right - Bloom in Eevee is the same as your Glare>Fog Glow in compositor ... and I'm not saying you to use it .. it was just a note what I used ... I guess Lemon suggested to you, because it is just more straight forward solution to see result realtime in 3D view. I tried to explain why it is less blooming and what should help. $\endgroup$
    – vklidu
    Nov 11, 2021 at 14:29
  • 1
    $\begingroup$ Thanks for the file ... just to let you know - the proper way is to use blend-exchange.comm to upload file and copy-paste given code into your question via edit. Also like now people has to ask you for access and be owner of google account Thank you keeping site organised. $\endgroup$
    – vklidu
    Nov 11, 2021 at 14:31
  • $\begingroup$ Thanks @vklidu, your suggestions proved to be very useful! $\endgroup$ Nov 24, 2021 at 15:40

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