Question about lights

Say i need an LED lightbulb or a tubelight.

Now i make the mesh and materials etc.

Now should i use emission or add light sources?

do both work the same way? Which is more realistic?

Emission only provides “light” with Bloom on (in Eevee). It provides light regardless in Cycles. If you’re using Cycles, I would use emission. If you’re using Eevee, I would use light sources

So it works like IRL in Cycles?

Yes but also no. It acts like real light, but it doesn’t have Bloom like Eevee does, and it will double the amount of noise (increasing the number of samples you’ll need, probably.)

Emission works out of the box in Cycles. As long as you have a shader with emission either through the emission shader or the emission features from the principled BSDF node, the emission does not require any extra settings.

A couple of things to keep in mind though. If you use emission shaders together with lamps, the amount of noise in your image will double.

The second thing to keep in mind is that a ray-traced render engine such as Cycles does not have any bloom effect by default. This is a post processing effect. Normally we get bloom when taking a photo nd it is a pleasing effect even if it is a defect from the camera. Since a ray-traced engine does not simulate this effect we need to add it in post-production if we want it.

Once your image is rendered in Cycles, you can switch to the Compositing workspace and check ‘Use Nodes’ at the top. You will then be able to see the ‘Render Layers’ and ‘Composite’ nodes. Use Shift+A to add a node called ‘Glare’ and place it in between the 2 current nodes.

Setting the Glare node to ‘Fog Glow’ is often the best choice to achieve the bloom appearance, but you can experiment with the different options and settings to see which best achieves the look you are going for.


Something else to ponder: "a lightbulb or a tubelight is a so-called “practical light.” It’s something visible in the frame which “you know” is “a source of light.” So, when you see that this thing is “lit,” and then when you see that it appears to be “lighting-up something nearby,” it might not initially occur to you that these two effects might be most-easily handled as separate concerns.

In the theater, the actor switches on a lamp. “The lighting changes subtly.” But, the actual “source of light” that actually did it is high overhead.