Use Linear Color Space. It’s important to choose a ‘Color Space’ before lighting your project. The preferred Color Space for realistic rendering is Linear. By default Unity use Gamma Color Space. To change it go to (Edit > Project Settings > Player), inside Other Settings tab you will find Color Space* – change it to Linear. Read more about Gamma and Linear Color Space HERE.
Use Global Illumination (GI) – for more realistic lighting. It’s a system that models how light is bounced off of surfaces onto other surfaces (indirect light) rather than being limited to just the light that hits a surface directly from a light source (direct light). Read more about Global Illumination.
To turn on Realtime Global Illumination go to (Window > Lighting > Settings), Lighting window will appear. Open Scene tab inside Lighting window and enable Realtime Global Illumination. You can change Realtime GI resolution by changing Indirect Resolution.
Both Baked GI and Precomputed Realtime GI have the limitation that only Static objects can be included in the bake/precomputation – so moving objects cannot bounce light onto other objects and vice versa. However they can still pick up bounce light from static objects using Light Probes.
Color Harmony. You must understand colors to create nice lighting and atmosphere in the scene. Read more about Color Harmonies.
Different lighting colors can change the scene mood drastically:
Use very Light Colors, Don’t use Over Saturated colors! Light colors are much more pleasant to the eye, and looks more realistic. Watch this video to Understand Colors more – by Andrew Price.
Play with Lights – change Light Direction and Shadows to get different results.
Play with Ambient Color to change shadows color. You can get pretty nice results by changing shadows color.
You can do it by going to (Window > Lighting > Settings), Lighting window will appear. Inside Lighting window open Scene tab and set Environment Lighting Source to Color. Now you can change Ambient Color to any color you want.
Use Post-Processing image effects. By using Post-Processing image effects you can improve overall scene lighting very drastically. Here is an example in Unity 5.6 – I’ve used FREE Post Processing Stack from Unity Asset Store.
I hope that these few tips will help you to improve your overal lighting in Unity. Keep learning and practice every day! 😉
If you have any questions, feel free to ask!