"Deferred lighting" flag in SceneCapture2D settings: what's happening when it's unchecked?


I’m working on shaders using a scenecapture2D actor and noticed a boost in fps when I uncheck “Deferred Lighting” in the advanced show flags of the scenecapture settings.
I’ like to know what is exactly happenning when it’s unchecked: does the engine uses forward lighting? And why does it boost fps?
Also I noticed that metallic materials were incorrectly lightened when unchecked: why?
I found nothing about it in the unreal doc.


I think I figured it out: when deferred lighting is unchecked, the scenecapture displays the diffuse color of the meshes, like when using “scenetexture: diffuse color” in a postprocess material.
So, when unchecked, you don’t switch to forward lighting but you have no lighting as with unlit materials.
Explains better performance.