Overhead of using SceneColor?

In translucent materials, is using SceneColor adding any overhead? Translucency is rendered over the top of opaque so isn’t it performing this operation anyway? Also, by using SceneColor I can bypass Opacity all together - is that the idea or is there something silly about using SceneColor over opacity?

Scene color is copy of the render target. So there is fixed price overhead per material that use Scene color:

I’ve used Scene Color myself to bypass the issue of shorelines fading out the specularity with depth fade (which is not desirable for water surfaces). Scene color is akin to using the pixel normal: you’re just taking a copy from the G-buffer. This is actually what you should do if you want to change the water’s color but not the opacity of the whole material.