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• In the documentation examples we often use <L.> in place of L. There's no functional difference.
• lpe:CD<L.> means camera with diffuse scattering event for light scattering type.
• lpe:CO means camera with emissive objection (since emissive does not need any light, there is no L).
• Using . in  in place of [DS] is shorthand, if you are using a User Lobe, you must specify U and cannot use the . shorthand
• lpe:CS*D*[LO] means all light paths minus caustic light paths. While caustic paths (defined here as diffuse followed by specular) may contribtue significantly to the final image, they are a common source of fireflies and flickering. 
• Similarly, lpe:CD+[LO] means all diffuse light paths minus caustics and lpe:CS+D*[LO] means all specular light paths minus caustics.