@SdvL - in the good old days, low light required fast film or long exposure time. Fast films (eg ISO 1000) were grainy - and had to be kept in the fridge.
In Lux (and Octane) low light means grainy results OR longer render time, the graininess reduces while the clock ticks on.
Octane on GTX760 can handle 144 color texturemaps plus 68 grayscale maps. If these were all 4000x4000 they would require about 10Gb anyway, which won't fit into any videocard. Usually one needs to rebuild materials anyway for decent results.

@KJHerstin - Reality like any other tool is quite limited in translating the Poser material tree. From what I see I'm not sure the translation is going very well I all cases. Essentially one has to rebuild most materials to get real decent results, unless the Poser mats are pretty simple (the main color swatches and images maps, nothing else).
Quoting from my Poser to Lux tutorial in the making:

So, which Poser material properties can get transferred?
• Diffuse_Color, Alternate_Diffuse, and any image maps and even some other nodes attached. But Diffuse_Value and anything attached is not dealt with.
• Image maps attached to Specular, but all other elements are not dealt with.
• Ambient is not dealt with.
• Image maps attached to Transparency end up in Alpha, but all other elements are not dealt with.
• Translucency, Reflection and Refraction are not dealt with.
• Bump and Displacement values and image maps attached end up in Modifiers.
That’s about it.

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Usually I'm wrong. But to be effective and efficient, I don't need to be correct or accurate.

visit www.aRtBeeWeb.nl (works) or Missing Manuals (tutorials & reviews) - both need an update though