Low Light Render

OminousAutumn

Hi all. How do people create renders in low light without so much grain? The below render isnt even that dim and yet the fill light area is covered in grain. How does one get nice clean and clear skin?!?!?! I am using ghost lights and the environment bc that seems to render the fastest and provide nice highlights, iray, 15,000 samples, no time limit, %97 convergence ratio, and the pixels are at like 2000 x 1200. Render still takes an age, but I dont mind long renders if they yield result. All thoughst welcome, thanks!

evilded777

Define "no time limit".

rames44

One approach to making a scene seem dim without freaking out iRay is to set the scene up with a “normal” amount of light and then darken it by using the settings in the Tone Mapping panel under Render Settings. Essentially, you can reduce the exposure, darkening the final result, while still leaving enough light in the scene to make iRay happy. 

Also, the “denoiser” in the 4.11 beta might help...

JonnyRay

SickleYield has a video on techniques for doing night renders which may help.

Tobor

The old Hollywood trick for "day-for-night" shooting was to increase the f/stop on the camera a certain amount, but also "push process" the film by at least one stop to increase contrast (that involved leaving it in the developer for longer). They also introduced a blue filter (for color), plus maybe also decolorize a bit because at night our color acuity is reduced. (Just think of the old Moody Blues poem/lyric: "Cold-hearted orb that rules the night, removes the color from out sight. Red is gray and yellow white...")

We don't need to develop film, but the Tone Mapping controls also include options for altering the tonal balance by way of the crush, burn, saturation, and other sliders. You can pretty much accomplish everything with Tone Mapping that a quarter-million dollar aerial printer did old movies (and those are 1960's dollars!) 

All this said, simply boosting all the lights in the scene isn't going to do squat for render times. It's not the amount of light (after a certain minimum amount(, but the coverage of the light. Iray takes the longest when the light is indirect, which pretty much looks like what's going on in the OP's sample. Direct lighting is direct rays from a quality HDRI, one of the built-in light lamps (spotlight, point) etc. or a very nearby emissive source. Indirect is all the light in the scene that must first bounce around before it fills in the shadow areas.

dracorn

Mesh lighting products can also help.  I like to use Ghost Lights 2, Rim Light Rig Iray, and even spotlights or linear point lights.  

https://www.daz3d.com/iray-ghost-light-kit-2

https://www.daz3d.com/rim-light-rig-iray