Hi here my method to render and setup a moonlight scene.
to get the right moonlight intensity,first we have to know ,how much of the sunlight, is the moon reflecting.
i found the IOR of the average moon surface in the net ,its 1.78 ±0.03.
a reflection at F0 would be around 8% from the sunlight.
F0=( (1-1.78)/(1+1.78))²
F0 in this case is around 0.079
to get the intensity with a HDRI,first we have to set the colormanagment to Filmic,and give a object in the scene a diffuse mat with a value of 0.18 grey.now we can set the Filmic to Falsecolor and adjusting the light strength of the HDRI to the point there it hits the keylight to grey and switch then back to Filmic.
know we can multiply this strength value with our F0 value to get the moon intensity.
another method would be to just to reduce the exposure to around -3 stops.(but is not used here)
next we need to know the colortemperature from a nightsky.I found a value in the net of 34500
now we can multiply our HDRI with a blackbody node to get the tint of 34500 temp.
I looked at around 8 cinema movie scenes to see how they setup the light at skintones.and made a final grading with the compositing nodes,and multiplyed the renderresult with a color of 0.33 ,1 , 1 to reduce the red even more
thats it.happy blending
It’s kind of a weird thing. If you photograph the moon, you’ll find that it has the same color temperature as the sun - makes sense, reflecting it I guess. The purkinje shift towards blue is a human vision experience as we become more and more color blind the darker it gets, loosing the blue cone sensitivity last. At sunlight you have bright red flowers against a darker green, while at sunset the green appears brighter than the now very dark red (also quite desaturated). If dark enough, we’re either seeing in greyscale or a hint of blue if the blue cones are stimulated enough. But 34500 or 12000 doesn’t seem to make a difference for me, maybe it’s just better to multiply with a blue’ish color?
However. Areas in an image that still produce enough light to stimulate the cones, will appear to have normal color. So I tend to agree to color the environment towards blue (keeping other sources as is) instead of doing it all in grading. Example.
Sidenote: If the example above is a blue-for-night shot, the handheld candle light would not be bright enough to outshine the environment like that, and is mostly motivating an off screen bright warm light.
Unless you’re going for an extremely cold and heartless feeling, I would suggest adding points of warmth to the image. Like this witcher intro screen image where you can also see the warm light from an off screen fireplace reflect off Geralt to balance out all that blue. Grading this as blue-for-night (without masking) would just look off. Fog/haze is also a way to separate foreground from background/add depth. Sorry for incoherent reply, trying to do too many things at once
like i sayed,i found the average colortemperature from different nightsky intensitys in the net (34500k).stars can have colortemps above 30000+k .i just tryed out to tint its this way,and to me it gives a more blueish look.
All what you sayed is a matter of taste (eg Witcher)btw the Wicher scene has more lightsources than the nightsky and the moonlight,this wasnt the goal here.
I showed just a simple way to make a nightsky/moonlight look with just one HDRI as lightsource.
the additional red reduction in the compositing node,its a artistic choice based on some colorpicking cinematic scences,what i want to imitate to some degree,since we are making nothing else.
here are the video scenes i have used for reference ,as you can see and the speaker says,the blueish greenish silver desaturated looks,all is a matter of mood and taste.
edit,you can use in therory all hdris to simulate a night scene.like i sayed its used in the film industry many years before.eg some film scences was shooting at midday time and they just used blue gel filters over the camera,or reduced the exposure.and like you see in the video the lighting styles and intensitys variation is huge.
the colorgrading if done more professional,is done with skintone masking ect.you can try it to some degree for you self,the only limitation with the hdris are,they can have a strong overall tint,like sunrise or dawn,and the dynamic range isnit fit very well,what you can hardly grading.
