TUTORIAL -- Shooting Day for Night

CrissieB

It's difficult to render very-low-light scenes with Iray in DAZ Studio. Images tend to be grainy unless you double or treble the image size, increase the Convergence from 95% to 99%, and increase your Max Iterations and Max Render Time so your GPU can grind away for hours. And even then, you may get a grainy image.

All of that is because DAZ's Iray render engine works very much like a real camera, driven by the real physics of light. So it's difficult to render very low-light-scenes for the same reason it's difficult to shoot movies or photos in very low light: the camera just isn't as sensitive as the human eye.

But there's a surprisingly easy solution that uses the same techniques cinematographers began developing in the 1930s. It's called "Shooting Day for Night" and, unlike most real cameras, you can render a nighttime image from a daytime scene with little or no post-processing. And it's fast.

Let's start with a simple scene, a kiss in the park. Here it is, rendered with default daylight settings:

The background is this free HDRI, with the Render Settings>Environment>Environment Intensity reset from 1 to 0.25 and the Environment Map reset from 2 to 1. Those two changes pulled a very bright, sunny day down to an overcast day, which you need when shooting Day for Night.

I put the sun behind the characters, because I want the final image to show them partly silhouetted by moonlight. The front lights are two primitive spheres, each 1m in diameter, set to Iray Emissives with Emission Temperatures of 2900K and Luminosities of 1.5 million lumens. The image looks slightly golden because the default render settings assume normal daylight (Emission Temperature 6500K) but the front lights are simulating incandescent streetlights.

At 1000x1300 pixels, the daytime image rendered in 4 minutes 35 seconds with my NVIDIA GTX 980 graphics card. That was my benchmark.

Next I made these changes to my Render Settings>Tone Mapping:

To shoot Day for Night, you need to change a few things:

(1) Underexpose the image. I halved the Shutter Speed from 1/128 to 1/256 and pushed the Render Settings F-Stop (which works like the F-Stop on a camera) up from the default 8 to 24. That will make the image much, much darker.

(2) Adjust the White Point. The human eye is more sensitive to shorter frequencies in very low light, so moonlit objects seem slightly blue (the Purkinje Effect). That effect is greater if objects are front-lit by lower-temperature lights, because the eye and brain combine to 'see white' in varying light conditions. So I changed the White Point from default 6500K white (1.0-1.0-1.0) to the golden tone of the 2900K streetlights (1.0-0.8-0.4). The render engine will resolve that color as white and resolve whiter colors as bluish ... exactly what we want when shooting Day for Night.

(3) Adjust the Highlights and Shadows. Highlights pop more in low light, while shadows are more muted. So I reset Burn Highlights from the default 0.25 up to 0.40, and reset Crush Blacks from the default 0.20 down to 0.10.

(4) Reduce the Color Saturation. Our eyes are less color-sensitive in low light, so I lowered the Saturation from the default 1.00 to 0.90.

Note: I made these adjustments with my Viewport set to Iray mode, so I could see the effects in real time. For example, the woman on the right is wearing a blouse with white stripes, so I adjusted the White Point until those stripes looked white in my Viewport. If you don't have a graphics card, you can fine-tune with half- or quarter-sized test renders. You don't need fine details in those test renders; you just need to see how your changes affect the lighting and color balance.

Tip: If you do have a graphics card and can adjust in Iray mode then, once you're happy with the image, reset the Viewport to Texture Shaded, save, close DAZ Studio, and reload the scene. That will clear your GPU cache, so it won't get hung up and dump the render to your CPU.

Now you're ready to render your Day for Night image:

​

Note that this is exactly the same scene as the one at the top. I did not change the HDRI or the lighting. All I did was adjust the Tone Mapping to shoot Day for Night ... and the daytime park becomes a nighttime park, the characters partly silhouetted but still visible in detail, complete with bluish highlights from the moonlight.

The really cool part: I rendered that at twice the resolution (2000x2600) and to 99% rather than 95% convergence -- to pack in more detail -- and it still rendered in only 3 minutes 25 seconds. That's over a minute faster than the original, and hours less than if I'd reset the lighting to be that dark at typical render settings. My only postwork was to resize the image to match the original 1000x1300.

If you've wanted to render dark, moody, nighttime scenes but balked at huge render times and grainy images ... try the trick that movie directors have used for decades: shoot Day for Night!

RobotHeadArt

Cool tutorial!  Thanks for explaining the why and not just the what.

frankrblow

+1

Clear and simple to understand. Thanks, CrissieB

CrissieB

Thank you, and you’re welcome, RobotHeadArt and dragonfly_2004!

Here’s another version of the same scene, this time with the Skies of iRadiance NightTimeA HDRI, the CityScapes CS08 Curved Large backdrop, and a homemade moon:

The front lighting and Tone Mapping settings are the same as before.

The moon is a primitive sphere, 20m behind the scene. It has this free texture in the Base Color and Emission Color channels. Its Emission Color is 1-1-1 white, with an Emission Temperature of 4100K (the color temperature of moonlight) and a Luminosity of 20 million lumens.

To increase the ambient moonlight, I boosted the Render Settings>Environment>Environment Intensity from 1.0 to 2.0.

To color-balance the city lights, I reduced their Emission Temperature to 2400K.

With the lighting I used, this scene would be ridiculously bright at the default render settings. If I adjusted the lighting to be this dim at the default render settings, it would take ridiculously long to render ... and the image might still be grainy.

But by Tone Mapping to shoot Day for Night, I rendered this at 2000x2600 pixels and 99% convergence in just 5 minutes, 45 seconds. And again, my only postwork was to reduce the image size to 1000x1300.

srinity

Just wanted to say thanks for this!  

CrissieB

You're very welcome, srinity! :-)

Galamesh

I wanted to thank you too!. Terrific tutorial. It helped me so so much.

Cheers!

mwasielewski1990

Wow, absolutely genius. I'd never think of using tone mapping for this  How about indoor scenes, will this work the same way?

Galamesh

mwasielewski1990 said:

Wow, absolutely genius. I'd never think of using tone mapping for this  How about indoor scenes, will this work the same way?

I'm using the technique indoors. It works perfectly. I set a moonlighting comming from the window with a very high ammount of lumens.

 

 

the_powerz

This is some straight up brilliance. I was having a hell of a time trying to coax IRAY into making a night scene.

As I am relatively dumb I was losing. Now I am powered by your know how I can finally succeed, and maybe get some real sun.

Ah no what am I thinking. I'll just set up an HDRI and bask in the glow of my success.

Thanks for this.

+1

CrissieB

Thank you, the_powerz! 

mikethe3dguy

Glad I found this when I did, and THANK YOU for the detailed tutorial! I've just been struggling with a night scene, and I'm going to try this.

Catherine3678ab

My thanks as well :-)

 

CrissieB

You're welcome, Mike and Catherine! Enjoy!

rziganshin12

I just found it and it is great!!!! Thank you!!

Tarantanamir

Wow, thanks, this comes in handy.

Dazzle_4578436

CrissieB said:

It's difficult to render very-low-light scenes with Iray in DAZ Studio. Images tend to be grainy unless you double or treble the image size, increase the Convergence from 95% to 99%, and increase your Max Iterations and Max Render Time so your GPU can grind away for hours. And even then, you may get a grainy image.

All of that is because DAZ's Iray render engine works very much like a real camera, driven by the real physics of light. So it's difficult to render very low-light-scenes for the same reason it's difficult to shoot movies or photos in very low light: the camera just isn't as sensitive as the human eye.

But there's a surprisingly easy solution that uses the same techniques cinematographers began developing in the 1930s. It's called "Shooting Day for Night" and, unlike most real cameras, you can render a nighttime image from a daytime scene with little or no post-processing. And it's fast.

Let's start with a simple scene, a kiss in the park. Here it is, rendered with default daylight settings:

The background is this free HDRI, with the Render Settings>Environment>Environment Intensity reset from 1 to 0.25 and the Environment Map reset from 2 to 1. Those two changes pulled a very bright, sunny day down to an overcast day, which you need when shooting Day for Night.

I put the sun behind the characters, because I want the final image to show them partly silhouetted by moonlight. The front lights are two primitive spheres, each 1m in diameter, set to Iray Emissives with Emission Temperatures of 2900K and Luminosities of 1.5 million lumens. The image looks slightly golden because the default render settings assume normal daylight (Emission Temperature 6500K) but the front lights are simulating incandescent streetlights.

At 1000x1300 pixels, the daytime image rendered in 4 minutes 35 seconds with my NVIDIA GTX 980 graphics card. That was my benchmark.

Next I made these changes to my Render Settings>Tone Mapping:

To shoot Day for Night, you need to change a few things:

(1) Underexpose the image. I halved the Shutter Speed from 1/128 to 1/256 and pushed the Render Settings F-Stop (which works like the F-Stop on a camera) up from the default 8 to 24. That will make the image much, much darker.

(2) Adjust the White Point. The human eye is more sensitive to shorter frequencies in very low light, so moonlit objects seem slightly blue (the Purkinje Effect). That effect is greater if objects are front-lit by lower-temperature lights, because the eye and brain combine to 'see white' in varying light conditions. So I changed the White Point from default 6500K white (1.0-1.0-1.0) to the golden tone of the 2900K streetlights (1.0-0.8-0.4). The render engine will resolve that color as white and resolve whiter colors as bluish ... exactly what we want when shooting Day for Night.

(3) Adjust the Highlights and Shadows. Highlights pop more in low light, while shadows are more muted. So I reset Burn Highlights from the default 0.25 up to 0.40, and reset Crush Blacks from the default 0.20 down to 0.10.

(4) Reduce the Color Saturation. Our eyes are less color-sensitive in low light, so I lowered the Saturation from the default 1.00 to 0.90.

Note: I made these adjustments with my Viewport set to Iray mode, so I could see the effects in real time. For example, the woman on the right is wearing a blouse with white stripes, so I adjusted the White Point until those stripes looked white in my Viewport. If you don't have a graphics card, you can fine-tune with half- or quarter-sized test renders. You don't need fine details in those test renders; you just need to see how your changes affect the lighting and color balance.

Tip: If you do have a graphics card and can adjust in Iray mode then, once you're happy with the image, reset the Viewport to Texture Shaded, save, close DAZ Studio, and reload the scene. That will clear your GPU cache, so it won't get hung up and dump the render to your CPU.

Now you're ready to render your Day for Night image:

​

Note that this is exactly the same scene as the one at the top. I did not change the HDRI or the lighting. All I did was adjust the Tone Mapping to shoot Day for Night ... and the daytime park becomes a nighttime park, the characters partly silhouetted but still visible in detail, complete with bluish highlights from the moonlight.

The really cool part: I rendered that at twice the resolution (2000x2600) and to 99% rather than 95% convergence -- to pack in more detail -- and it still rendered in only 3 minutes 25 seconds. That's over a minute faster than the original, and hours less than if I'd reset the lighting to be that dark at typical render settings. My only postwork was to resize the image to match the original 1000x1300.

If you've wanted to render dark, moody, nighttime scenes but balked at huge render times and grainy images ... try the trick that movie directors have used for decades: shoot Day for Night!

Finding this years later withou the original Tone Mapping image setting feels like i missed out on some genius.
but ill try to put it together from the text and see what i can come up with.

Dazzle_4578436

CrissieB said:

It's difficult to render very-low-light scenes with Iray in DAZ Studio. Images tend to be grainy unless you double or treble the image size, increase the Convergence from 95% to 99%, and increase your Max Iterations and Max Render Time so your GPU can grind away for hours. And even then, you may get a grainy image.

All of that is because DAZ's Iray render engine works very much like a real camera, driven by the real physics of light. So it's difficult to render very low-light-scenes for the same reason it's difficult to shoot movies or photos in very low light: the camera just isn't as sensitive as the human eye.

But there's a surprisingly easy solution that uses the same techniques cinematographers began developing in the 1930s. It's called "Shooting Day for Night" and, unlike most real cameras, you can render a nighttime image from a daytime scene with little or no post-processing. And it's fast.

Let's start with a simple scene, a kiss in the park. Here it is, rendered with default daylight settings:

The background is this free HDRI, with the Render Settings>Environment>Environment Intensity reset from 1 to 0.25 and the Environment Map reset from 2 to 1. Those two changes pulled a very bright, sunny day down to an overcast day, which you need when shooting Day for Night.

I put the sun behind the characters, because I want the final image to show them partly silhouetted by moonlight. The front lights are two primitive spheres, each 1m in diameter, set to Iray Emissives with Emission Temperatures of 2900K and Luminosities of 1.5 million lumens. The image looks slightly golden because the default render settings assume normal daylight (Emission Temperature 6500K) but the front lights are simulating incandescent streetlights.

At 1000x1300 pixels, the daytime image rendered in 4 minutes 35 seconds with my NVIDIA GTX 980 graphics card. That was my benchmark.

Next I made these changes to my Render Settings>Tone Mapping:

To shoot Day for Night, you need to change a few things:

(1) Underexpose the image. I halved the Shutter Speed from 1/128 to 1/256 and pushed the Render Settings F-Stop (which works like the F-Stop on a camera) up from the default 8 to 24. That will make the image much, much darker.

(2) Adjust the White Point. The human eye is more sensitive to shorter frequencies in very low light, so moonlit objects seem slightly blue (the Purkinje Effect). That effect is greater if objects are front-lit by lower-temperature lights, because the eye and brain combine to 'see white' in varying light conditions. So I changed the White Point from default 6500K white (1.0-1.0-1.0) to the golden tone of the 2900K streetlights (1.0-0.8-0.4). The render engine will resolve that color as white and resolve whiter colors as bluish ... exactly what we want when shooting Day for Night.

(3) Adjust the Highlights and Shadows. Highlights pop more in low light, while shadows are more muted. So I reset Burn Highlights from the default 0.25 up to 0.40, and reset Crush Blacks from the default 0.20 down to 0.10.

(4) Reduce the Color Saturation. Our eyes are less color-sensitive in low light, so I lowered the Saturation from the default 1.00 to 0.90.

Note: I made these adjustments with my Viewport set to Iray mode, so I could see the effects in real time. For example, the woman on the right is wearing a blouse with white stripes, so I adjusted the White Point until those stripes looked white in my Viewport. If you don't have a graphics card, you can fine-tune with half- or quarter-sized test renders. You don't need fine details in those test renders; you just need to see how your changes affect the lighting and color balance.

Tip: If you do have a graphics card and can adjust in Iray mode then, once you're happy with the image, reset the Viewport to Texture Shaded, save, close DAZ Studio, and reload the scene. That will clear your GPU cache, so it won't get hung up and dump the render to your CPU.

Now you're ready to render your Day for Night image:

​

Note that this is exactly the same scene as the one at the top. I did not change the HDRI or the lighting. All I did was adjust the Tone Mapping to shoot Day for Night ... and the daytime park becomes a nighttime park, the characters partly silhouetted but still visible in detail, complete with bluish highlights from the moonlight.

The really cool part: I rendered that at twice the resolution (2000x2600) and to 99% rather than 95% convergence -- to pack in more detail -- and it still rendered in only 3 minutes 25 seconds. That's over a minute faster than the original, and hours less than if I'd reset the lighting to be that dark at typical render settings. My only postwork was to resize the image to match the original 1000x1300.

If you've wanted to render dark, moody, nighttime scenes but balked at huge render times and grainy images ... try the trick that movie directors have used for decades: shoot Day for Night!

Finding this years later withou the original Tone Mapping image setting feels like i missed out on some genius.
but ill try to put it together from the text and see what i can come up with.

isabel.ac.soriano

It has been a few years since this was posted, but I cannot appreciate enough this tutorial. I was so frustrated with the noise on my renders, but this has worked like a charm. There is barely any noise now. Thank you!