Lighting is one of the hardest, yet most fulfilling parts of computer graphics (in my opinion). Often artistic notions such as 3-point lighting are utilized to overcome the difficulties of lighting. But there's also another side of lighting, the side that strives to mimic the real-world as closely as possible. The backend of Cycles is doing a pretty good job for us, but there's a number of ways we can help Cycles along with this.
So in this article I'm going to cover seven ways to improve the accuracy and realism of lighting in Cycles.
Let's get to it!
1 - Accurate Brightness
One of the first things one thinks about in lighting is the brightness or intensity of the light. For good reason too, the brightness of a light can control the harshness of a light as well as how much indirect light is bounced from a light source. So to achieve optimal realism from lights, a proper intensity and exposure scale is needed.
Proper intensity can be achieved by using real-world values in combination with an accurate color lut that allows for control over exposure. For more information on this, you can check out my case study on Using Physically Correct Brightness in Cycles.
2 - Proper Scale for Accurate Shadows
The size of a light is equally as important as its brightness. Size can change highlights and shadows, as well as the overall perceived brightness of a lamp. Larger lamps create softer shadows, and vice versa, smaller lamps tend to create sharper and more detailed shadows.
The size of a light can affect the sharpness of shadows
Larger lamps also generate more light due to the increase in surface area, creating larger and brighter highlights, while also increasing ambient light by having more surface area to bounce from. A large lamp also creates softer highlights compared to a small lamp with an equivalent light output, which can be more clearly seen on rough surfaces.
3 - Color Temperature
When creating lighting using lamps, it's often an overlooked aspect of realism to change the color of the light. Along with intensity and size, proper color is one of the main things that makes lighting look realistic to the human eye. So instead of using plain white light, try using a physically accurate color based upon the type of lighting you're trying to produce.
The temperature of light can dramatically change the mood of an image
To create these physically accurate colors, Blender has a built-in Blackbody node that outputs color based upon the Kelvin color temperature scale. Kelvin is one of the most commonly used units for color temperature, so it's quite easy to find a reference for whatever lightings you're trying to create. To make things easier, here's a reference sheet from Wikipedia for some common temperature values.
4 - Environment Lighting with plenty of EVs
It's a well-known fact that one should use high dynamic range images when using environment lighting to maintain shadows and highlights. But something often overlooked is the fact that not all HDR images are created equal. Different HDRIs have differing numbers of EVs (Exposure Values), resulting in differing ranges of exposures for an image. You might be wondering what an EV is exactly, one EV is defined as the result of combining one image with another of double the exposure time into one image, that then stores the information of both exposures and the ranges in between them.
Low EVs can give dull results lacking highlights or shadows
More EVs give sharper shadows and highlights
For photography, 3 EVs is generally the standard to develop a properly tone mapped HDR image. But for lighting using environment textures, these ranges need to be much higher to maintain proper contrast in an image. Otherwise, lighting will come out dull and shadowless due to the lack of pixel brightness / intensity information in the highlights and shadows of the HDRI.
To make sure this doesn't happen, a much larger number of EVs such as 12, or ideally, 24 EVs need to be used to maintain pixel brightness / intensity information. But not all HDRIs use 24 EVs, so it's important to check your resources for HDRIs to make sure you're getting the most accurate images you can. My personal favorite source is HDRI Haven which is a constantly growing collection of 24 EV HDRIs by Greg Zaal with some of the most reasonable prices I've seen.
5 - HDR Textures for Mesh Lights
A majorly overlooked option of Blender is the ability to use textures on mesh lights. This not only allows the usage of uniquely colored light but also accurate emission intensity by using HDR images of individual studio lights in the same way one would environment HDRs. Using these HDR textures you can get accurate color, brightness, and contrast all in one. Basically, you get to bring all the magic of IBL lighting to mesh based lighting.
The added realism of textured mesh lights can make it easier to create studio lighting
There's a number of sources for HDR mesh lights, but HDR Labs has a great collection of some of the best ones. As an added bonus, they also include UV mapped meshes to apply the textures onto. To use them, just import the .obj and apply the HDR texture to an emission material.
6 - Filmic Color Management
Chances are, if you are a part of the Blender community, you've heard of Filmic. This new Color Management lut has taken the Blender community by storm the last few months by offering an easy way to properly manage dynamic range in Blender.
The best feature of Filmic is its ability to properly display light intensity and exposure. Meaning it will allow Blender to render and display blown out areas with proper color and intensity, unlike the default Blender color management that due to clamping, gives improper and often ugly results for bright areas of an image. This directly relates to how a scene is lit as well, giving freedom to the user to have brighter lights while still retaining proper color and highlights.
The default color management allows for high intensity lights to blow out highlights
Filmic preserves the details of highlights and shadows for proper grading in post
To use Filmic, all you need to do is switch the View under the Color Management tab in Blender to Filmic Log Encoding Base and you're set to go! For more information of Filmic, I recommend reading this fantastic article by Mike Pan which covers the advantages of Filmic in more detail.
7 - IES Lamps for Accurate Light Falloff
Unlike traditional area or spot lamps that use a uniform falloff, IES lamps calculate the distribution of light from its source to account for the physical inaccuracies of real world lamps. This is especially useful for situations when either the light source is in frame or is used as a visual element in a scene.
IES Lights can add realism, as well as visual appeal
We can use IES lights in Blender by either using a quite old but still functional add-on developed by Lockal that enables the use of .IES photometric files from lighting manufacturers to create 100% accurate lighting profiles. However, I've found that the more attractive alternative is to create custom IES profiles using Cycles material nodes instead.
That concludes the list. I hope you've found some useful tips for lighting in there somewhere.
If any of these tips helped you in lighting a scene or project, drop a comment below. I'd love to hear about it!