Color grading means changing the color of your film to match your creative choices. Sometimes you are actually correcting an image. But most of the time? You’re creating a look. The term grading is a throwback to the film lab days.
In this article we are gonna cover fundamentals that you must understand about color—things that will benefit you as a director, even if you never grade footage. We will post other articles soon that get into more technical tasks like grading room requirements, display calibration, fun stuff like that. Without further adieu, let’s get started!
Every color we see is a combination of red, green and blue known as RGB. We see colors because of light. Another word for light is luminance. Color is a three-dimensional thing. We have hue, the actual color itself. Saturation, the intensity of the color and luminance, the brightness of the color.
If I had a CU shot of a red apple in my movie and I took that to the color page and didn’t touch hue—the actual color—but changed saturation or brightness, it would affect how the apple looks to the audience. So there are many ways to work with your footage to dial in the look you want for your film.
Color spaces can be pretty confusing at first. Before we dive in: If you know anything about cinema cameras, they have a dynamic range. Dynamic range is what the camera can see from the darkest darks to the brighest brights. It’s the range the camera can capture.
The human eye has a larger dynamic range than cameras do. As beautiful as a mountain range might be in a movie, if you were there in real life, you would see more details in the brights and shadows than you did in the movie. Make sense?
Colors are similar. The human eye can see a very large area of color—back in the 1920s, scientists did a bunch of experiments to plot out the colors the human eye can see. In 1931 they released what’s called the CIE Chromaticity Diagram (shown above). This diagram is still used today.
Back to the dynamic range example above, a color space is a similar concept. A color space is the “range” of colors that technology can capture or display. A certain camera can capture colors that make up a certain color space. Other cameras are able to capture more. Same goes for TVs.
Color spaces have specific chromaticity coordinates on a CIE chromaticity diagram. For example, the video version of this article (linked above) is in the Rec. 709 color space. Rec. 709 on the CIE chromaticity diagram is here:
Rec. 709 is only about 35% of what the human eye can see. And wanna hear something crazy? All of those gorgeous HD Blu-ray discs we jumped to as we tossed our DVDs? Those HD Blu-ray movies are in the Rec.709 color gamut.
Quick answer: No, they are not. If you plot out a color space mathematically, it’s a three-dimensional object. The chromaticity points we see on the CIE chromaticity diagram only account for part of the color space. And they are referred to as the color gamut of the color space. Refer to the image above. The yellow border defines the gamut.
Color spaces also have a gamma curve which deals with luminance values. For example, referring to the video version of this article, the color space is Rec. 709 gamma 2.4. While another video you see online could be gamma 2.2.
In summary we have a color space with plotted RGB values called the color gamut. And this also has a defined gamma curve. Just know that Color Space and Color Gamut are not technically interchangeable. A color space has a color gamut. And the color gamut is the 2D reference of where the color space exists. Sometimes however, they’re used interchangeably.
A practical way you’ll see color gamut used is to define what equipment can do. For example, if you go to B&H Photo and search for displays, you can filter based on what color gamuts they support. You’ll see things like, “Hey, this display has 100% Rec. 709 support and this one has 99%.”
What does this mean? It means the display with 99% support has a smaller working color gamut on the CIE Chromaticity Diagram than a true Rec. 709 display. When we’re grading, we want displays with 100% support for the color space we’re grading in. This brings up another question:
How many color spaces are there, and how do you know what to grade in? Great questions. It’s actually easier than it sounds, but before we go there, we need to discuss SDR and HDR: Standard Dynamic Range and High Dynamic Range.
Standard Dynamic Range can be viewed as a “container” for color spaces. Not an actual container, but a conceptual way to group color spaces. A label of sorts. Rec. 709 is an SDR color space. So is sRGB.
Rec. 709 is the color space used with HDTV and 1080p Blu-ray players. The Rec.709 color space is SDR. But what you must understand: Pixel count and color spaces are 100% independent of each other. There are countless numbers of 4K TV and films in Rec.709—It’s not about resolution.
What confuses this is the fact that SDR came about alongside HDTV. And HDTV displays cannot support HDR.
Rec. 709 is an SDR color space. Rec. 2020 is an HDR color space. HDR tech was released alongside 4K and 8K TVs. Again, not because of resolution. Because of simultaneous advancements in tech. We know where Rec.709 sits on the diagram. What about Rec. 2020?
HDR color spaces cover A LOT more than SDR right? When people go to a Best Buy and watch content on 4K and 8K TVs it looks “so amazing.” But it’s only partially due to resolution. It’s because these new displays also support HDR. And the content Best Buy is playing is HDR content. You know, bright green lizards on pink flowers that really push the color landscape.
So again, you’re not being wowed by 8K as much as you’re being wowed by HDR. There are different HDR color spaces out there: Rec. 2100, Rec. 2020, P3, etc. And just like Rec. 709 various equipment has different levels of support for these color spaces.
Back to our question: What color space should you color correct in? The answer is DaVinci Wide Gamut (DWG) if you’re using DaVinci Resolve. DaVinci Wide Gamut is a very large color space that can house other HDR color spaces. Meaning it’s larger than Rec. 2020, etc.
So we shoot our movie and grade in DWG. Good. Done.
Well, not so fast.
To accurately grade in HDR, it takes a lot of money. You’re gonna have to purchase expensive hardware for your computer, along with an expensive display with full HDR support. Computer displays that have 100% support for HDR at a grading level cost A LOT of money. And if you’re not grading accurately in HDR, you might be doing more harm than good.
If your film is destined for online viewing, or at home viewing, monitoring and delivering in Rec. 709 is absolutely fine. There’s tons of content delivered with Rec. 709. You should grade in a DWG timeline so you have access to HDR tools in Resolve and can grade your film without restraints. Resolve will then graciously take that to SDR for monitoring (what you see on your display) and delivery. And then if you do upgrade to HDR hardware you can simply open the film back up, tweak your grade and deliver in HDR.
So that was a lot of geek talk about color grading. What are main takeaways?
Hopefull this has been helpful. If you have a cinema camera like the Blackmagic Cinema Camera 6K then you are shooting with HDR support. You can then bring that into DaVinci Resolve in a color managed project using a DaVinci Wide Gamut (DWG) timeline. This allows you to grade your footage without restraints and with access to HDR tools in Resolve. You can monitor and deliver in Rec. 709 or if you have the hardware support, monitor in HDR and deliver your film as needed.
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