Hue, Saturation and Value in Color Grading

If you color grade in film or video you are probably familiar with the terms Hue, Saturation and Value.

[Value is also sometimes referred to as Luminance. Although there are some slight differences between their definitions, in practical use they are synonymous. We can argue about it some other time.]

These are the three attributes of color. In order to manipulate color methodically or precisely an artist or colorist must be fluent with them.

Hue is the location on what we commonly call a color wheel:

Saturation is the relative strength of the color:

Value is the relative lightness/darkness of the color:

[Note: The above illustration is derived from The Zone System, developed by Ansel Adams and Fred Archer around 1939. Anyone working with either shooting film/video or color correction and grading should be on intimate terms with it.]

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Color Correction

The intersection of these three attributes creates what we call color. ‘Color’, however, is too vague a term to be of much use by itself. The more you can think in terms of color attributes, the more clearly you will think about the work you are doing.

Most of us are attentive to these attributes in the process of color correction or primary corrections, so let’s consider the best workflow. The acronym HSV suggests a workflow sequence, but it’s not a very good one. The best way to approach correcting color (that is, balancing tonal inconsistencies, removing color casts, creating continuity between shots and scenes, etc.) is not ‘HSV’ but ‘VHS'. Instead of first correcting Hue, then Saturation, and finally Value (HSV), it is much easier and more efficient to first correct Value, then Hue, and finally Saturation (VHS).

If you are not a fluent translator of color to values then the best way to begin a correction is to work in monochrome on your first pass through the footage. Then bring saturation back to normal to work through the hues. If, after values and hues have been balanced, there are still issues getting footage to a neutral, matching state, the only remaining variable is saturation. It works.

The following illustration shows the three attributes of individual colors imagined as though they are controlled by sliders. Adjusting these attributes to neutral levels is how I approach color correction.

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Color Grading

Proactive application of this theory in the color grading process (creating a look) can be immensely helpful to the colorist, as it not only encourages the artist to look globally at the shot, the scene or the entire project but also adds structure and methodology to the grading process.

This will not solve everything, but done thoroughly it will create a solid foundation for detailed, contextual tweaks. An important caveat is that color - by itself - doesn’t exist. In a world with only one color, only value and saturation matter. ‘Color’ as we know it only exists in relationships with other colors.

A color which appears ‘green’ to most people in one context will appear ‘brown’ in another and ‘blue’ in yet another. What is clearly emerald green in an OTS may appear aqua in the reverse because of changed relationships with surrounding colors. Globally (a change affecting everything in the frame) modifying the attributes of color in a shot/scene will not always be the final point of a grade. It may still be necessary to modify individual colors to create the color relationships desired, but it will set the stage for those specific modifications and simplify that final stage of the grading process.

When modifying multiple colors in relation to each other the three attributes of color are proportionately connected.  Changing the value of one attribute changes the optimal values of the others. Simply put, more of any one attribute requires less of at least one of the other attributes.

Modified for global color changes, our sliders now look this:

In this version of the sliders you see that the hue spectrum has been replaced by ‘# of hues’ and ‘lightness/darkness’ has been replaced by ‘contrast’ (distance between lightest and darkest values). This reflects the fact that we are no longer simply modifying a single color by its attributes but are now modifying a shot/scene with multiple colors that relate to each other.

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So how does this work in practice? Let’s look at a few examples, starting with a composition containing a wide spectrum of hues. A wide spectrum would require either changing saturation or contrast, maybe both. It might look like this:

In this painting by Pierre Puvis De Chavannes (War, 1867), Chavannes uses precisely this approach of many hues, medium contrast and very low saturation in order to keep compositional unity and focus on the important part of the image:

Another example of the same approach by Chavannes:

This is an approach very commonly used in contemporary film - it is often called ‘the film look’. It has the great advantage of unifying compositions/frames almost effortlessly.

Another approach to the inclusion of a wide spectrum is to suppress the value scale in order to keep a wide spectrum of hues yet retain strong saturation, which would look like this:

The example below is a painting by Paul Signac, Portrait of Felix Feneon, 1890.

Signac is all around the color wheel in this painting but look closely at how he pulls it off. First, note that the value range is very compressed - there is little approaching pure black or pure white. Even the top hat is not pure black but dark gray. All the hues are similarly pushed towards the middle of the value range, even the yellows.

When desaturated, this management of tonal range becomes very obvious:

The values of many of the colors are nearly identical (the reds, yellows and blues on the right, for example).The brightest point is the lily and that is nowhere near pure white. The tonal composition, however, is clearly designed to lead your eye to the center. Note also that all the colors remain very saturated.

This approach is very close to classic Hollywood color: lots of hues, strong saturation, but a carefully compressed value range where nearly all values are pushed toward the middle of the scale. There is a little more of real black to the Hollywood version, but nearly all the other values - including the light on the wall - are pushed towards middle gray.

In all three of these examples from classic Hollywood films, we can see in the gray scale versions exactly where the focal points are through the value composition. In the example at the top (Desk Set), it’s the woman in the center desk. In the 2nd example (Seven Year Itch), it’s the two figures in the center of the frame, in the last (The Man Who Knew Too Much), it’s the three figures in the front, the only points in the frame with real white. In all three we have strong, saturated color, but the color is not distracting because of the strict control of values.

In contemporary film (as well as many contemporary commercials), another approach seen more and more is many hues balanced by both low contrast and low saturation so the final product is very, very flat. Although it is sometimes an appealing look on its own (especially combined with a warm/yellowish wash and lens flare for a retro look) it has the additional advantage of being able to unify nearly any frame or sequence. If you must shoot with little control over location, art direction, stage dressing or production design (as many low budgets and indies must), it is a very forgiving approach to a color grade.

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The practical question is ‘how do I make this theory work for me?’ Obviously when looking at big budget features, these strategies are decided in pre-production but they are also available - and useful - to filmmakers without those resources.

Look at your source material. What problems must be solved? What look best fits the story? Are you struggling with a wide spectrum of hues throughout? Would it be appropriate to solve that problem through limiting saturation and/or value?

Or is it necessary to keep colors saturated and vibrant? In that case, can you push values towards the middle of the scale?

There are dozens of ways to interpret color attributes depending on the source material. These are only a few illustrations of color strategies. In other posts I’ve examined the Orange and Teal approach and the concept of the Limited Palette - a way of controlling the use of very strong color.

Happy Grading!