BARCO Tech Tip: The World in Color

Publish date:
Social count:

In light of the convergence of Barco and High End Systems last month (pun intended), I thought it might be nice to review one of the key differences between the way the lighting and video guys look at color. These two visual mediums view the production of color in one of three main color spaces: CMY, RGB or YUV (SMPTE).

Cue the Lights
Lighting generally utilizes the CMY (or CMYK) color space, which works on the premise of SUBTRACTIVE color mixing. CMYK stands for Cyan, Magenta, Yellow and Key (Black). To achieve the desired color, CMY starts with white light as a background color, and then uses variable amounts of the three colors to mask out color wavelengths. For example, mixing yellow and magenta will net you Red. Black is achieved by turning off the light, and not by using all three colors to mix to black. When you try to subtract out all the colors, you generally get mush and not true black.

Adding Video to the Mix
Whereas the CMY model is subtractive, the RGB model (as used in video) is an ADDITIVE color model, which works as light is emitted directly from a source such as an LED or CRT. By combining the three primary colors (Red, Green and Blue) in varying amounts, you can achieve any color under the rainbow. The absence of all primary colors in this color space yields black, and all three primaries added together at full intensity will produce white light.

Unlike the CMY model, the RGB model is device dependant. Different technologies will reproduce the R, G, and B elements in a unique fashion. This accounts for color fluctuations between LED, DLP and LCD technologies. Each one produces the three primary colors in a different fashion, and thus each represents a similar image differently. To maintain a uniform color match between RGB devices, you must use some type of color management tool, like a color meter, to match the devices together. Literally, the ability to adjust color within the display device is what separates professional equipment from consumer level gear.

Lastly, video also uses the YUV / YCrCb color space. YUV is used for Analog signals, where YCrCb is used for digital signals. The Y stands for the Luma (or brightness) component, while the U and V represent the chrominance (or color) components. In essence, black and white television was just the Y or Luma value without any of the color values.

To achieve the correct color mix, the U and V components are subtracted from the Y value. For example, the U signal is created by subtracting Red from Y, which yields a mix of blue and green. Conversely, the V signal subtracts blue from Y, and yields a mix of red and green. By adding all three values together, we achieve the correct color mix for the image.

The reason we use YUV is to create a means to mask any transmission or compression errors that can occur during broadcasting. YUV also requires less bandwidth for transmission or storage.

Bringing It All Together
As the video and lighting convergence continues and strengthens, each side will need to adopt the color language of the other. By doing so, we can effectively mix technologies on the same stage and achieve the look that our clients are paying us to achieve. The challenge is clear, and getting to the same color from two departments will require tweaking, color management and a keen understanding of each color space.

For example, in the CMY world, achieving pure blue requires a non-equal mix of cyan and magenta, while in the RGB world, pure blue is a primary color and easily achieved by not adding in any red or green.

As lighting manufacturers adopt more LED and other traditional RGB devices in their lighting fixtures, and as video manufacturers create new moving head projectors that bring RGB color mixing and digital gobos into play, the line between the worlds will continue to blur.

It will be interesting to see how the two worlds continue to mix as the paints we use start to originate from the same palette.


Image placeholder title

Barco Tech Tips

Tech Tips is sponsored by Barco, and offers insights into techniques and equipment employed by stagers working in the corporate and entertainment event market. For more information about Barco products, log onto the world of seamless switchers, the term KEY refers to a process in which part of one video image is mixed on top of another video image. Seamless switchers switch and convert multiple sources with various resolutions to a common resolution. The KEY effect in these devices is most commonly used to add titles to camera images. Another use of this effect is referred to as "Green Screen" in which an actor is filmed in front of a flat Green or Blue wall and then inserted into a virtual environment or in front of a weather map.

BARCO Tech Tip: Switch Hitter

During a recent meeting with a new client, I introduced our product line to the heads of their video department. While taking them through our seamless switcher product line, one of the team members expressed the lack of "quick switching" as the reason for not using that type of product in their workflow.  Their typical show solution was to sub-switch graphic sources "upstream" of a basic video production switcher.

BARCO TECH TIP: Getting Graphical

The last couple of "tech calls" I've taken revolved around what type of graphics card the customer should select for some specific applications. When I answer these questions, I tend to take a "Switzerland" approach, and answer in very general terms and performance standards. The bottom line is that each graphics card manufacturer offers a unique spin on the same concept: delivering pictures from your PC to a display.

BARCO TECH TIP: Cable Wisdom: The Good, the Bad, the Repairable

It all started with a note from a friend. I received an e-mail last week from a longtime buddy about video cables. Specifically, he wanted to know if RG-59/ RGB cable ever goes bad. If so, when should he replace it? It was at this point that I wished I worked for one of the fine cable manufacturers we all know and love. Maybe that is why he asked me, instead of one of the fine cable manufacturers. In any case, I rattled off the answer that I imagine most of you are thinking right now: Cable does not go bad.

Image placeholder title

BARCO Tech Tip: DVI Demystified

During one of my "dog and pony shows" last week, a question floated my way concerning the differences between the multiple DVI connectors out in the world. In answering this question - and cognizant of the fact that my deadline for this article was a mere three days away -- I chose to make this month's Tech Tip a discussion of the realities of DVI.

BARCO Tech Tip: Go Forth and Educate Thyself!

One of the best "tech tips" I can provide is to take a few hours each month and learn something new about our industry.  This education can take many forms.  For example, one could take a formal class, such as a manufacturer's training session, attend a meeting of one of the many professional associations that support the events market, or simply spend time on the web researching and browsing on various association web sites.

Barco Tech Tips: 220...240 -- Whatever It Takes!

When you're tasked with selecting a frame rate for your seamless switcher's output, many people adopt the same attitude as Jack Butler (Michael Keaton's character in the 1983 film Mr. Mom). To paraphrase Mr. Butler's memorable quip, "59.94 Hz or 60 Hz...whatever it takes." In most professional seamless switchers, there's an excellent reason why a choice is provided between these two (seemingly close) frame rates -- and the reason is not quite as random as "whatever it takes."

Solving the Color Sampling Ratio Puzzle

As our industry dives headlong into the digital video domain, content producers and video engineers find themselves dealing with color sampling ratios on an ever increasing basis. In a nutshell, a "color sampling ratio" is a precise numeric method of describing the relationship between the luminance and chrominance values in a digital video signal. Currently, there are many digital video formats in use, none of which are "perfect," and all of which include some form of signal compromise.