from gray card to color bars chart.
 

In my early years of passionate amateur for photography I was devoted of Ansel Adam's statements of the gray card as the base for reading the light. Today, I see the color bars chart is the technic for measure the light and calibrating the video cameras. Could someone explain me:
1. What's the difference?
2. How are the benefits to improve my videography?
3. How can I use it?
Thanks.

The 18% gray card is still completely usable as a means to judge exposure (43-47 IRE is the ideal target I think) and it is also perfect for white balance either in-camera or in post. What I really like about 18% gray cards is that you can still find them in 2-packs at any professional photography store for under $10.

Charts like DSC's ChromaDuMonde take it to the next level and allow for precise adjustment of RGB matrix controls. The more colours on the chart the better.

Working (previously) in a broadcast studio with a multi-camera set-up I never used colour charts (as opposed to generated NTSC colour bars) for calibration. Greyscale chipcharts (very expensive ones, I might add) was what we used. To calibrate to NTSC standards, that's what you need. Actually, come to think of it, AFAIK NTSC colour bars can't be accurately produced in print -- at least that's what my former boss told me.

Of course, if you are looking to apply some sort of stylistic treatment to your footage, the colour charts come in handy (as Tim already mentioned). Broadcast calibration and stylistic treatment are two different ends that use slightly differing means.