DSC Labs Charts: A Precision Tool for Cinematographers
The benefit of using a DSC Labs' ChromaDuMonde chart became abundantly clear to me six years ago when I developed the Goodman's Guide series (www.goodmansguide.com) for HD and digital cinematography cameras. For the Panasonic VariCam, I needed to illustrate the camera's ability to make subtle changes in color reproduction. I started out using the approach I had used since I began my career as a photographer and cinematographer.
Standard practice, then and now, when shooting film is to grab a few frames of a person's face next to an 18% gray card. To provide more information to the color timer who would grade (color correct) the film, you would substitute a color chart in place of the gray card.
Today, color grading is typically a digital process because digital tools offer endless possibilities to alter and correct all or parts of the image. However, many of us haven't changed the way we make our intentions clear to the people who will grade what we've shot.
Working on the VariCam Guide, I quickly discovered that my standard approach didn't work. The chart I had used for 20 years could not detect the subtle changes I could make by adjusting how the VariCam reproduced color. That chart wasn't precise enough for a modern HD or digital cinematography camera. It was clear I needed a more accurate color calibration chart. After researching my choices, I decided to go with the DSC Labs' ChromaDuMonde CamAlign.
The version I currently prefer has twenty-eight color chips, plus DSC's standard eleven-step crossed grayscale, 100% white and true black chips, hyperbolic resolution trumpets, and DSC's CaviBlack option. The CaviBlack, a hole in the chart, with a folding black fabric light trap behind, makes setting black levels and adjusting the camera's RGB flare settings simple. The twenty-eight color chips include: six primary vector colors (red, magenta, blue, cyan, green, and yellow), three intermediate colors between each of the primary color (eighteen in total), plus four skin tone chips, which represent a typical range of human skin colors.
DSC's CamAlign charts are laminated on aircraft grade aluminum backings. The surface is easy to clean and the chart is extremely rugged. CamAlign charts undergo extensive quality control. Every color and grayscale chip is measured four times using custom spectrophotometers. This helps ensure that every chip meets DSC's critical standards. For HD TV, all colors are based on the latest International colorimetry standard ITU-R BT.709 (SMPTE 274M). Under typical operating conditions, DSC charts remain within tolerance until the chart reaches its recommended upgrade date.
Any adjustment I make to a camera is easy to see when I shoot a DSC chart and use a waveform monitor/vectorscope to evaluate the results. The chart generates a precise hexagonal-shaped display on a vectorscope. The first step is to adjust the camera's gamma correction setting using the CamAlign chart's crossed grayscales and a waveform monitor. Then, you can adjust the camera's matrix and color correction settings using the CamAlign chart and a vectorscope. Each of the chart's primary colors (red, magenta, blue, cyan, green and yellow) should be positioned inside their respective vectorscope boxes and the chart's intermediate colors are spaced to fall at equal intervals between the primary colors.
Using a DSC CamAlign chart during production is easy. Simply record a frame or two of the chart whenever you shoot a new scene, change lenses or alter the lighting. This gives the colorist or grader a consistent reference so he/she can work faster and remain true to your intentions.
CamAlign charts will improve your images and increase your productivity, paying for themselves over and over again. For less critical applications, DSC Labs makes a FrontBox series and CamBooks with four, five, or six charts in them. For news and documentary production, there are Camettes in two sizes.
DSC Labs makes precision reference charts that have patented neutral grayscales and accurate, consistent colors from chart to chart. Inaccurate charts create more problems than they solve. Since switching to DSC's CamAlign charts, I've been kicking myself for not upgrading my color management system sooner.
Robert M. Goodman is a cinematographer and author of the Goodman's Guide series of references for HD and digital cinematography cameras which are available at B&H and at www.goodmansguide.com.