Color Bar Symmetry

CG CHARLIE_WORKING_CDN IDOL 1AW

Charlie Goldman
Charlie Goldman is a leading video engineer on popular shows such as Canadian Idol, Cirque du Soleil, etc.

Producing consistent accurate color reproduction can be a challenge, particularly under different lighting conditions. Whether I am shooting the Olympics, Rock concerts, or Ice hockey I use the same basic technique.

It is helpful to understand the engineering behind DSC colorbars. All DSC color chips are mid saturation and represent real life colors. Each color is designed to produce levels of 80 and 40 IRE analog or 560 and 280 mV digital. An increase in vectorscope gain of 1.875 will put all the signals in their boxes when a camera is aligned for accurate reproduction.

In analog systems, this simply means increasing vectorscope gain to position the burst opposite the outer corner of the yellow box, then adjust the matrix to set CamAlign’s RGB and CMY color chips in their boxes. A number of scope makers now incorporate the 1.875 factor for DSC charts in their new digital scopes or provide a calibrated readout of gain level.

Older digital scopes do not have a calibrated gain function, so in these situations I adjust the matrix to produce Red chip waveform levels of Red 560mV, Green 280mV and Blue 280mV. I then match the other colors to the same saturation on their appropriate vectors. Be more concerned with the lower values than the higher, because errors at the 280mV levels will have a much larger visual effect than variations in the 560 mV level. Dave gave me this tip years ago, told to him by a Sony engineer in Chicago.

Charlie Goldman will be featured in an upcoming “Spotlight” at http://www.dsclabs.com/