CompuServe Messages

Color bars come in two basic varieties, NTSC and SMPTE for NTSC video. Both have the same colorbars but the SMPTE has additional color and luma calibration bars. These bars should be generated by the same device as your program video when recording to tape. eg. If shooting from a tube camera to a remote tape recorder you would generate the bars from that camera. When shooting from a chip camera you would generate bars from the chip camera. When generating video from a PAR or frame buffer you would lay down bars from that video source. In this way the bars (color reference standard) could be used to calibrate the video timing just before recording and make allowences for any deviation from standard at a different post facility. The bars that I uploaded some time ago were intended to be used by those with a targa+. The PAR comes with its own set. Here's how I would use them in post. I receive an A-roll tape shot with a camera and remote VCR. The bars look a little off and all flesh tones are on the purple side. The magentas are orange. I have a B-roll tape that was shot with a different camera and docable betacam deck. The colors look perfect and the bars look good too. Next I pick up a tape of graphics done in an animation post house which has bars generated by my "bars" file. However, they seem a little shifted too. The yellows look green. In post I feed the bars signal from each tape machine and adjust the chroma phase until each tape sends the standard bars to my monitor making note of the adjustment for each tape. The monitor sees the video signal just before and right after the edit VCR. Now a particular Yellow will match on each tape when I mix the video in my A/B/C roll edit. If the camera person were to record bars onto a tape from a signal generator and then assemble edit the scenes in the camera the bars would not be representative of the camera's signal. If you are not able to generate the bars in the camera then shoot the bars from a test chart. Bottom line is that the bars should follow the same signal path as the program video when recording to tape.