Compromise between Color Accuracy and Signal Noise

Walt_Lindblom1 E2 CR 400W

Walt Lindblom

Video Engineer with SAIC
NASA DTV Program

At NASA our objective is to capture the highest quality and most accurate images possible. However, there can be a trade-off between color accuracy and overall image quality which impacts on how the cameras are aligned and the original image is captured. These decisions are important because the images will live in the NASA archives forever.
When using the ChromaDuMonde CDM-28R chart, we have found that bringing all of the color chips to full saturation can cause problems. Specifically, extending the response of the green and cyan chips up to full saturation can cause noise on some cameras. While full saturation on all colors results in the most accurate color reproduction, it can introduce more noise than is acceptable for our purposes. We have found that a reduction of about 20% in green and cyan saturation (moving the green and cyan signals 1/5 of the distance towards the center of the vectorscope) is a good compromise between color accuracy and signal noise. We maintain the polygon shape DSC shows in their instructions. This results in slightly reduced saturation in green and cyan, but it is still extended response in green and cyan when compared to the factory setting of any camera we have checked to date . We feel that the slight reduction in green and cyan response is beneficial overall as it still provides very accurate color reproduction and produces less image noise, which is exceedingly difficult to remove later.