Calibration curve, from various literature

Digitization of calibration curves published in literature threw somewhat of a wrench into the one parameter idea. It seems like EBT calibration curves differ by a huge amount. Since extracting the red channel amounts to integrating over a segment of EBT's transmission spectrum, we expect variations due to different scanner lamps, but data from Epson 1680 and Epson 10000, which are the same class of scanners, show huge differences. Without knowing details of other authors' film protocol, we can only speculate that the variation in film sensitivity is the main reason behind this difference. As usual, more data is needed... Stay tuned for more digitized data. For the record, I use the software "GetData", which is quite convenient, and has 30-day trial period. The full version will cost $30, which is quite reasonable.