As originally envisaged by Kodak, the PCD scanning process (and specifically the SBA or Scene Balance Algorithm) adjusted the scan parameters to get an optimal image, color rendering to a single standard, and adjusting exposure, contrast, etc. In practice, there are a number of problems. Firstly, the SBA required that film type be correctly identified. However, even if the film type was correctly identified, SBA's white balance algorithm was relatively easily fooled, and was often disabled. In addition, over the life of the Photo CD format, at least two different generations of scanners were used, and several versions of SBA were used, with different results. You can check the SBA status for each individual image in the metadata information that pcdMagic prints out. As a result, in order to get optimum color rendering, film and scanner specific profiles are required. Kodak eventually release six profiles (Kodachrome, other reversal and negative film stock for each of 4000-series and 2000-series scanners)