I was wondering how consistent the density and colour balance of the orange mask used in colour neg films is? Years ago I standardised on the now obsolete Fuji Reala for colour neg film for medium format. My enlarger (Durst Modular 70 + Colour Micro head) has separate calibration channels for different types of film. The assumption being that the filtration offsets required for a particular type of film do not change significantly between batches. Calibration involves making test prints from a neg of a kodak grey card, measuring the print density and adjusting filtration until you get a good colour match between the print and the original grey card. In my experience, the mask used on Reala has been reasonably consistent. However, I have had at least 2 batches where the mask is very different and requires considerable changes in filtration. In particular, the last three films I've had processed appear very different to negs from a few years ago. The difference is quite marked - even when comparing visually. It can make adjusting filtration frustratingly difficult if you don't happen to have a grey card image on the particular film batch you are trying to make prints from.