Pseudo-what? I hear you ask. It sounds very complex. And it is. It’s a problem that can afflict black and white prints, especially those produced using inkjet technology. It’s also known as Grey Balance Failure or Colour Balance Failure.
Simply put, it’s the phenomenon whereby a black and white print can appear to have a colour cast in some lights, but not others. Moreover, the colour of the cast can appear to change under varying lighting conditions, most often appearing as either a green, pink or magenta tinge.
Part of the problem is that inket and commercial photographic printers actually print black and white photos using colour inks – cyan, magenta and yellow, along with black (because no amount of mixing coloured inks can produce a genuine black, just dark brown). These printers are typically configured to produce ideal results under what is called D50 lighting, which is a illumination standard that correlates with “horizon light”, with a colour temperature of 5003 Kelvins – roughly daylight. However, as you move away from this standard illumination, into light generated by, say, tungsten or fluourescent sources, the energy levels at different frequencies can change. Along with that change, the light reflected by the dyes or pigments in the ink can also change, resulting in a slight colour cast. The colour depends on how the inks react to different lighting situations. In some cases it might be pink or magenta, in others it might be varying shades of green. In other lighting situations there may be no colour cast at all. It depends very much on the lighting source and the inks involved.
And it’s not just inkjet prints that suffer from this problem. It’s also been noted in chromogenic colour prints as well (conventional prints that are produced using light sensitive emulsions and developed using chemicals).
Solutions vary. If you’re printing at home with an inkjet printer, consider using only black and grey inks. I’ve also read that matt prints perform better. If you use commercial printers, try shopping around for companies that offer specialist B&W services.