I use an old-fashioned red bulb, 25W I think, at the other end of the darkroom. It is a lot brighter than the near-invisible green light I use otherwise - but terms like "strong" and "bright" are relative.Originally Posted by jjstafford
It is surprising to many how much light it really takes to fog film, human eyes are certainly far more sensitive to low light levels than 25 ISO film!
No simple light filter is perfect, an certainly not HAMA's coloured light bulbs. But with a little forethought it is very easy to avoid fogging: Remove film from holder in darkness, start developing in darkness, do not turn on light until you are getting close to the expected end of development. In most cases you will find that the colour of the light matters not at all - it might just as well be white as long as it's weak enough. But when some films have reduced sensitivity in some part of the spectrum, I consider it a good idea to exploit this by using a light sorce which is centered around this part of the spectrum. So whether or not I can see farther into the red than the EFKE PL25 film can is irrelevant, since neither I nor the film can see the longer wavelengths that the lightbulb gives off. Good enough reason for me to use red light when developing these films by inspection.
Where did you find that information? I couldn't find it? Most sources seem to agree that the visible spectrum extends to just short of 700nm, with people operated for cataracts seeing as far as 780nm. No, I haven't had cataracts, so I don't expect to see into the IR.the young, healthy human eye cannot see above about 640nm, and the aged eye even less