> Except that we didn't use red light in our
darkrooms at all, at
> least not from the 1970s and on. ...
Correct. I started darkroom work in 1964, and from
the beginning we
used amber safelights. I don't think red safelights have been used
since long before that. Another thing that the film industry
continually gets wrong.
It really isn't true that red filters quit being used. Some materials
are not sensitive to the broader spectrum of an amber light, making it
feasible to use one. The broader spectrum is probably easier for many
people to work under. Some manufacturers recommend amber safelights on
the strength of improved working conditions even for materials where an
amber safelight is marginal.
But some materials _are_ sensitive to parts of the amber, or even to the
whole visible spectrum, and other types of filter (or even no light at
all) must be used.
A quick perusal of B&H stock indicates that lots of red safelights are