<< One statement was a suggestion that in early photographs of paintings
dark yellows might print black; >>
Early emulsions were sensitive to blue light (and UV) only - this was true I
think until the researches of Vogel which led to the first orthochromatic
emulsions - without looking it up I think around 1890. These would of course
have been on dry plates.
How colours other than blue recorded depended very much on the actual nature
of the pigment in them - most will have significantly less than 100%
absorbtion at all wavelengths. Yellows which are visually identical may have
very different spectral distributions and thus very different tones on blue
sensitive film.
An extreme example would be a bright yellow sodium lamp - or an object
illuminated only by it - which would appear light to the eye but pretty dark
on film, as a very high percentage of the light output is in a pair of lines
in the yellow. Paint of the same colour to the eye would probably be a sort of
mid grey as it would reflect a reasonable amount of light in the blue region.
I'm not sure why you are asking the question, but the answer would thus have
to be that it depends on the particular spectral distribution in the yellow
object.
You can expose a blue sensitive material - such as Fine Grain Release Positive
- in camera (or by contact from a slide) to see the effect.
Peter Marshall
On Fixing Shadows and elsewhere:
http://faraday.clas.virginia.edu/~ds8s/
Family Pictures, German Indications, London demonstrations &
The Buildings of London etc: http://www.spelthorne.ac.uk/pm//pm/