If you take your original image and try subtracting between 0 and 10 points (out of 100) in the blue and/or red, youd should start to see the differences in colour rendition as the result of consequence of the kind of differences in the transmission spectra we are talking about. It will be interesting to see the results.
David
That's what white balancing is all about, balancing the levels of red, green and blue channels
to avoid any disturbing tint/cast on the final photo due to the color temperature of the ambient light.
No need to be too theoretical, rather than heuristic in this case I think,
though transmittance and black body spectrum can be interesting in some contexts.
Since the color temperature of the ambient light is constant in the test shots,
the amount of white balancing adjustment needed will instead reflect the transmission levels/color bias over the visual spectrum in the binocular.
What you could argue about is that the light source doesn't have constant intensity over the spectrum, having too little blue content, or that the digital camera used was crap, might be, but at least it's non-biased...doesn't care if the motive is a Zeiss or Leica view.
Nevertheless, I think this method gives us a hint about what is going on and that the "color bias" differences between modern alpha bins are quite modest.
It was much worse in the past.
And color bias would actually be one of the minor points to
consider when buying a new alpha bin.