Hello Edward,
in this sector, there are manly two guidelines: FADGI (American guidelines) and Metamorphose (from Nederlands).
FADGI suggests
Adobe1998, ProPhoto or ECIRGBv2 while
Metamorphose only ECIRGBv2.
I am not sure regarding the rationale of these choices.
given systems where textual information & facsimile, from viewpoint of easy reference, are the desiderata, the rationale for ECIRGBv2 seem very sound to me.
if i understand the term «master» correctly, i think both sets of guidelines too weak for aesthetically critical work: i should always scan at much higher resolution & convert to lab,
repurposing for whatever requirements the future may present—i believe this the best investment. but, [real] scholars will always need to handle the originals, anyway.
So the first point is that ECIRGBv2 is the only one that is accepted from both.
I would like to use the large gamut of ProPhoto but because these master files will be 24-bit images (8-bit per channel) so using ProPhoto could result in posterization effects furthermore is not well established.
Adobe1998 would be quite a good choice because of its larger adoption, but in the case of manuscripts that have many red inks a larger gamut in the red I think could be beneficial.
ancient pigments can contain many out-of-gamut components. while Adobe1998 has deeper red space, have you compared input profiles of equipment under consideration to both? you may be contemplating reds that your scanner
won’t see, anyway.
Regarding the equipment, we are deciding between some scanners e.g. Metis DRS-13000
and Phase ONE cameras.
Let me know if you think there is something I have missed!