I wonder whether this new Phase One 150mm f/5.6 telephoto lens is an evolution of the renowned 1995 Mamiya N 150mm f/4.5 lens for the Mamiya 7 system, also a telephoto design.
Here is the cross-section of the Mamiya N 150mm f/4.5 lens, adapted from the Mamiya 7II instruction booklet:
View attachment 210915
Mamiya's description of the lens stated:
The Mamiya 150mm f/4.5 is a moderate telephoto, using a unique design of six elements in five groups, along with low and ultra-low dispersion glass to create apochromatic performance matched to the entire group of Mamiya 7 lenses. Applications include portraiture, fashion, landscape and aerial photography.
What stands out to me in that cross-section is the use of four elements in the front group, rather than the traditional three, given that the focal length is a relatively short 150mm. Particularly as the maximum aperture is a modest f/4.5 rather than, say, f/2.8. At that time, four elements up front were usually employed in telephoto lenses of 300mm and longer, not 150mm. That group of four will contain perhaps two elements made from the low and ultra-low dispersion glass noted by Mamiya in its description.
At the time, I recall that someone who tested the Mamiya N 150mm f/4.5 called it the sharpest lens in all of medium format.
Given that Mamiya was bought by Phase One, it's at least possible and perhaps likely that Phase One has decided to revisit and rework one of the earlier Mamiya 7 lens designs. Despite the reduced maximum aperture, the number of elements may well be increased to boost the resolution further. It will be interesting to see if the optical cross-section of the new lens shows any is resemblance to the earlier lens.
Rod