The ULH-23 makes it possible to use Hasselblad Lenses (not H1) in combination with the Ultima 35.
Hasselblad lenses can be set manually to the desired aperture setting. The ULH-23 can only be used in combination with both Canon bayonet based SLR bodies and with Nikon bayonet based SLR bodies.
The use of a Hasselblad lens relates to your sensor size as the same focal length in 35mm format, so f.i. a 50mm Hasselblad lens will have the same perspective on a 1Ds as a 50mm Canon lens;
for the smaller sensors the maginification factor will apply of course.