I have both versions. If I can get to it today I'll do a test and compare. The general perspective is the difference is minor. But we'll see.
Steve Hendrix
After testing a Phase One 120mm/4 D Lens and a Mamiya 120mm/4 non-D Lens Friday afternoon my conclusion bears out the prevailing consensus; that the two versions are very, very close (see attachments). The Mamiya 120/4 has always been one of the best 120mm macro lenses for medium format. There just wasn't a whole of improvement that could be done with the lens. Nonetheless, it's understandable that the process of improvement from the original Mamiya lenses to the upgraded D versions was applied and is continuing to be applied to as many lenses as possible. I suspect that the degree of improvement may be an unknown factor until the finished product, and at that point, with the R&D invested, why not certify it as an upgraded model? There certainly has been significant improvement in some of the lenses from non D to D.
We've posted our 150mm comparison time and again, but here once more...
http://www.captureintegration.com/tests/lensI've seen somewhere MTF charts comparing the Mamiya legacy glass to Contax Zeiss and Hassleblad Zeiss and the Mamya legacy glass actually fared quite well to my surprise. But to be sure, there are some average lenses in the legacy lineup that have benefitted and will benefit greatly from the upgrade process. Most of the Mamiya complaints I've heard in the past have been more about build quality than optical quality. And all of the D version chassis are much more robust than the legacy versions.
Steve Hendrix
[attachment=22582:Mamiya_120_non_D.jpg][attachment=22583:Phase_On...0_D_Lens.jpg
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