Originally Posted by
sharpstick777
Barry,
I have defined a few basic Free-form design types based on corridor emphasis and distance width based on FF mapping we did. These are only possible in Free-form.
T Design = Distance clarity edge to edge (primary zone gain), narrower intermediate, narrow to moderate reading... Auto II (most Shamir), Seiko Succeed/Supercede, et al.
Free-form Hour-glass = A little gain in most zones, but not edge to edge clear in any one. Wide Distance (but not edge to edge), moderate int and wider reading. Its a balanced design, general purpose lens, with no single emphasis. and Comfort DRx and Physio DRx, Steath Pro SD/MD
Plus Shape = Reading and Intermediate are very wide, but distance is not. Distortion is essentially moved to the four corners, which balances spacial distortions, and effectively widens the entire effective corridor, which is more cylindrical. (Definity, Hoya iD Lifestyle)
Barrel Shape = Wide Intermediate, slightly narrower distance and reading. Basically instead of putting the narrow end of the progressive cone at the pupil, it turns it around and puts the wide end at top instead. Distortion is moved to both the top and bottom edges, but gives about 4X the distance width as most Plus lenses. Basically, its two corridors, stacked with their wide ends together. The Seiko Surmount is the only one in this catagory at this time.
V Shape= Edge to edge distance, wider intermediate, but very narrow reading. Ziess GT2-3D is the only lens in this catagory.
Fountain Shape = The newest design, its like a T shape but instead of the narrow part of the corridor at the top, the narrower point is lower in the middle between the intermediate are reading zones. The intermediate ends up being a little wider, with a little lower declination. Reading is a little lower. Distance is edge to edge, and because of the distortion being pushed down, and away from the central view, the feeling is terrific. It turns into two intermediate zones though, one high, and one lower. Two lenses in this category, The new Shamir InTouch and the new Seiko Supernal. Because they start the intermediate lower, its good for laptops, but the reading is little lower too. Fit on Center. I have to dig a little deeper in both lenses to get the fine print. Reading width is OK though]
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