NikonGear'23
Gear Talk => Lens Talk => Topic started by: chambeshi on June 24, 2021, 19:24:44
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Scrolling down to the Figs outlines 4 different designs; each including a diffraction element. Each design reduces the total length of the zoom to different respective length(s). Both versions of a 200-500 f5.6 are variable length and rather long TL
It appears first and second examples are versions of a 200-500 f5.6 of variable length and rather long TL.
The Third Example invoking a ~300-600 f6.4 reduces TL of the lens into a fixed length zoom of approx 94 x 330mm (600 f4E FL is 160 x 432mm, 3.8kg). The 4th example of a 400-800 f8 is also of fixed length at approx 100 x 435mm (800 f5.6E FL is 160 x 461mm and 4.59kg).
The window further suggests 95-100mm is the maximum to mass produce a high quality phase-fresnel element efficiently. The 500 f5.6 PF takes 95mm filters
WO2021124804 on https://www.wipo.int/portal/en/index.html