Some details of these Zoom-Tele PF patents
Well.... a 300-600 f6.3 PF on a capable Z MILC will be useful, very useful indeed
[EDITED Recent patent overview added for April 2024]
Overview of Z Lens patents, including these 3 PF Zooms and a 1000 f8 PF Prime
Nikon Z-mount lens patents suggest future lenses
www.zsystemuser.com
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 the Third Example invoking a ~300-600 f6.4 reduces TL of the lens the most in a fixed length zoom approx 94 x 330mm (600 f4E FL is 160 x 432mm weighing a breathtaking 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).
excerpts
[0002]
Conventionally, it is known that providing a diffractive surface in an optical system has an achromatic effect (see, for example, Patent Document 1). In particular, in a telephoto lens, by arranging the diffraction surface as far forward (object side) as possible in the lens group, a larger achromatic effect can be exhibited, which makes it possible to shorten the overall length and reduce the weight of the optical system. However, on the other hand, when strong light is incident on the diffractive surface from outside the imaging screen, the diffracted light may flare and reduce the contrast of the entire screen. Therefore, it is required that the diffraction surface be arranged at an appropriate position where the contrast decrease due to flare can be reduced while sufficiently exerting the achromatic effect.
[0086]
(Table 1) First Example
[Overall specifications]
Wide-angle end state Intermediate focal length state Telephoto end state
f = 205.000 to 300.000 to 400.000 to 486.800
FNO = 5.80 to 5.80 to 5.80 to 5.80
2ω (°) = 12.20 to 8.10 to 6.10 ~ 5.00
Ymax = 21.700 ~ 21.700 ~ 21.700 ~ 21.700
TL (length in air) = 309.985 ~ 346.860 ~ 371.010 ~ 386.088
Bf (air conversion length) = 46.220 to 46.220 ~ 46.220 to 46.220
[0099]
(Table 4) Second Example
[Overall specifications]
Wide-angle end state Intermediate focal length state Telephoto end state
f = 205.000 to 300.000 to 400.000 to 486.800
FNO = 5.80 to 5.80 to 5.80 to 5.80
2ω (°) = 12.20 to 8.10 to 6.10 ~ 5.00
Ymax = 21.700 ~ 21.700 ~ 21.700 ~ 21.700
TL (length in air) = 309.991 ~ 348.121 ~ 376.459 ~ 395.024
Bf (air conversion length) = 53.850 to 53.850 ~ 53.850 to 53.850
[0112]
(Table 7) Third Example
[Overall specifications]
Wide-angle end state Intermediate focal length state Telephoto end state
f = 306.000 to 375.000 to 450.000 to 588.000
FNO = 6.40 to 6.40 to 6.40 to 6.40
2ω (°) = 8.10 to 6.40 to 5.30 ~ 4.10
Ymax = 21.700 ~ 21.700 ~ 21.700 ~ 21.700
TL (length in air) = 329.948 ~ 329.948 ~ 329.948 ~ 329.948
Bf (air conversion length) = 52.139 to 52.139 ~ 52.139 to 52.139
[0125]
(Table 10) Fourth Example
[Overall specifications]
Wide-angle end state Intermediate focal length state Telephoto end state
f = 407.999 to 499.999 to 599.999 to 783.998
FNO = 8.10 to 8.10 to 8.10 to 8.10
2ω (°) = 6.10 to 5.00 ~ 4.10 ~ 3.10
Ymax = 21.700 ~ 21.700 ~ 21.700 ~ 21.700
TL (length in air) = 435.067 ~ 435.067 ~ 435.067 ~ 435.067
Bf (air conversion length) = 73.106 to 73.106 ~ 73.106 to 73.106