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Nikon's refractive phase Fresnel optics vs Canon's diffractive optics.
(05-16-2022, 05:13 PM)davidmanze Wrote:
(05-16-2022, 03:59 PM)wim Wrote: The principle of DO at its simplest is cutting up the optics in perfectly circular rings, which are perfectly centered around the optical axis, removing the excess of glass for each ring, to just allow for the refraction required, and put everything together again, thus making a much flatter and lighter lens element possible.

In real life the construction is done without cutting up the lens element, often by using a synthetic material, like acrylic or something similar, and casting it. In order to avoid any dust gathering in the circles, it tends to be embedded in a matrix of another synthetic/plastic, with a different refractive index.

Rather complex, difficult to manufacture, and difficult to design due to different wavelengths having different refractive indices, which creates havoc, in principle, especially on or at the edges of each circular structure.

In a way, it is a fresnel lens, but not to create an evenly illuminated area, but to use as a real lens element.

HTH, kind regards, Wim

     Hi wim ......
   ...... well done! ..... you clearly have a good understanding of the principle and processes there ! ...... and it certainly doesn't sound like Canon was taking the easy route .......   
  to be honest I find the process a little unsettling ..... I think I'd wake up sweating in the middle of the night imagining my front DO element was shedding it's acrylic coating ..... Smile

do they have issues ??

thanks in advance .....

thanks !!
Except that Wim does not understand the principle if the DO/PF. They are not Fresnel lenses with refractive optical properties like "normal" lenses, but instead diffractive optical elements...

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RE: Nikon's refractive phase Fresnel optics vs Canon's diffractive optics. - by Brightcolours - 05-16-2022, 07:30 PM

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