Opticallimits

Full Version: Nikon's refractive phase Fresnel optics vs Canon's diffractive optics.
You're currently viewing a stripped down version of our content. View the full version with proper formatting.
We talked very briefly about Nikon's use of phase fresnel optics in the new AF-S 800mm F6.3 VR PF lens (and of course the 500mm F5.6 PF/300mm F4 PF lenses) ....... then BC mentioned the similar principles used in Canon's DO lenses ....... 
 While reading a thread on the aforesaid 800mm PF lens someone posted a link to the Lenstip review of the 300mm F4 VR PF lens where they pointed out the differences between Nikon's refractive optics and Canon's diffractive designs ...... 
  Clearly they are different approaches to a similar end result ..... 

Lenstip goes some of the way to an explanation here:

https://www.lenstip.com/index.html?test=...est_ob=431

 .. has anyone an understanding of these two principles ........ BC ... Klaus.... Marcus ??
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
They are wrong, Dave.

Both Canon and Nikon use diffraction, Canon in what they call "DO" (diffractive optics) and Nikon in what they call "PF" (Phase Fresnel) lens.

A Fresnel lens refracts light, in the same way "normal" refractive lenses work (they "bend" light). They just use less material, saving on weight and thickness.
https://nl.wikipedia.org/wiki/Fresnellens

The DO and PF elements rely on... diffraction, light "curving" around edges, breaking up light waves and recombining them into different waves.

I know that lenstip and other sources (like here https://www.whatdigitalcamera.com/techno...work-65045) keep saying that Nikon does not use diffractive optics... But they do.

Lets take Nikon's word for it:
"The PF (Phase Fresnel) lens, developed by Nikon, effectively compensates chromatic aberration utilizing the photo diffraction phenomenon*. It provides superior chromatic aberration compensation performance when combined with a normal glass lens. Compared to many general camera lenses that employ an optical system using the photorefractive phenomenon, a remarkably compact and lightweight body can be attained with less number of lens elements.

* Diffraction phenomenon: Light has characteristics as a waveform. When a waveform faces an obstacle, it attempts to go around and behind it, and this characteristic is referred to as diffraction. Diffraction causes chromatic dispersion in the reverse order of refraction."

The difference between what Canon makes and what Nikon uses is that Canon has found that combining two of these concentric circle patterns reduces/eliminates the flare that PF can cause around bright lights.

Nikon has used PF in microscope optics before they introduced it in their Nikkors.
https://www.nikon.com/news/2012/0925_cfi60_2_01.htm
"Phase Fresnel lens
This is a type of diffractive optical element.
Typically, a lens forms an image on, for example, a viewing plane or imaging plane, using the photorefractive phenomenon. The degree of light refraction differs depending on the color (wavelength), and image formation is performed in the order of blue (B), green (G), then red ® starting with the portion near the lens. The color deviation referred to as chromatic aberration induces color bleeding, resulting in a deterioration of observed or captured images.
To prevent this chromatic aberration, various methods are used such as combining a convex lens and concave lens or using lens glass materials with small chromatic aberration.

The phase Fresnel lenses developed by Nikon, on the other hand, uses the photo diffraction phenomenon.
Unlike the conventional refractive phenomenon, image formation is performed in the order of red ®, green (G), then blue (B) starting with the portion near the lens. Combining a phase Fresnel lens like this with a conventional refractive lens makes it possible to offset color deviation and intensively compensate for chromatic aberration.

Diffraction phenomenon: Light has characteristics as a waveform. When a waveform faces an obstacle, it attempts to go around and behind it, and this characteristic is referred to as diffraction.
Diffraction causes chromatic dispersion in the reverse order of refraction."

So to recap:
A Fresnel lens is a refractive optical device, not diffractive.

Both Canon's DO elements and Nikon PF elements are diffractive optical devices, not refractive. They are loosely based  on Fresnel's theories, but they are not Fresnel lenses.
They both (Canon and Nikon) essentially do the same thing, Canon a bit more advanced.
(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 !!
(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...
(05-16-2022, 07:30 PM)Brightcolours Wrote: [ -> ]    
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...

Ok ....... well there's a lot more to it than finally "meets our eye in the form of an image" that's for sure !!  ......... 

thanks for that BC !!
(05-16-2022, 07:30 PM)Brightcolours Wrote: [ -> ]
(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...

A response from you like this was to be expected.

David asked for a simple explanation. I gave that. It is that simple. I never said they were fresnel lenses, read my reply again.
FWIW, I've just banned BC. His technical insights have always been great but his communication style is, unfortunately, over the edge.

Let's keep this a peaceful place. This is just about photography.

Thx