05-16-2022, 05:02 PM
(This post was last modified: 05-16-2022, 05:36 PM by Brightcolours.)
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.
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.