And yet another Canon patent application: two telephoto fast primes for the RF mount.
Canon patent application 2023104022 (Japan, published 7/28/2023) discusses optical formulas for two fast telephoto prime lenses for the RF mount: RF 300mm f/2.8 IS and RF 400mm f/2.8 IS.
From the patent literature:
Optical System and Imaging Device Having the Same
Description of the Related Art
An optical system used in an imaging apparatus is required to be compact and lightweight as a whole, and to have high optical performance capable of satisfactorily correcting various aberrations including chromatic aberration. As a compact optical system, a so-called telephoto type optical system is known in which a lens group with positive refractive power is arranged on the object side and a lens group with negative refractive power is arranged on the image side. However, in the telephoto type optical system, the longer the focal length, the larger the entire system, and the use of a lens with a large diameter or a heavy lens tends to increase the weight of the entire optical system.
A new Canon patent for telephoto lenses with built-in teleconverter. For what mount? RF mount.
Canon patent 2022142979 (Japan, published 10/3/2022) discusses optical formulas for three telephoto lenses with built-in teleconverter. The lenses are 300mm f/2.8, 400mm f/2.8 and 600mm f/2.8. From the patent literature (machine translated):
An object of the present invention is to provide an optical system having a variable power optical system that is inserted into and removed from a main optical system, and to achieve good optical performance while reducing the weight of the entire system.
Description of the Related Art
As a method for changing the focal length of an optical system used in an imaging apparatus, there is a converter method that changes the focal length of the entire system by inserting a variable magnification optical system (extender) in the optical path.
When adopting a system incorporating a variable magnification optical system, in order to achieve good optical performance while reducing the weight of the entire system including the variable magnification optical system, the insertion position of the variable magnification optical system must be appropriately selected. It is important not only to do so, but also to properly configure the main optical system. The invention disclosed in Patent Document 1 has room for improvement from the viewpoint of achieving both weight reduction and optical performance.
Summary of the invention
It is an object of the present invention to achieve good optical performance while reducing the weight of the entire system in an optical system having a variable magnification optical system that is inserted into and removed from a main optical system.
Remember the Dragonfly Telephoto Array? Once more, commercial Canon telephoto lenses are used to build an array to observe and study galaxies and other astronomical objects.
The Canon lenses used to build the new array are the Canon EF 400mm f/2.8 L IS II. The new array, named Huntsman Telescope, is made by Macquarie Unversity with support from Canon, as Australian Photography reports:
Located at the Siding Spring Observatory near Coonabarabran, NSW, the Huntsman will perform deep southern sky surveys to provide researchers with understanding about galaxy formation and evolution; how galaxies form, how they grow, how they engage with structures that surround them, and what happens when galaxies collide.
Canon says the second-generation Canon EF 400mm f/2.8 L lens was chosen for the task as it has ‘superb’ anti-reflection properties, owing to one of the first applications of Canon’s nano-fabricated coatings. Each lens is connected to a red-coloured camera which is then individually connected to one of 10 mini computers.
The coated lens array chosen for the Huntsman contrasts to a conventional mirror telescope, whose imperfectly polished surface can introduce subtle errors that ruin faint, extended structures surrounding galaxies.
A new Canon patent application was spotted. 400mm f/4 DO IS Extender 1.4x and 600mm f/4 IS Extender 1.4x are discussed.
Canon patent application 2022-22771 discusses optical formulas for two rather interesting lenses:
400mm f/4 DO IS Extender 1.4x
600mm f/4 IS Extender 1.4x
PROBLEM TO BE SOLVED: To provide an optical system in which a magnification conversion optical group can be inserted and removed and the total length is short.
As a method of changing the focal length of the optical system used for imaging, there is a method of inserting a magnification conversion optical group such as an extender into the optical path . Further, as an optical system in which the total length (distance from the optical surface on the object side to the image surface) does not change due to the insertion / removal of the magnification conversion optical group, Patent Document 1 describes the axial light beam between the aperture stop and the image surface. An optical system capable of inserting and removing a magnification conversion group at a converging position is disclosed.
However, if a space for inserting the magnification conversion optical group is provided between the aperture diaphragm and the image plane as in Patent Document 1, the total length of the original optical system becomes long . Further, if the magnification conversion optical group is inserted in a narrow space, various aberrations of the optical system may increase. The present invention provides an optical system in which a magnification conversion optical group can be inserted and removed, but the total length is short and good optical performance can be obtained.
Example 1
Focal length: 392.58
F value: 4.12
Half angle of view: 3.15
Image height: 21.64
Overall length: 280.33
Back focus: 36.01
Example 1 (with inserted teleconverter)
Focal length: 549.72
F value: 5.77
Half angle of view: 2.25
Image height: 21.64
Overall length: 280.33
Back focus: 36.00
Example 5
Focal length: 585.00
F value: 4.12
Half angle of view: 2.12
Image height: 21.64
Overall length: 467.45
Back focus: 55.50
Example 5 (with inserted teleconverter)
Focal length: 819.18
F value: 5.77
Half angle of view: 1.51
Image height: 21.64
Overall length: 467.45
Back focus: 55.50
The Canon patent application was spotted by asobinet.com. More Canon patent applications are listed here. Some particularly interesting patent applications we think might get into production are these:
We reported about the Dragonfly Telephoto Array in the past. It’s a project developed by the University of Toronto’s Dunlap Institute for Astronomy and Astrophysics for which Canon delivers the optics.
The Dragonfly Telephoto Array started with 10 lenses and is designed to reveal
[…] the faint structure [of the universe] by greatly reducing scattered light and internal reflections within its optics. It achieves this using ten, commercially available Canon 400mm lenses with unprecedented nano-fabricated coatings with sub-wavelength structure on optical glasses.
Now Canon provides 120 (one-hundert-twenty) more EF 400mm f/2.8L IS II lenses to the array. So, now that you got what it is about, here is a more detailed description about the Dragonfly Telephoto Array:
The Dragonfly Telephoto Array is a novel telescope concept designed to image large and extremely faint structures in the night sky. These structures hold important clues to the distribution and nature of dark matter, the elusive substance whose contribution to the total mass-energy density of the Universe is five times higher than that of normal matter. These structure are hard to see with conventional telescopes due to a combination of scattered light from bright stars and their mosaicked detectors. Dragonfly harnesses the power of commercially-available high-end telephoto lenses to address these issues. The latest generation of Canon 400 mm f/2,8 lenses have superb anti-reflection properties, owing to one of the first applications of nano-fabricated coatings with sub-wavelength structures on optical glasses. Furthermore, each lens is equipped with a single monolithic wide-field detector covering six square degrees, and with multiple redundant lines of sight Dragonfly achieves extremely accurate modeling of the night sky emission.
Commissioned in 2013 with three lenses, the array currently consists of 48 lenses in two clusters of 24. Optically the telescope functions as the equivalent of a 1.0 m diameter refractor with a focal ratio of f/0.4, the largest and by far the most sensitive lens telescope in existence. “Behind the scenes” innovations include the use of AI planning tools to optimize nightly operations and survey design, unit-based basic data processing with compute sticks, the application of Internet of Things operational protocols to communicate with the 48 lenses, and fully automated gate-driven cloud-based data analysis. Our dual goals are to:
1. Improve our understanding of dark matter through study of the low surface brightness universe
2. Harness the potential of distributed telescopes, combined with advances in information technology, for transformational science
Canon U.S.A. Inc., to Provide 120 EF 400mm f/2.8L IS II USM Lenses for Expansion of the Dragonfly Telephoto Array Project
MELVILLE, NY, November 18, 2021 – Canon U.S.A. Inc., a leader in digital imaging solutions, today announced the company will provide technical assistance to Project Dragonfly, an international research team from Yale University, and the University of Toronto, in its plan to expand the Dragonfly Telephoto Array. The company will provide the project with 120 Canon EF 400mm f/2.8L IS II USM large-aperture super-telephoto single-focal length lenses, and its parent company, Canon Inc., will provide technical assistance.
The Dragonfly Telephoto Array is a telescope array equipped with multiple Canon large-aperture super-telephoto single focal length lenses – specifically, the Canon EF 400mm f/2.8L IS II USM lens. The telescope was designed in 2013 by Project Dragonfly, an international research team from Yale University and the University of Toronto. The Dragonfly Telephoto Array is capable of capturing images of galaxies that are so faint and large that they had escaped detection by even the largest conventional telescopes. Its mission is to study the low surface brightness universe to elucidate the nature of dark matter and to utilize the concept of distributed telescopes.
In support of this research, Canon provided technical assistance by supplying 40 Canon EF 400mm f/2.8L IS II USM lenses in 2015, expanding the array to 48 lenses with 24 telescopes bundled on two separate mounts. Since then, the research team has produced significant results in extragalactic astronomy, including discovering the ultra-diffuse galaxy Dragonfly 44 in 2016 and the identification of a galaxy that lacks dark matter, NGC 1052-DF2, in 2018.
This time, Canon will provide technical assistance by supplying 120 Canon EF 400mm f/2.8L IS II USM lenses to the research team, further expanding the telescope array. With a total of 168 lenses, the telescope array has a light-gathering capability equivalent to that of a refracting telescope of 1.8 meters in diameter, with a focal length of only 40 cm, and is expected to open new windows on the universe.
Canon is committed to contributing to the development of science and technology by leveraging the technological strengths it has cultivated as a leading imaging company.
Message from Professor Pieter van Dokkum of Yale University comments
The Dragonfly Telephoto Array is the pre-eminent survey telescope for finding faint, diffuse objects in the night sky. It has enabled us to discover ultra-diffuse galaxies and other low-surface brightness phenomena—rendering images that deepen our understanding of how galaxies are formed and providing key insights into the nature of dark matter. The initial array was equipped with 48 Canon EF 400mm telephoto lenses featuring anti-reflection coatings that mitigate the effects of light scattering, overcoming the limitations of conventional telescopes in detecting faint structures. The lenses are coupled to monolithic wide-field detectors that permit excellent error control. With the addition of 120 of these lenses, in a newly developed configuration allowing extremely narrow filters to be used, Dragonfly will be the most powerful wide-field spectroscopic line mapping machine in existence. A major goal of the next iteration of the Dragonfly array is to detect and study the faint gas thought to exist around and between galaxies. By opening this new window on the cosmos, Dragonfly will tackle some of the most critical questions in astrophysics today.
So, we are talking about a $12,000 lens here. Welcome to a new Canon RF 400mm f/2.8L IS review. How doesn’t have a spare kidney?
At a glance:
RF-Mount Lens/Full-Frame Format
Aperture Range: f/2.8 to f/32
Optical Image Stabilizer
Super UD and Fluorite Elements
Super Spectra and Air Sphere Coatings
Customizable Electronic Focusing Ring
Two Focus Presets
Circular 9-Blade Diaphragm
Weather-Sealed Design, Fluorine Coating
Rotatable Tripod Collar
Christopher Frost posted his Canon RF 400mm f/2.8L IS review. He says:
This is literally the highest quality camera lens I have ever handled – physically awesome, optically impeccable…and incredibly expensive. Canon have been honing the craft of designing and producing these lenses for years, now: what can this latest version achieve to make it worth its asking price?
Watch the video below to learn what makes this lens so awesome, and so expensive.
Another rather interesting Canon RF 400mm f/2.8L IS review can be seen here.
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