Canon Patent: Underwater Attachment Optic For Better Performance

Canon Patent

Very interesting Canon patent application. If I got it right, it is for a sort of underwater attachment optic you can mount on a telephoto lens. The optical system should deliver an optical underwater performance that’s close to what you get when using the lens on the surface (i.e. in “air”).

Canon patent application 2022-24363 (Japan) discusses technology and optical formulas for an optical filter system that gets mounted on a lens and should deliver much better optical performance under water.

PROBLEM TO BE SOLVED: To provide an attachment optical system capable of obtaining optical performance close to that in the case of use in air when used in water with a simple configuration.

Conventionally, an attachment optical system for mounting on an image pickup lens is known. In recent years, the number of users who enjoy shooting underwater is increasing, and the demand for an image pickup lens optimally designed for underwater use is increasing. Generally, as an underwater camera or an amphibious camera, a camera in which the camera is housed in an underwater housing or a camera in which the camera itself is provided with a waterproof mechanism is used. However, the refractive index and dispersion of water and salt water are different from those in air. For example, the refractive index for the d-line is about 4/3 with respect to air, and the dispersion is about 62 in Abbe number. Therefore, when an image pickup optical system whose aberration is sufficiently corrected in air is used in water, the refraction action at the interface between water and the image pickup optical system changes, and the optical performance deteriorates due to the change in aberration.

When an optical system that has been subjected to aberration correction on the assumption that it is used in air is used in water, the aberration changes as described above. Specifically, it is necessary to extend the focus lens group in order to generate curvature of field on the over side, distortion, and to shift the focus position to the rear of the image plane and return the focus to the image plane position. There is the occurrence of aberration fluctuation due to. Further, the change in aberration becomes more remarkable as the thickness of the housing mounted in front of the optical system becomes thicker when used underwater. With the attachment optical system disclosed in Patent Document 1 and Patent Document 2, it is difficult to cope with all of the above-mentioned changes in aberration, and the optical performance when used in water is close to that when used in air. Cannot be obtained.

Therefore, the present invention presents an attachment optical system, an optical system, and a method for manufacturing an optical system, which can obtain optical performance close to that of use in air when used in water with a simple configuration. The purpose is to provide.

The attachment optical system as one aspect of the present invention has a first converter optical system that can be attached to the object side of the image pickup optical system, and the first converter optical system has a dome-shaped cover. It has one unit and a second unit composed of a plurality of lenses, and the second unit has a negative refractive power arranged at a position closest to the first unit in the second unit. The focal length fd of the first unit, the focal length ffc of the second unit, and the focal length fn of the lens having a negative refractive power in the second unit in water having a lens are predetermined conditional expressions. To be satisfied. suggests this is for movie application and less for stills photography. They also suggest it is for a zoom lens for the Canon EOS Cinema system.

Canon EOS R5 Review For Underwater Photo And Video

Canon EOS R5 Review

Canon set a new reference standard with the Canon EOS R5, overheating drama included. Here is a Canon EOS R5 review for underwater photography and video.

Coming from the folks at Bluewater Photo Store, the video below is…

[…] a full review of the Canon EOS R5 full frame, 45 megapixel mirrorless camera for underwater photo and video. The R5 has some of the best specs on the market including 45 MP still images, 8K video @ 30P with internal RAW recording, 4K video up to 120fps, 5 axis in-body image-stabilization, and more!

The staff at Bluewater Photo and the Underwater Photography Guide took the Canon EOS R5 diving in the cold waters of the Puget Sound, Washington to put it to the test and see just what it could do. We’ve been very impressed with the underwater footage that we captured. However, we do think that the marketing by Canon for the R5 should have been done differently – this is a spectacular still camera with amazing video features, but it should not be relied on for the video features that were initially marketed.

Well, at least underwater the heating issue should be under control ;-)

The EOS R5 seems to be highly regarded as a stills camera. In particular, the EOS R5 autofocus system seems to be huge leap forwards. More Canon EOS R5 review stuff is listed here, for the EOS R6 see here. User manual are available for download for the EOS R5 and the EOS R6. My opinion about the EOS R5 overheating hysteria is listed here.

Canon EOS R5 body and kits preorder links:

America: B&H Photo, Adorama, Amazon USA, Amazon Canada, Canon Canada, Canon USA
Europe & UK: Amazon DE, Amazon UK, Amazon IT, Canon IT, WEX Photographic, Canon FR, Canon UK, Canon DE

Click here to open the rest of the article

Sea & Sea Announce Canon EOS 5D Mark IV underwater housing

Eos 5d Mark Iv

At a glance:

  • Construction: Corrosion-resistant aluminum alloy (machined, anodized finish)
  • Grip: Corrosion-resistant die-cast aluminum alloy
  • Depth Rating: 100m/330ft
  • Dimensions (WxHxD): 341 x 198 x 141mm /13.4 x 7.8 x 5.5 inches
  • Weight (Approx.): 3,000g/106oz (Housing only)

Sea & Sea announced an underwater housing for the Canon EOS 5D Mark IV. The housing fits also an EOS 5D Mark III, EOS 5Ds and EOS 5Ds R. Reccomended price is $3,899.95, shipping to start soon.

Press release (via Dive Photo Guide):

U/W Housing for Canon EOS 5D Mark IV / EOS 5D Mark III
Housing satisfies even professional needs with its superior ergonomic design and ruggedness

MDX-5D Mark lV housing (black) (housing only) (Product No.06181)

Relevant Information

The MDX-5D Mark lll and the MDX-5D Mark lll ver. 2 housings can be converted to accommodate both the EOS 5D Mark lV and the EOS 5D Mark lll (fees apply).


  • Important controls can be operated whilst holding the grips. Frequently-used buttons such as ISO, AF Point Selection and Multi-function Selection buttons are operated by external levers, allowing quick and accurate operation.
  • The main command dial, the quick control dial and others have a damper (spring) to provide secure operation. (Controls on the camera will not slip because of the damper).
  • The tension on the Shutter Release lever can be adjusted in 3 steps
  • Compatible with Optical YS Converter/C.
  • Tripod screw mount is located on the centre underside of the housing.
  • Built-in leak sensor immediately alerts you to water ingress.
  • Equipped with two sacrificial zinc diodes (one on the front case and the other on the rear) to prevent electrolysis damage.
  • Accessory port enables use of Leak Sentinel (vacuum sensor).
  • Sync Cord 2-pin Connector enables use of conventional hardwired Sync cable (Manual mode only).
  • Equipped with the Optical Viewfinder 0.5x as standard. Other optional viewfinders such as the VF180 1.2x, VF45 1.2x and Optical Viewfinder 0.8x can be used.
  • All controls have luminescence stickers which glow in dark environment.
  • Pulling out the Focus/Zoom Dial gives sufficient room inside the housing to easily accommodate larger diameter lenses.
  • The camera’s diopter adjustment dial can be operated from outside the housing. This feature is useful when two or more people with different eyesight use the housing.
  • The housing is equipped with a lens-lock release button which makes it possible to change lenses easily, without opening the housing.
  • The Port Lock prevents the port from turning or loosening and the Port Lock lever is specifically located to avoid being unlocked accidentally.

eos 5d mark iv