Canon Patent: RF 18-35mm f/1.8 DS & RF 120-300mm f/2.8 DS (Defocus Smoothing)

Defocus Smoothing

And here is another Canon patent application for two RF-mount lenses with Defocus Smoothing technology.

Canon patent application 2022175307 (Japan, published 11/25/2022) discusses optical formulas for two RF-mount lenses with Defocus Smoothing technology, RF 18-35mm f/1.8 DS & RF 120-300mm f/2.8 DS. No surprise Canon is porting this technology to the RF-mount. From the patent literature:

To provide a variable power optical system that obtains a good apodization effect over the entire zoom range and that has a small change in T number with variable power.

Description of the Related Art

Conventionally, in order to obtain an appropriate blurred image, there has been known an optical system equipped with a filter whose transmittance distribution changes, such as an apodization filter whose transmittance decreases as the distance from the optical axis increases. ing. Patent Literature 1 discloses an optical system in which apodization filters are arranged before and after the aperture of a single-focus lens.

However, since the optical system disclosed in Patent Document 1 is a single focus optical system, it is insufficient as a method for obtaining a sufficient apodization effect in each zoom state of the variable magnification optical system. In addition, as a specific requirement of a variable-magnification optical system, it is required that the change in brightness, that is, the T-number, is small when the magnification is varied, especially in video shooting.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide a variable magnification optical system and an optical apparatus which have a good apodization effect over the entire zoom range and have a small change in T-number due to variable magnification.

Example 1

  • Focal length: 18.60-33.78
  • F-value: 1.80-1.86
  • Half angle of view: 37.69-23.05
  • Image height: 14.37
  • Overall length: 168.50
  • Back focus: 38.56-39.91

Example 2

  • Focal length: 18.50-34.00
  • F-value: 1.75-1.86
  • Half angle of view: 37.99-23.03
  • Image height: 14.45
  • Total length: 163.25-166.00
  • Back focus: 38.56-41.75

Example 3

  • Focal length: 37.00-68.00
  • F-value: 1.65-1.86
  • Half angle of view: 25.94-14.83
  • Image height: 18.00
  • Total length: 326.49-332.00
  • Back focus: 77.12-83.49

Example 4

  • Focal length: 51.50-97.00
  • F-value: 1.87
  • Half angle of view: 15.59-8.43
  • Image height: 14.37
  • Total length: 204.13-204.12
  • Back focus: 48.80-48.79

Example 5

  • Focal length: 123.60-290.82
  • F-value: 2.89
  • Half angle of view: 9.93-4.25
  • Image height: 21.64
  • Total length: 433.07-433.08
  • Back focus: 54.98-55.00

Sigma 18-35mm F/1.8 Deal – $499 (reg. $799, limited time)

Sigma 18-35mm F/1.8 Deal Art DC ART

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Sigma 18-35mm F/1.8 deal key features:

  • Lens Mount: Canon EOS
  • Zoom Focal Length: 18-35mm Lens
  • Lens Format: APS-C / DX
  • Maximum Aperture: f/1.8
  • Lens Type: Wide Angle Zoom SLR Lens
  • Image Stabilization Type: No
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  • Special Features: Aspherical
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Sigma 18-35mm f/1.8 deal key features:

  • EF-Mount Lens/APS-C Format
  • 28.8-56mm (35mm Equivalent)
  • Aperture Range: f/1.8 to f/16
  • Five SLD Elements

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Only for today (3/1/2020) authorised Sigma retailer Adorama has an excellent Sigma 18-35mm f/1.8 deal.

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Sigma 18-35mm F/1.8 deal key features:

  • This Sigma 18-35mm F/1.8 Bundle comes with:. Plus Free Bonus items ( $59.00 Value) : Sigma USB Dock
  • This lens is part of Sigma’s Art line; deeming it well-suited to creative image making due to its large, constant f/1.8 maximum aperture and ability to produce aesthetic bokeh by way of a nine-blade circular diaphragm
  • One aspherical lens element, as well as the incorporation of SLD glass, help to minimize the appearance of distortions and aberrations throughout the zoom range and provide clear imagery with enhanced sharpness
  • The Hyper Sonic Motor provides fast, quiet and smooth auto focusing that is well-suited for use with video applications. This AF motor can also be manually overridden at any time by rotating the focusing ring, giving you the ability to fine-tune image sharpness through manual focusing
  • Constructed using a TSC compound material, this lens is lightweight while also exhibiting notable durability and resistance to environmental changes
  • An internal focusing and zooming mechanism helps to maintain a consistent overall lens length and a non-rotating front ring facilitates more efficient use of circular polarizers
  • Compatible with Sigma’s USB Dock and Sigma Optimization Pro software for fine-tuning your lens’ performance, updating its firmware and better suiting it to your needs
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More to check…


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  • EF-Mount Lens/APS-C Format
  • 28.8-56mm (35mm Equivalent)
  • Aperture Range: f/1.8 to f/16
  • Five SLD Elements
  • Four Aspherical Elements
  • Super Multi-Layer Coating
  • Hyper Sonic Motor AF System
  • Rounded 9-Blade Diaphragm

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