Very interesting Canon patent application: a set of RF mount lenses with electronically controlled Defocus Smoothing (DS).

Defocus Smoothing is a technology Canon first introduced with the RF 85mm f/1.2L DS lens (see here for our coverage). The featured Canon patent might suggest more DS lenses are on their way.

Canon patent application 2020-199390 (Japan) discusses optical formulas and methods for three prime lenses with DS:

• 135mm f/2
• 400mm f/4
• 50mm f/2.5

From the patent literature:

PROBLEM TO BE SOLVED: To provide an optical device capable of sufficiently adjusting the clarity of the outline of a blur even if the aperture diameter of a diaphragm is greatly changed.

BACKGROUND ART: Conventionally, an image formed by an optical device may be required to include a blur with a smooth outline, or may include a blur with a clear outline. May be required.

Patent Document 1 discloses an optical device capable of smoothing or clarifying the outline of blur by providing an optical element capable of reversibly switching the distribution of transmittance. The clarity of the outline of the blur is required to be sufficiently adjustable even when the aperture diameter of the diaphragm is greatly changed.

However, the optical device disclosed in Patent Document 1 is insufficient to meet the above-mentioned requirements because the clarity of the outline of the blur can be sufficiently adjusted only in the vicinity of the opening of the aperture.
Therefore, an object of the present invention is to provide an optical device capable of sufficiently adjusting the clarity of the outline of a blur even if the aperture diameter of the diaphragm is greatly changed. In various optical systems such as photographic and video lenses, not only the characteristics of the image plane but also the image quality of the out-of-focus portion, that is, the quality of blur may be emphasized.

In general, there are cases where a smooth blur that melts without a clear outline is desired, and there are cases where a blur with a clear outline is desired. As a method of changing the contour of the blur, for example, a method of inserting an apodization filter whose transmittance decreases as the distance from the optical axis increases is known.

As a result, the transmittance distribution of the apodization filter is superimposed on the blurred image, and smooth blurring such that the contour melts can be realized. However, when the apodization filter is inserted, the outline of the blur is always smooth in the vicinity of the opening of the aperture, so that it becomes difficult to clarify the outline of the blur according to the request.

Further, when the apodization filter is inserted, the amount of transmitted light in the optical system is reduced, so that the demerit of inserting the apodization filter becomes greater in the shooting scene where almost no blurring occurs in the screen.
Therefore, there is also known a method of switching the apodization effect on and off by using an optical element capable of reversibly controlling the distribution of the transmittance, that is, adjusting the clarity of the outline of the blur according to a request.

Example 1

• Focal length: 133.05
• F value: 2.06
• Half angle of view: 9.24
• Image height: 21.64
• Overall length: 170.39
• Back focus: 45.96

Example 2

• Focal length: 399.84
• F value: 4.00
• Half angle of view: 3.10
• Image height: 21.64
• Overall length: 298.46
• Back focus: 145.16

Example 3

• Focal length: 49.00
• F value: 2.50
• Half angle of view: 23.82
• Image height: 21.64
• Overall length: 68.15
• Back focus: 11.00

The following, short video tells what Defocus Smoothing is:

[via asobinet]