To compete with the Tamron 35-150mm F/2-2.8 Di III VXD lens, Sigma is now working on a 50-140mm lens with a constant aperture of f/2.8. It may have an affordable price tag and they are also working on a new generation of 70-200mm f/2.8 lens.
We, already have Sigma lenses like 50-100mm F1.8, Sigma has filed a patent for a 50-140mm F1.8 Lens. In General whenever a camera maker files a patent for a new product, it roughly they take 1-2 years to make it an official. We do believe Sigma will put extra effort to make it faster.
Patent Details
[Publication number] P2023090116
[Release date] 2023-06-29
[Title of Invention] Imaging Optical System
[Application date] 2021-12-17
[Applicant]
[Identification number] 000131326
[Name] Sigma Corporation
Example 1
- Focal length: 50.50-136.50
- F-value: 2.92
- Half angle of view: 30.62-11.40
- Image height: 14.20
- Total length: 125.00-145.00
Kind Code: A1 A compact image forming optical system having a small open F value over the entire zoom range is provided.
2. Description of the Related Art
In recent years, a so-called mirrorless camera, which eliminates a quick-return mirror that is arranged between an imaging optical system and an imaging device and guides light rays to a finder optical system, has become popular. Since the body of the mirrorless camera has been downsized by eliminating the mirror, downsizing of the imaging optical system is required accordingly. Also, there is a demand for a large aperture zoom lens with a small open F-number over the entire zoom range.
[0004]
Patent Document 1 discloses a positive lead type zoom lens having a bright open F number of about 2.8 and having a lens group closest to the object side fixed with respect to an image plane during zooming. Since the optical total length does not change, convenience and robustness are high, but there is a problem that the size of the imaging optical system is large. Patent Document 2 discloses a positive lead type zoom lens having a bright open F number of about 2.8 and a shortened total optical length at the wide-angle end. However, since many lens groups with large diameters that move during zooming are arranged on the image side of the aperture stop, the mechanism required for zooming is large, and the size of the lens barrel in the radial direction is large. .
SUMMARY OF THE INVENTION It is an object of the present invention to provide a compact image forming optical system with a small open F value over the entire zoom range .
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