part 2 - 13 elements in 11 groups (1 FLD, 1 SLD and 3 aspherical lens elements)
Edition Number
C022
Sensor Sizes
Full Frame
Angle Of Views
94.5°
Number of Diaphragm Blades
9 (rounded diaphragm)
Minimum Aperture
F22
Minimum Focusing Distance
22cm / 8.7 in.
Maximum Magnification Ratio
1:6.7
Filter Size
62mm
Dimensions
L-Mount: 70mm x 72.4mm / 2.8 in. x 2.9 in. Sony E-mount: 70mm x 74.4mm / 2.8 in. x 2.9 in.
Weight
"Premium Compact Primes" for mirrorless users
The Sigma I series features full-frame compatible lenses that offer new value to mirrorless systems. The combination of superb optical performance with a level of compactness that is perfectly suited to smaller and lighter modern mirrorless cameras will bring you new opportunities for a perfect shot. Sigma is aware that in today's world we have a wide range of camera choices, especially with the increase in mobile phone ownership. But with many people look for something more than a mere act of "taking pictures" when they choose to own a camera and lenses, I series lenses offer the ultimate combination of superb optical performance, outstanding usability and compact form-factor. Sigma's excellence in development and production technologies has been built up since our founding in 1961 and became increasingly sophisticated with the introduction of the Sigma Global Vision brand in 2012. With this as a base, Sigma has given careful thought to the quality of the products, the feeling of using it and the pleasure of owning it. This is how the I series was born. https://youtu.be/CWtkGaAhivI
New standards of optical performance for the Contemporary line
The 20mm F2 DG DN | Contemporary achieves the highest level of optical performance even at the widest aperture setting of F2 from the center of the image to the periphery. Based on the latest optical design technology, the lens construction includes three high-precision glass-molded aspherical lens elements, one SLD element, and one FLD element to suppress a range of optical aberrations. The result is clear and sharp images even in the extreme corners of the frame. By focusing on the suppression of sagittal coma flare, which is difficult to correct in post-processing, accurate reproduction of very bright points of light has been achieved. This also provides extremely detailed results across the entire image, which is especially important for night sky photography. The lens' optical design, as well as its Super Multi-Layer Coating and Nano Porous Coating (NPC), ensures very minimal flare and ghosting even when shooting into bright light sources. This makes it much easier to photograph backlit subjects and still achieve punchy, high contrast results.
Lens Construction
FLD glass
SLD glass
Aspherical lens
MTF CHART
The MTF (Modulation Transfer Function) is one of the measurements for evaluating a lens' performance, and it shows how faithfully the contrast of the subject can be reproduced on the image plane. The horizontal axis shows the image height (distance from the center of the image in mm) and the vertical axis shows the contrast value (maximum value is 1). The closer the 10 line pairs/mm curve is to 1, the higher the contrast and clarity of the lens is, and similarly, the closer the 30 line pairs/mm curve is to 1, the better the resolution and sharpness of the lens is. *The MTF chart depicts the result at the wide-open aperture. *For mirrorless lenses that support distortion correction, the horizontal axis shows the image height equivalent to when an L-Mount lens is attached to a Sigma L-Mount camera with distortion correction applied. (The effect of distortion correction may differ depending on the mount and camera used.) *The spatial frequency indicates the variation on the image plane before distortion correction is performed.
Spatial Frequency
S: Sagittal Line
M: Meridional Line
10lp/mm
30lp/mm
GEOMETRICAL MTF
DIFFRACTION MTF
Inner focus system
To increase stability, this lens configuration uses movable internal lens elements that adjust focus without changing the length of the lens barrel.
