Sigma 20mm F1 8 EX DG ASP RF Review | 54 Data compared

The Sigma AF 20mm f/1.8 EX DG RF lens delivers a mix of impressive highlights and notable drawbacks when tested on a DX format camera. On the positive side, the lens boasts very solid build quality with no wobbling parts, unlike its sister lenses. It produces very good to excellent sharpness in the center of the frame even wide open, and chromatic aberrations are kept well under control. Additionally, its exceptionally short minimum focus distance makes it a highly capable and unique tool for wide-perspective close-up photography. However, the lens suffers from several optical and mechanical limitations that hurt its overall appeal for DX shooters. The corner and border resolution is poor at wide apertures, only recovering to very good levels once stopped down to f/5.6. Vignetting is highly pronounced at f/1.8, and the lens introduces a fair amount of barrel distortion that surprisingly worsens on crop-sensor bodies. Furthermore, the bokeh rendering is nervous with noticeable outlining and fringing at large apertures. Finally, a lack of an internal autofocus motor means this lens will not autofocus on entry-level Nikon DX...

The Sigma 20mm f/1.8 EX DG is an ultra-wide prime lens offering decent contrast, pleasing color, and smooth background blur via a 9-blade aperture. While it boasts accurate internal focusing and slightly brighter exposure capability, users must manage significant wide-open softness, heavy vignetting, and prominent chromatic aberration. The-Digital-Picture.com Drawbacks include high flare susceptibility, a loud autofocus motor, and a "Dual-Focus" clutch mechanism that is prone to accidental adjustment. Despite these mechanical and optical flaws, the lens provides a unique, fast aperture option for full-frame cameras when stopped down, according to the review at The-Digital-Picture.com.

The Sigma 20mm f/1.8 EX DG is a highly unique, budget-friendly wide-angle lens ($460) praised primarily for its exceptional brightness, making it a compelling tool for night and Milky Way photography. On the positive side, the lens features good build quality, perfect colour reproduction without casts, and a very large focus ring ideal for fine-tuning manual focus. Its physical footprint is also surprisingly compact and lightweight given its fast f/1.8 aperture. Center sharpness is acceptable, and autofocus speeds are decent, providing a functional experience for users who require an ultra-wide, low-light lens without paying for premium alternatives. However, the reviewer highlights severe optical drawbacks and explicitly advises against purchasing the lens for general use. The overall image quality is poor due to extreme corner softness caused by a curved plane of focus, making the corners look out of focus even when stopped down to f/5.6 or f/8. Additionally, the lens suffers from low corner contrast, strong vignetting wide open, barrel distortion, coma, and a heavy tendency to flare near bright light sources. Mechanically, it lacks an HSM motor, lacks full-time...

This unique wide-angle prime lens stands out as the only 20mm option on the market offering a very wide maximum aperture of f/1.8, making it an intriguing and affordable choice for low-light situations like weddings or DSLR video shooting. Its robust build quality ensures it feels solid and well-balanced on cameras like the Canon EOS 60D, while its remarkably close focusing distance of 2.6 inches allows photographers to easily isolate subjects and create smooth background bokeh. Additionally, when the lens is stopped down to f/2.8 or f/3.5, it delivers sharp images and accurate, fast autofocusing in well-lit environments. However, the lens is defined by significant contradictions, most notably that its images are quite soft and unimpressive when shot wide open at f/1.8—the exact feature meant to be its main selling point. In low-light conditions, the autofocus tends to search, and the motor produces a noticeable amount of noise. Users will also have to deal with heavy vignetting around the corners at wide apertures, poor management of lens flare from strong light sources, and the added expense of purchasing large 82mm...

This review by Markus Stamm on OpticalLimits evaluates the Sigma AF 20mm f/1.8 EX DG RF wide-angle lens using a full-format Nikon D3x test camera. Belonging to Sigma’s high-end "EX" line, the lens features a sturdy build quality characterized by a rear-focus design. This ensures the physical length remains constant and prevents internal tube wobbling. Optically, the lens delivers mixed results; it provides very good to excellent center resolution, but the borders and corners disappoint at wide apertures. It is also prone to pronounced wide-open vignetting and typical fast-prime bokeh fringing. The lens offers key functional advantages, such as an exceptionally short minimum focus distance of 0.2 meters for dramatic close-up perspectives and a non-rotating front element that allows for easy polarizer use. It features a broad clutch-style focus ring that allows full-time manual focusing (FTM). However, the focus ring rotates in "Canon" style, which is the exact opposite of native Nikkor lenses, presenting a challenge for Nikon users' muscle memory and causing the viewfinder's focus assist to suggest the wrong direction. Additionally, because it lacks a built-in AF motor,...