The Sigma 17–40mm F1.8 DC | Art lens marks a bold step forward in zoom lens engineering for APS-C mirrorless systems. Designed as the spiritual and technical successor to Sigma’s widely acclaimed 18–35mm F1.8 DC HSM | Art, this new lens pushes the boundaries of what’s possible in a compact zoom. It retains the hallmark constant F1.8 aperture throughout the entire focal range while expanding the zoom span from 17mm at the wide end to 40mm at the telephoto end. This extended reach opens up new creative possibilities for both still photographers and videographers, particularly those who want prime-level image quality with the versatility of a zoom.
At its core, the 17-40mm F1.8 DC | Art lens is built for uncompromising optical performance. It incorporates a sophisticated optical formula consisting of 17 elements in 11 groups, including four Special Low Dispersion (SLD) elements and four aspherical lenses. This advanced construction helps reduce chromatic aberration, distortion, and other image-degrading artifacts across the entire zoom range. The result is stunning image sharpness, impressive edge-to-edge clarity, and minimal color fringing-even when shooting wide open at F1.8.
Sigma has managed to deliver this exceptional image quality in a lighter, more compact form factor. The lens weighs just 535g (18.9 oz) in its L-Mount version, which is over 30% lighter than the previous 18–35mm model. It also features a narrower barrel diameter with a 67mm filter thread, making it more portable and convenient for field use. Despite these reductions, the lens still boasts a solid and durable feel with a professional-grade build, an internal zoom mechanism to protect against dust and moisture, and the sleek design language typical of the Art series.
This lens is built with video production in mind as much as still photography. The inner zoom design helps maintain consistent balance when mounted on gimbals or sliders, while the High-response Linear Actuator (HLA) autofocus motor delivers fast, accurate, and silent focus transitions ideal for recording video. Minimal focus breathing and smooth aperture changes contribute further to a seamless shooting experience. Whether used for astrophotography, documentary filmmaking, or landscape videography, the lens provides stability and optical fidelity in dynamic conditions.
The constant F1.8 aperture is one of the standout features and a key reason many professionals will be drawn to this lens. It allows for faster shutter speeds in low-light environments, better subject isolation with shallow depth of field, and consistent exposure settings throughout the zoom range. For astrophotographers especially, the wide aperture is invaluable when capturing faint celestial light, and for other creatives, it adds flexibility when shooting in dim conditions without resorting to higher ISOs.
Focusing capabilities are enhanced with a focus-by-wire design, which has become the standard among newer autofocus lenses. Although this type of focusing may not appeal to everyone, particularly those using astronomy cameras or seeking fully manual tactile control, it allows for electronic precision and smooth operation with compatible mirrorless bodies. The lens also includes a physical AF/MF switch and a responsive focus ring for intuitive adjustments, ensuring that hybrid shooters can adapt on the fly between different environments and applications.
Compatibility is broad, with the lens being made available in L-Mount, Sony E-mount, FUJIFILM X Mount, and Canon RF Mount options. All versions are optimized specifically for APS-C mirrorless sensors, and each has a tailored angle of view ranging approximately from 79.7° to 39.1° depending on the mount. Minimum focusing distance across the board is an impressive 28cm (11.1 inches), with a maximum magnification ratio of 1:4.8 at the 40mm end, ideal for close-up environmental shots, flowers, or foreground framing in astro landscapes.
All variants of the lens come with standard Sigma accessories, including a dedicated lens pouch, the LH728-02 lens hood, and front and rear caps. Each mount version has a unique barcode and physical dimension specification, but all maintain a consistent build profile that makes them equally balanced and reliable. In every respect, the Sigma 17-40mm F1.8 DC | Art is designed to meet the demands of today’s hybrid shooters, those who need top-tier optical quality for both stills and video, wrapped in a versatile, portable package that doesn’t compromise on speed, reach, or build integrity.
Nico Carver, familiar across online astrophotography circles through his Nebula Photos channel, takes us on a detailed exploration of Sigma’s brand-new 17-40?mm?f/1.8 DC | Art lens, optimized for APS-C mirrorless cameras. From the first seconds of his review, Nico makes clear that his focus is on how well this lens performs for night-sky imaging, which he argues is one of the toughest use cases for optical gear. A lens that can capture pinpoint stars across a field without chromatic aberration, distortion, or vignetting is a rare beast, and stars serve as unforgiving test subjects, illuminating any weaknesses with stark clarity.
To give that mini-lens such a demanding trial, Nico pits it against the venerable Sigma 18-35?mm?f/1.8, a lens that’s become legendary for its sharpness and image quality, but one designed for DSLR crop sensors, not mirrorless. This head-to-head matchup frames the 17-40?mm as a potential “successor,” one that could push the boundaries for astrophotographers shooting on APS-C systems. Nico’s debate centers around whether, under the scrutiny of a night-sky test, the new lens can surpass its predecessor.
With no mystery about origins or motivation, Nico begins by establishing his relationship with Sigma: the lens was provided on loan starting May 29, at Sigma’s request, but he emphasizes editorial freedom, stating clearly that Sigma had no influence over his opinions. The lens would go back the day after his review drops, emphasizing that this is an honest, time-limited test rather than a paid endorsement.
He turns next to the fundamentals: size, weight, and build. The Sigma 17, 40?mm weighs in at roughly 535?g (1.2?lb), a notable reduction from the 18-35?mm’s heftier 810?g (1.8?lb). Externally it’s nearly the same length but features a slimmer diameter, now sporting 67?mm filter threads compared to the 18-35’s 72?mm. An internal zoom mechanism keeps it sealed against dust and moisture, a property shared with its predecessor. As suggested by its name, the lens spans 17?mm at the wide end to 40?mm at the telephoto end, holding a constant, bright f/1.8 aperture throughout. For astrophotographers, that aperture combined with the expanded focal length range, from roughly a full-frame equivalent of 27-65?mm on APS-C sensors, makes it a versatile lens for both Milky Way panoramas and tighter constellation or deep-sky imaging.
Nico dives into the user experience: like its sister lens, it has a physical AF/MF switch and a focus ring. But here’s a key difference, unlike the older lens, which has fully mechanical manual focusing, the new 17-40?mm uses “focus-by-wire.” The ring sends electronic signals to adjust focus. Nico flags a downside for astro-shooters: adapters that allow manual control on astronomy cameras are currently unavailable for focus-by-wire lenses, creating a potential limitation for those who shoot tethered or with modified setups. Autofocus systems can behave unpredictably or not at all in deep-sky conditions, so full manual control is often preferred by astrophotographers.
Mount options are covered next. The lens will launch first on Sony E, Leica L, and Fuji X mounts on July 10, with a Canon RF version arriving in August. At the time of Nico’s test, he has the Canon RF version mounted on Canon’s budget-friendly R100 body, a camera that, despite its entry-level price, has proven capable under the night sky.
Turning now to testing setup: he mounts both the new 17-40?mm and the old 18-35?mm side by side using a ball head and Vixen bar on a Sky-watcher Star Adventurer 2i Pro tracker atop a sturdy tripod. Importantly, he matches their pixel scale by pairing the old lens with a Canon EOS?T7 DSLR (3.72?μm pixels) and the new lens with the R100, which shares the same pixel pitch. All tracked images are shot at ISO?1600 with shutter speeds varied to maintain consistent exposure, and he mentions that he’ll include untracked results later useful for single-exposure Milky Way work.
His systematic analysis begins with vignetting, starting at the wide end. Initial corner crops at f/1.8 show that the new 17–40?mm has more corner shading compared to the 18–35?mm; Palo diameter shrinkage naturally increases vignetting. But when stopped down to f/2.8, the two lenses become comparable, and by f/4, corner shading mostly disappears on both. He then tests the telephoto end (40?mm vs. 35?mm), discovering that vignetting is more pronounced on the new lens at f/1.8. Again, stopping down to f/2.8 clears most of the issue, with f/4 yielding virtually no vignetting.
Astrophotographers, Nico notes, can manage this kind of vignetting by capturing flat-frames in-camera, a practice standard in deep-sky imaging. With Milky Way stacking (commonly 7–8 shots), he says the vignetting isn’t problematic and can often be corrected during post-processing without flats. But for serious deep-sky work, flat-frames become essential.
He transitions into evaluating sharpness and chromatic aberration. Center crops at f/1.8 show both lenses performing extremely well, slightly less purple fringing in the 17–40?mm, with stellar points appearing round and tight. At f/2.8 and f/4, corner-to-center performance remains consistently excellent. He then checks the telephoto end, where zoom differences make the images slightly fund mentally, but even that aside, both lenses retain clarity and low chromatic aberration, with the 17–40?mm again holding a marginal edge.
The most crucial comparison comes when examining extreme corners at f/1.8 and 17?mm. In this grimmest test, where zoom optics typically falter, the older 18–35?mm legal shows more distortion with barrel, astigmatism, and lateral chromatic aberration (“seagull-shaped” stars), while the 17–40?mm produces sharper, less tinted star points, even amid wide-angle, fast-aperture stress. Stopping down to f/2.8 and f/4 almost equalizes the field, yet the new lens maintains a slight edge, especially in controlling purple-fringe aberrations.
At the telephoto extreme, 40?mm vs. 35?mm, corners at f/1.8, the newer lens shows a bit more astigmatism, and stars elongate slightly more compared to its predecessor. Nico points out that pushing the range to 40?mm likely stretches the lens’s design limits compared to the safer 35?mm zoom. But he stresses that the small amount of distortion is a worthwhile trade for the added reach, as it still delivers impressively sharp corners.
To make the evidence more visceral, Nico includes a non-tracked 15-second Milky Way example at f/1.8, ISO 3200, a typical “vertical milky way” setup capturing both foreground and sky. The stars are slightly trailing, which makes optical comparison difficult, but he affirms the lens holds its own even in a single exposure, full-frame context. The key takeaway: for one-shot Milky Way captures without tracking, the lens delivers robust optical performance.
So who should consider this lens? Nico offers both astrophotographers and general users a verdict. For those into Milky Way and wide-field night sky imagery, the 17?mm end is strong and sharp. At 40?mm, the lens excels in constellation framing or deep-sky target capturing. As a first astrophotography lens, it offers versatility: wide-angle Milky Way, untracked deep-sky stacking shots on a static tripod, and telephoto-style short stacks when a tracker is available. In his eyes it’s an excellent “first lens” before investing in star trackers or more specialized gear.
Beyond the night sky, it’s also pitched as a stellar everyday zoom for nature, street, portraiture, and landscape photographers, quiet and fast autofocus, constant aperture, and general optical quality that fits the familiar 24–70?mm full-frame equivalent sweet spot. The only caveat remains the focus-by-wire design, less ideal for users who want manual focusing via tactile mechanical connection, especially for adapters and astronomy cameras. Until clever adapters appear for mirrorless, a fully mechanical lens like the earlier 18–35?mm retains an edge there. But for most mirrorless users, Sony, Fuji, Canon RF, the new 17–40?mm holds strong appeal.
Nico brings his review to a close with a showcase composite image created using the 17–40?mm. Eight sky exposures were stacked for noise reduction, and a separate long-exposure foreground shot, without tracking, was blended in to ensure both foreground sharpness and star detail. He explains the practice of blending tracked and untracked frames to avoid foreground blur, while allowing for wider framing by shifting the camera for the foreground shot. This final image exemplifies his blend of technical rigor and creative passion.
Toward the very end, Nico touches on the artistry-meets-technology balance that makes astrophotography rewarding. He extols planning, field execution, and editing as the heart of the craft, and he mentions how Brilliant, his video sponsor, fits into that. Using interactive lessons in subjects like math, science, programming, data and visualization, a platform like Brilliant supports the problem-solving mindset astrophotographers rely on. He specifically recommends their course on visualizing data, noting that concepts like logarithmic scales play directly into processing night-sky imagery. His viewers can try Brilliant free for 30 days and receive a discount.
Nico signs off warmly, inviting viewers to leverage both technical analysis and artistic vision under the night sky, “Clear skies!” he says, a salutation that resonates with astrophotographers affirming both heaven and lens.
In summary, the video builds a compelling argument: the Sigma 17–40?mm?f/1.8 DC | Art lens is a breakthrough APS-C optic with a wide constant-aperture zoom, an intriguing step up from the older DSLR-centric 18–35?mm. Under the demanding conditions of star testing, it shows slightly elevated wide-angle vignetting (easily correctable with flats or in editing), yet delivers excellent sharpness, low chromatic aberration, and strong edge-to-edge integrity, even at f/1.8. Its increased reach to 40?mm provides added versatility for constellation framing and deep-sky stacking.
A key consideration remains the focus-by-wire design, which, while likely fine for casual or mirrorless photographers, may limit advanced astrophotographers using mechanically focused or astronomy-camera rigs. However, for mirrorless shooters seeking a fast, wide-to-tele lens that doubles as a dependable astrophotography tool, Nico’s conclusion is clear: this lens is an outstanding “first lens” that pairs well with trackers or standalone tripod setups. Add excellent everyday usability and autofocus performance, and it becomes a tool worth serious consideration.
By weaving together rigorous optical testing, real-world astrophotography environments, and visual storytelling through sample images, Nico’s review offers a full portrait of a lens ready to take crown as the “new APS-C king”, not just for daytime use, but for capturing the universe in stunning detail.
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