Sigma 15mm f/2.8 EX DG Diagonal Fisheye

Manufacturer: Sigma Type: Lens (diagonal fisheye) Year introduced: 1999 (updated to EX DG version ~2003) Mount: Nikon F, Canon EF, Sigma SA, Pentax K Format: Full-frame (FX) — also usable on DX/APS-C with reduced field of view Field of view: 180 degrees diagonal (on full-frame sensor) Maximum aperture: f/2.8 Minimum aperture: f/22 Minimum focus distance: 15 cm (5.9 inches) from the front element Filter: Rear gel holder Optical construction: 7 elements in 6 groups Weight: 370g Dimensions: 73.5mm diameter x 65mm length

Overview

The Sigma 15mm f/2.8 EX DG Diagonal Fisheye was the standard full-frame fisheye lens for underwater photography for over 15 years. Available in both Nikon and Canon mounts, it served as the go-to wide-angle option for FX shooters from the introduction of the Canon 5D (2005) and Nikon D3 (2007) through the mid-2010s, when the Canon 8-15mm f/4L and Nikon 8-15mm f/3.5-4.5E gradually superseded it.

The lens’s key advantage over competing full-frame fisheyes was its significantly closer minimum focus distance — 15 cm (5.9 inches) from the front element compared to 20 cm (7.9 inches) for the Canon 15mm f/2.8 Fisheye and 25 cm for the Nikon 16mm f/2.8 AF Fisheye-Nikkor. This closer focus became even more significant underwater, where the lens focuses on the virtual image created by the dome port. As Alex Mustard explained: “These differences actually become more significant underwater because the lens is focusing on a virtual image. For close focus wide angle I strongly favour the Sigma 15mm over the Nikon 16mm, for this reason” (^[1]).

Mustard also noted in his Nikon D3 review that he “chose the Sigma 15mm fisheye over the Nikon 16mm (of which I own two) because I prefer its closer focus and find it sharper than the aging Nikon” (^[2]).

The lens was widely available and affordably priced, making it accessible to amateur and professional underwater photographers alike. By 2022, used copies with adapters could be found for around $250, giving it continued relevance even in the Sony mirrorless era (^[3]).

Specifications

Why It Dominated Underwater Full-Frame Photography

The Sigma 15mm became the standard full-frame fisheye underwater for several interconnected reasons:

• Closer focus than alternatives — At 15 cm minimum focus distance, it significantly outperformed the Nikon 16mm (25 cm) and Canon 15mm (20 cm) for close-focus wide-angle work. This advantage was amplified underwater where lenses focus on the dome port’s virtual image (^[4]).

• Multi-mount availability — Available in both Nikon F and Canon EF mounts, it was the only fisheye that could serve photographers on either system, making it the universal recommendation regardless of brand loyalty (^[5]).

• Sharper than Nikon 16mm — Community consensus and Alex Mustard’s direct comparison found the Sigma “marginally sharper” than the aging Nikon 16mm design, while the Nikon had better flare resistance (^[6]).

• Modern optical design — As a newer design than the 1980s-era Nikon 16mm, it incorporated better coatings and glass. Forum member dhaas summarized the consensus: “the Sigma 15mm focusses closer plus being a ‘newer’ design is the best choice” (^[7]).

• Excellent performance behind dome ports — The lens produced sharp results even behind smaller dome ports. On APS-C sensors, it was “sharp right up to the edges” even behind a 6-inch Ikelite dome (^[8]).

• Affordable price — Significantly less expensive than Canon’s own 15mm fisheye, making it the value choice for Canon full-frame shooters.

Dome Port Requirements

The Sigma 15mm required careful dome port selection, particularly on full-frame cameras where its full 180-degree field of view was utilized.

Full Frame (FX) — 8-inch Dome Required

On full-frame bodies like the Canon 5D or Nikon D3/D700/D800, the Sigma 15mm required an 8-inch (200mm+) dome port for vignette-free results. Six-inch domes vignetted severely — one user reported that on the Canon 5D with an Ikelite 6-inch dome (port 5503), “None of the 6” domes will work with the sigma 15mm. You have to use the 8” dome” (^[9]).

Full Frame — Smaller Domes for CFWA

For close-focus wide-angle work on full frame, Alex Mustard concluded that 140-150mm (approximately 5.5-6 inches) was “the sensible lower limit with a fisheye on full frame.” He used the Sigma 15mm extensively with both his custom 150mm acrylic dome and the Nauticam 140mm glass dome, shooting coral details and oceanic whitetip sharks with the Nikon D750 (^[10]).

Mustard established a scaling principle for dome size versus format: “I use an 80mm dome with the 8mm on the 2x crop, a 100mm port with the 10mm on the 1.5x crop and a 150mm port with the 15mm on the 1x crop. This for me is the lower limit of acceptable quality” (^[11]).

APS-C (DX) Sensors

On crop sensor cameras, the Sigma 15mm provided a narrower (~100-degree) field of view and could work well behind smaller domes, even a 6-inch port. Forum users confirmed sharp results “right up to the edges on my APS-C sensor Canon dSLR” behind a 6-inch Ikelite dome (^[12]).

Seacam

Stephen Frink documented that on the Canon 1Ds Mark II, the lens was “excellent with superdome” but “performs relatively poorly in corners with fisheye port.” He noted: “Clearly, even though both Canon 15mm and Nikon 10.5mm are 180 degrees, there is a difference in the optical formula” — the Sigma/Canon 15mm required a larger dome than the shorter Nikon fisheyes (^[13]).

Nauticam

The Nauticam port chart listed the 140mm glass dome as the most optimized port for the Sigma 15mm on full frame, though the 8.5-inch and 230mm domes were also compatible. The lens required a specific port extension (Nauticam 35.5mm adapter) when used with adapters on Sony bodies (^[14]).

Ikelite

Required the 8-inch dome port on full-frame bodies. The standard 6-inch dome (port 5503) was explicitly incompatible on full frame, producing heavy vignetting even with the dome shade removed (^[15]). On APS-C bodies, the 6-inch dome worked acceptably.

Key Users

• Alex Mustard — Used the Sigma 15mm as his primary full-frame fisheye from the D3 (2008) through the D4 and D750 era. He paired it with Seacam and Nauticam housings, both with and without teleconverters. He used it for his D3 review in British Columbia and Guadalupe (^[16]), his D750 review in the Red Sea (^[17]), and his Nauticam 140mm dome review (^[18]).

• Julian Cohen — Used the Sigma 15mm with his Nikon D4 as one of his primary wide-angle lenses, preferring it over the Nikon 16mm because “it focuses much closer than the Nikon” (^[19]).

• Jean Bruneau — Technical advisor to Aquatica, used the Sigma 15mm fisheye on his D800 cameras as his standard wide-angle option (^[20]).

• James Wiseman — Used the Canon 15mm fisheye (same optical class as the Sigma) with his Seacam 5D housing, producing images with Magic Filters at the Sugar Wreck (^[21]).

• Adam Hanlon — Used the Sigma 15mm for the Wetpixel D800 camera review, which was loaned by Ryan Canon of Reef Photo for the purpose (^[22]).

Comparison to Other Fisheye Lenses

vs. Nikon 16mm f/2.8 AF Fisheye-Nikkor

Alex Mustard’s direct comparison: “Both work really well. And both have much better IQ than the Tokina. I would say that the Sigma 15mm is marginally sharper and the Nikon is better at resisting flare. The Sigma focuses considerably closer. I think if you have one, then there is no point in switching. Both are excellent performers” (^[23]).

The Nikon 16mm had superior flare resistance, making it the better choice when incorporating the sun in shots. The Sigma’s closer focus made it superior for CFWA. Several users noted the Sigma had a slightly warmer color rendition than the Nikon (^[24]).

vs. Canon 15mm f/2.8 Fisheye

The Canon and Sigma shared 180-degree diagonal coverage but the Sigma focused closer (5.9” vs. 7.9” minimum focus distance). Forum consensus was “there isn’t much to choose between the two” optically (^[25]). The Sigma was typically less expensive.

vs. Nikon 10.5mm f/2.8G ED DX Fisheye

The Nikon 10.5mm served DX shooters while the Sigma 15mm served FX shooters. The 10.5mm had even closer focus and better depth of field (due to shorter focal length), making it superior for CFWA on DX behind mini domes. The Sigma was the natural step-up lens when photographers migrated from DX to full frame.

vs. Tokina 10-17mm f/3.5-4.5 DX Fisheye

The Tokina was DX-only, offering zoom flexibility the Sigma lacked. Alex Mustard noted the Sigma and Nikon 16mm both had “much better IQ than the Tokina” (^[26]). However, the Tokina’s zoom range and compatibility with mini domes made it dominant on DX, while the Sigma ruled on FX.

vs. Canon 8-15mm f/4L Fisheye USM

The Canon 8-15mm (announced 2010, shipped 2011) was the Sigma’s eventual successor for Canon full-frame shooters. It offered zoom from circular fisheye (8mm) to diagonal (15mm), superior optical quality, weather sealing, and L-series build. One user asked how the 8-15mm compared “at the 15mm end with the Canon 15mm and the Sigma 15mm” (^[27]). By 2023, Alex Mustard declared the Canon 8-15mm “the best fisheye choice currently” (^[28]).

vs. Nikon 8-15mm f/3.5-4.5E ED

The Nikon 8-15mm (shipped 2017) was the Sigma’s successor for Nikon full-frame shooters, offering modern optics, zoom flexibility, and Nano Crystal Coat for flare resistance (^[29]).

Use with Teleconverters

Alex Mustard frequently paired the Sigma 15mm with a Kenko 1.4x teleconverter on full-frame bodies, creating a 21mm f/4 equivalent that maintained the fisheye character with reduced coverage. He used this combination extensively with the Nikon D750 and Nauticam 140mm dome, shooting oceanic whitetip sharks in the Red Sea (^[30], ^[31]).

Sony Mirrorless Adaptation

The Sigma 15mm gained a second life in the Sony mirrorless era through mount adapters. Users employed the Sigma MC-11 adapter (for Sigma SA mount versions) or Metabones adapters (for Canon EF mount versions) to use the lens on Sony A7-series bodies.

Community experiences were mixed:

• On the Sony A7III with MC-11 adapter, autofocus was reported as “pretty fast” and functioning well for general use (^[32]).
• On the Sony A7RIII with Canon EF mount and MC-11, users reported no focusing issues even for close-range subjects (^[33]).
• On the Sony A1 with MC-11, one user reported the autofocus was “absolutely dissatisfied” at close range, with clownfish subjects being “already problematic” for focus lock (^[34]).
• On the Sony A7RIV, another user reported severe issues: “The camera is like crazy. It switches itself between AFS and AFC. Occasionally it focuses or the screen goes black” (^[35]).

The adapter compatibility was mount-dependent: the Sigma SA mount version with MC-11 (SA-E) was the officially supported path, while the Canon EF mount version via MC-11 (EF-E) was not officially listed as compatible but worked for many users. Users were advised to keep adapter firmware updated (^[36]).

Community Discussion

The Sigma 15mm generated extensive discussion across the Wetpixel forums:

• Fisheye lenses - Sigma 15mm or Nikon 16mm (8 replies) — Direct comparison thread where Alex Mustard provided his definitive verdict: both excellent, Sigma sharper and focuses closer, Nikon resists flare better (^[37])
• Fisheye lens for full frame (7 replies) — Canon 5D Mark II users discussing full-frame fisheye options, with the Sigma’s closer focus highlighted as its key advantage (^[38])
• 5D fisheye and Ikelite dome (5 replies) — Critical dome port compatibility discussion establishing that the Sigma 15mm requires an 8-inch dome on full-frame Canon bodies (^[39])
• Trying to decide between fisheyes (23 replies) — Early 2004 thread comparing the Sigma 15mm to the Nikon 10.5mm on DX, with James Wiseman advising the Sigma as the more “general purpose” choice (^[40])
• Canon 8-15mm fisheye - anyone tried it? (28 replies) — Discussion of the Sigma 15mm’s eventual replacement, with users asking how the 8-15mm compared (^[41])
• Sigma 15 fisheye focussing issue (6 replies) — Technical discussion of back-focus problems with the D800’s outer autofocus points (^[42])
• Deciding fisheye/WA option for Sony A7RII (11 replies) — 2022 thread discussing the Sigma 15mm as a budget fisheye option for Sony mirrorless via adapter (^[43])
• Sony 28mm fisheye converter — Thread where the Sigma 15mm via adapter was recommended over Sony’s converter as a “much better choice” for Sony shooters (^[44])

Known Issues

• Warm color cast — Multiple users noted the Sigma produced slightly warmer colors than equivalent Nikon and Canon fisheye lenses, though this was easily corrected in post-processing (^[45]).
• Flare susceptibility — Less resistant to flare than the Nikon 16mm. Alex Mustard chose the Nikon 16mm specifically “when I want to incorporate the sun in my shots” (^[46]).
• D800 outer AF point back-focus — Users reported consistent back-focus when using outer autofocus points on the Nikon D800, though center point and live view focus were accurate (^[47]).
• Port requirements on full frame — Required an 8-inch dome minimum on full-frame bodies; the common 6-inch domes produced unacceptable vignetting (^[48]).

Timeline

• ~1999: Sigma introduces the 15mm f/2.8 Fisheye lens in its original version
• ~2003: Updated to EX DG version with improved coatings and multi-mount compatibility
• 2004-06: James Wiseman recommends the Sigma 15mm as a “much more general purpose lens” than the Nikon 10.5mm for DX shooters, and Ikelite publishes sample images shot with the Sigma 15mm and Digital Rebel (^[49])
• 2005-03: Users discuss the Sigma 15mm’s compatibility with the new Ikelite 8-inch dome port (^[50])
• 2005-09: Canon 5D launches, creating the first affordable full-frame DSLR market where the Sigma 15mm becomes the standard fisheye
• 2006-03: James Wiseman uses the Canon 15mm fisheye with the Seacam 5D housing on Wetpixel shark trip (^[51])
• 2006-04: Sea & Sea announces DX-D200 and DX-5D housings; users ask about Sigma 15mm dome compatibility (^[52])
• 2006-12: Stephen Frink documents that the 15mm fisheye works with Seacam superdome but not fisheye port on Canon full frame (^[53])
• 2007-10: Community confirms Sigma 15mm requires 8-inch dome on Canon 5D with Ikelite housing; 6-inch dome vignettes even with shade removed (^[54])
• 2008-09: Alex Mustard uses the Sigma 15mm for his Nikon D3 field review, choosing it over his own Nikon 16mm lenses for its “closer focus” and greater sharpness (^[55])
• 2009-01: Community debate between Sigma 15mm and Nikon 16mm for FX migration; Mustard pronounces both “excellent performers” with Sigma marginally sharper and closer-focusing (^[56])
• 2009-12: Mustard clarifies that for CFWA he “strongly favours the Sigma 15mm over the Nikon 16mm” due to close focus advantage amplified by dome optics (^[57])
• 2012-08: Adam Hanlon uses the Sigma 15mm (loaned by Reef Photo) for the Wetpixel D800 camera review with Nauticam housing and Zen 230mm dome (^[58])
• 2013-03: Users report Sigma 15mm back-focus issues with D800 outer AF points (^[59])
• 2014-11: Mustard reviews the Nauticam 140mm dome using the Sigma 15mm on D750, establishing 140-150mm as the minimum dome size for full-frame fisheye (^[60])
• 2014-11: Sigma 15mm used with Kenko 1.4x TC for D750 field review, shooting sharks and dolphins in Red Sea (^[61])
• 2015-05: Jean Bruneau and Julian Cohen both cite the Sigma 15mm as their current FX fisheye in Wetpixel’s “Ask the Pros: Wide-Angle” feature (^[62])
• 2017-05: Nikon ships the 8-15mm f/3.5-4.5E ED, the Sigma 15mm’s successor for Nikon shooters (^[63])
• 2019-2022: Sigma 15mm gains second life on Sony mirrorless bodies via MC-11 and Metabones adapters, with mixed autofocus results (^[64], ^[65])
• 2023: Alex Mustard declares Canon 8-15mm “the best fisheye choice currently” for Sony shooters via adapter, effectively marking the Sigma 15mm’s retirement from top-tier use (^[66])

References

Wetpixel Live