Canon 100mm f/2.8 Macro

Manufacturer: Canon Type: Macro lens Focal length: 100mm Maximum aperture: f/2.8 Generations: EF 100mm f/2.8 Macro USM (2000), EF 100mm f/2.8L Macro IS USM (2009), RF 100mm f/2.8L Macro IS USM (2021) Mount: Canon EF (first two generations), Canon RF (third generation)

Overview

The Canon 100mm f/2.8 Macro is the definitive macro lens for Canon underwater photographers, appearing in approximately 52 articles and nearly 780 forum threads across the Wetpixel archive. It is Canon’s direct counterpart to the Nikon 105mm Macro, offering the same essential advantage: sufficient working distance at 1:1 magnification to light subjects properly with strobes and avoid frightening skittish critters.

The lens’s 100mm focal length on a full-frame sensor (or effective 160mm on APS-C bodies like the EOS 20D/7D) provides approximately 5-6 inches of working distance from the front of the port to the subject at maximum magnification. This makes it ideal for photographing nudibranchs, blennies, gobies, pygmy seahorses, and other small creatures that demand close approach but spook easily (^[1]).

As bmyates noted in 2005: “If you’re also going to get the Canon 100mm macro (which you definitely should!), you might find the Sigma 50mm a better complement to it… making it more useful for dives when you might want to take a fish photo, but still want to have 1:1 macro in case you come across the rare elephant-eared flatworm!” (^[2]).

Generations

EF 100mm f/2.8 Macro USM (2000)

The first USM (Ultrasonic Motor) generation replaced an older, slower-focusing non-USM model. It became the standard Canon macro lens for underwater photography during the early DSLR era (2002-2009), paired with the Canon 10D, 20D, 5D, and 1D-series bodies.

Key specifications:

• 1:1 maximum magnification
• Minimum focus distance: 0.31m (1 foot)
• Internal focusing (lens does not change external length)
• Ring-type USM autofocus motor
• 58mm filter thread
• Weight: 580g

Underwater characteristics:

Paul Kay noted in 2005 that “Canon’s 100mm USM macro lens is a true internal focusing macro lens which does not physically alter its external dimensions between infinity and 1:1,” which simplified port design compared to older extending-barrel macro lenses (^[3]).

The internal focusing design was a significant advantage for housing manufacturers. However, the autofocus/manual focus switch on the lens barrel was positioned where it could be inadvertently knocked to manual by the port during assembly. Brad DB described the issue: “The act of adding the port to the housing tends to hit the Auto/Manual switch on the lens and leave it in the manual position” (^[4]).

The non-L version could not accept Canon’s own teleconverters (which protrude into the rear element), but third-party teleconverters from Kenko and Tamron worked well. Herb Ko reported: “I’ve used the Tamron 1.4x and 2x with the 100mm macro. The 1.4x works very well, the autofocus is still OK with it on, and the images are sharp” (^[5]).

EF 100mm f/2.8L Macro IS USM (2009)

The “L” (luxury) version added optical image stabilization and Canon’s professional-grade weather sealing, along with improved optics. It quickly became the preferred version for underwater photographers.

Key specifications:

• 1:1 maximum magnification
• Minimum focus distance: 0.30m
• Hybrid Image Stabilizer (up to 4 stops; effective for both angular and shift shake)
• Ring-type USM autofocus
• L-series weather sealing and build quality
• 67mm filter thread
• Weight: 625g
• 15 elements in 12 groups (including UD element)

Underwater characteristics:

The Hybrid IS system was specifically designed to address close-range camera shake, where shift (translational) movement dominates over angular movement. This made it more effective at macro distances than conventional IS systems optimized for telephoto use. Community discussion debated whether IS was useful underwater (since strobe duration effectively freezes motion), but many found it helpful for composing and achieving autofocus lock on moving subjects.

Bruce Yates (bmyates) tested the L version extensively, reporting: “The 100mm IS by itself (like the old 100mm but with seemingly slightly faster AF) does a great job” when paired with the Canon 5D Mark II’s 21-megapixel sensor (^[6]).

Paul Kay tested the lens with extension tubes and found it could accept up to 37mm of total extension (12mm + 25mm tubes) while maintaining acceptable image quality, though he noted diminishing returns compared to simply cropping from the 1:1 image on high-resolution sensors (^[7]).

RF 100mm f/2.8L Macro IS USM (2021)

Canon announced the RF-mount version in April 2021 as part of their mirrorless lens expansion alongside the RF 400mm f/2.8L and RF 600mm f/4L. It represented a significant advancement in macro lens capability (^[8]).

Key specifications:

• 1.4x maximum magnification (world’s first AF macro lens exceeding 1:1)
• Minimum focus distance: 0.26m
• Spherical Aberration (SA) Control ring for adjusting bokeh character
• Up to 5-stop optical IS (up to 8-stop combined IS with EOS R5/R6 IBIS)
• Dual Nano USM motors for fast, silent autofocus
• Suppressed focus breathing (beneficial for video and focus stacking)
• 9-blade circular aperture
• 67mm filter thread
• Price at launch: $1,399 USD
• Available from July 2021

Underwater significance:

The 1.4x native magnification means the lens can fill the frame with a subject area of approximately 25.7mm x 17.1mm on a full-frame sensor without any accessories — territory that previously required a diopter or teleconverter. Canon’s press release stated it was “a truly versatile lens, and a kitbag ‘must have’ for professionals, semi-professionals and enthusiasts alike” (^[9]).

The SA Control ring allows photographers to vary the look of background and foreground bokeh and create soft-focus effects — a creative tool unprecedented in a macro lens. Combined with the Canon EOS R5’s 45-megapixel sensor and coordinated IS system, the RF 100mm represents the most capable Canon macro system ever offered.

Port Requirements

The Canon 100mm macro requires a flat macro port with appropriate extension rings depending on the housing system. Because it is an internal focusing lens that does not change length, port sizing is straightforward.

Housing-specific port solutions documented in the archive:

• Ikelite: Port #5508.45 (with focus knob option). Does not accommodate filters — the lens fills the port completely. A 2.2-inch extension combined with the Mirrorless Flat Port Extended was later released for the Canon EOS 100D/Rebel SL1 housing (^[10], ^[11])
• Subal: FP-90 flat port with 33mm extension ring. No manual focus gear available for the USM version (gear existed for the older non-USM model). Ryan suggested a sewing machine belt as a DIY focus gear solution (^[12])
• Seacam: PVL120 macro port used by James Wiseman with the Canon 5D (^[13])
• Hugyfot: MP100 ALU Macro Port (100mm internal length), specifically designed for the EF 100mm f/2.8L IS USM, with conical shape for strobe access and M67 threaded front for wet lenses (^[14])
• Nauticam: Macro port with flip lens holder system for wet diopters; compatible with the Nauticam SMC/CMC system

Super Macro: Diopters and Teleconverters

The Canon 100mm macro is the foundation of most Canon super macro setups. The community extensively discussed methods for exceeding 1:1 magnification:

Wet Diopters

• Nauticam SMC-1: Provides 2.3x magnification with 50mm working distance when paired with the Canon 100mm. Explicitly listed as compatible with both the non-L and L versions (^[15])
• Inon UCL-67: Delivers up to 2.76x magnification (equivalent to +15 diopter), designed for use with 60-100mm macro lenses on full-frame DSLRs (^[16])
• Seacam wet diopter (#4): Adds approximately 1.3:1 magnification when stacked on a 100mm at 1:1. Stephen Frink reviewed it in 2005, noting he could “easily pick out my subject, even from a distance” and autofocus worked reliably (^[17])
• SubSee +5/+10: Popular third-party diopter used by many Canon shooters
• Backscatter MacroMate: Provides up to 2:1 magnification but requires closer working distance than the Seacam diopter (^[18])

Teleconverters

Canon’s own teleconverters are not physically compatible with the 100mm macro (they protrude into the rear element), but third-party options work:

• Kenko Pro 300 1.4x: Maintains usable autofocus; sharp results (^[19])
• Kenko Pro 300 2x/3x: Magnification increases proportionally but autofocus becomes very slow or unusable. Manual focus or “rocking” technique required (^[20])
• Tamron 1.4x/2x: Good compatibility; Herb Ko confirmed both work with the Canon 100mm (^[21])

Tony Wu described shooting the Canon 100mm USM with a 3x teleconverter plus diopters to achieve approximately 5x magnification, noting “the most difficult challenge with teleconverters is finding the appropriate port extensions and manual focus gears to permit manual focusing” (^[22]).

Extension Tubes

Paul Kay found the Canon 100mm USM worked well with up to 37mm of extension tubes while maintaining acceptable image quality, though he noted that internal focusing lenses produced diminishing returns with extension compared to older designs (^[23]). Ikelite’s 2015 port extension explicitly supported the EF 100mm f/2.8L Macro IS USM with a Canon Extension Tube EF 12 II (^[24]).

Community Debates

100mm vs. 60mm Macro

The Canon community frequently discussed whether to use the EF 100mm or the EF-S 60mm macro lens underwater. The consensus:

• 100mm advantages: Greater working distance for lighting and shy subjects; better for supermacro with diopters/TCs; works on both full-frame and APS-C bodies
• 60mm advantages: Faster autofocus; shorter port needed; more versatile for fish portraits on APS-C (acts as ~96mm equivalent); lighter, cheaper
• Common advice: Own both. Use the 60mm as a “walk-around macro” and the 100mm for dedicated macro dives on small critters (^[25], ^[26])

Bruce Yates advised: “If you don’t already own the 100mm lens, I’d suggest that you hold off even buying it until you’ve used the 60mm for awhile, and see if you even feel you need the 100mm” — though most serious macro shooters eventually acquired the 100mm (^[27]).

Manual Focus vs. Autofocus

The 100mm USM’s autofocus was generally praised as adequate for macro work, unlike the older non-USM version and unlike the Nikon AF-D 105mm which was notoriously slow. Multiple forum members reported successful autofocus use without needing a manual focus gear on their housing:

• “I personally haven’t had any issues using AF with the 100mm” — chilipino (^[28])
• “I found the lack of a manual focus knob not to be a problem” — braddb (^[29])

However, Ryan (a dealer) noted that “for the super macro shooting that many of my customers do, manual focus is a requirement even with the USM lens” and provided creative solutions like sewing machine belts as DIY focus gears (^[30]).

IS Usefulness Underwater

The L version’s image stabilization sparked debate. Since underwater macro shots typically use strobe light (with very short flash durations that freeze motion regardless of shutter speed), some argued IS was unnecessary. Others found it helpful for:

• Composing and locking autofocus on moving subjects in the viewfinder
• Shooting ambient-light macro (rare but useful for certain creative effects)
• Video work where strobe-freezing does not apply

Comparison with Nikon 105mm

The Canon 100mm and Nikon 105mm are direct competitors and are frequently compared in the Wetpixel archive:

Both lenses are equally compatible with the Nauticam SMC/CMC system, and both are considered first-choice macro lenses for their respective systems in underwater photography.

Notable Users

• Stephen Frink: Used the Canon 100mm macro extensively during his reviews of wet diopters, including the Seacam #4 and Backscatter MacroMate (^[31])
• James Wiseman: Used with the Seacam 5D housing for macro dives at Blue Heron Bridge (^[32])
• Paul Kay: Extensively tested extension tube compatibility and documented the lens’s optical behavior (^[33])
• Tony Wu (tonywu): Pushed the lens to extreme magnification (5x) using stacked teleconverters and diopters (^[34])
• Bruce Yates (bmyates): Tested the L version with Kenko 3x TC on the Canon 5D Mark II (^[35])

Timeline

• 2000: Canon EF 100mm f/2.8 Macro USM released, replacing the older non-USM version
• 2003-2005: Becomes standard macro lens for Canon 10D and 20D underwater shooters (^[36])
• 2005-04: Ikelite port #5508.45 discussed for Canon 20D housing (^[37])
• 2005-05: Subal housing users discuss port and manual focus options for the 100mm USM (^[38])
• 2005-11: Stephen Frink reviews Seacam wet diopters using the Canon 100mm (^[39])
• 2006-03: James Wiseman uses 100mm with Seacam 5D housing at Blue Heron Bridge (^[40])
• 2009: Canon EF 100mm f/2.8L Macro IS USM released with Hybrid IS
• 2010-06: Bruce Yates tests L version with Kenko 3x TC, reports good results on 5D Mark II (^[41])
• 2013-11: Nauticam SMC released; both Canon 100mm versions listed as compatible (^[42])
• 2015-02: Ikelite releases 2.2-inch port extension enabling 100mm L use on compact SL1 housing (^[43])
• 2017-02: Inon UCL-67 released, designed for 60-100mm macro lenses (^[44])
• 2020-05: Hugyfot releases MP100 ALU Macro Port specifically for the Canon 100mm L (^[45])
• 2021-04: Canon announces RF 100mm f/2.8L Macro IS USM with 1.4x magnification and SA Control ring (^[46])

References