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I enjoyed shooting with pancake lenses on my Olympus Pen and wanted one for my EOS gear. The EF 40 2.8 STM, Canon's first DSLR pancake, debuted Summer 2012 and caused a stir due to low cost and high optical quality. Here's my take on this able little optic.

Downtown Honolulu | EOS SL1 and EF 40 2.8 STM

This review consists of my opinions and observations as a hobbyist. No scientific measurements, MFT charts or pixel peeking comparisons will be found here.

Compatibility

The EF 40 2.8 STM lens works on all Canon EOS DSLR cameras, both full frame and APS-C (1.6X), such as the EOS 6D MK II and Rebel SL3. It will also work on EOS R and M series mirrorless cameras with a mount adapter. It does not fit non-Canon cameras such as Pentax, Nikon, Fuji, etc.

EF 40 2.8 STM | Sharp and tiny (image courtesy Canon)

Build

Although a small lens, it feels solid in hand, boasting excellent build: metal mount, beefy plastic barrel and comely industrial satin finish. The AF/MF feels sturdy and is unlikely to be inadvertently moved.

Auto Focus

STM AF on other lenses is normally silent during movie servo and pulls. However, the EF 40 2.8 STM AF isn't silent, making a soft electronic intonated "sheeeeet," resembling a sound effect from Tron. I suspect this sound is the mechanical linkage, not the motor, but built-in camera mics pick it up during video recording. The work around is to use an external mic, outboard audio or prefocus before the clip. Focus is slower than ring-USM but silky smooth for movie servo and pulls.

The motor uses "focus-by-wire" manual focus. This means the focus ring isn't mechanically coupled to the lens, but is simply a switch for activating the focus motor. MF is smooth and accurate, albeit slow. The gotcha it's only active when the shutter button is half depressed. The nested barrel extends during focus operation.

Black Cat Tattoo | EOS SL1 and EF 40 2.8 STM

I use the EF 40 2.8 STM on a 6D, 5D MK II and SL1. AF is dependable on the 5D MKII and 6D, but randomly misses on the SL1 15 to 20% of the time, especially when refocusing on the same point in a subsequent photo. The EF-s 24 2.8 STM, a similar design to the EF 40 2.8 STM, also randomly misses AF on the SL1 albeit not as often. Other lenses focus fine on the SL1, even slow zooms like the EF-s 10-18 4.5-5.6 IS STM.

Image Quality

Wide open at F2.8 my first copy was sharp in the center of the frame but suffered very soft corners on both full frame and APS-C. Corners improved when stopped down to F8 but were still unacceptably soft. Night images with points of light exhibited strong coma (comet-like tail) at F2.8. Stopping down reduced but didn't eliminate coma. If you look closely at the harbor picture below, coma is visible on most points of light, especially towards the edges.

For the above reasons, I returned my first copy and bought a refurbished EF 40 2.8 STM directly from Canon. What a difference! Wide open, it was deadly sharp in the center. Corners were much improved but still a little soft on full frame. On APS-C the corners were nearly as sharp as the center. And coma was greatly reduced: no coma center frame at F2.8 and only slight coma along the periphery. So second time around a home run!

Defocused areas (bokeh) have a pleasant smooth swirl to them at F2.8, helping offset subjects from background. I find 40mm a natural snapshot FOV for full frame cameras like the 6D. The slightly wide view is perfect for landscapes and environmental portraits. Keep in mind, on APS-C cameras, e.g., 60D, 70D or Rebels, FOV is a 64mm equivalent, falling within the realm of short telephoto.

Sun Yat-Sen | EOS Rebel SL1 and EF 40 2.8 STM

Lens Hood

Canon makes a dedicated hood for this lens, the ES-52 Lens Hood. It's just a 52mm aluminum filter ring around a disk with a hole in the center. It provides some shade but not much. The 40 2.8 is so popular there's a Chinese knockoff of the ES-62 available for a few bucks less: Rainbow Imaging HES52. If you want more protection, a generic screw-in type like the Rainbow Imaging HM52 Metal Lens Hood is better but will spoil the minimalist pancake vibe. I elected to use the ES-52, buying when the price drifted down to $18.

Canon ES-52 Lens Hood (image courtesy Canon)

1914 Fort Street, Honolulu | EOS Rebel SL1 and EF 40 2.8 STM

Last Blurb

Normally $150 doesn't buy much in terms of optics but the EF 40 2.8 STM is an exception to the rule. This lens is sturdy, renders beautiful images and is barely larger than a body cap. If you get a good copy, it's an excellent optic. A basic 6-element design and offshore manufacturing (Malaysian factory) helped reduce costs but compromises in quality control were obviously made to maintain this price point. Test your lens for sharpness and coma before the return period is up. I got a great sample the second try so it all ended well after some chuck 'n jive with the man.

Finally, please help support this website by purchasing this lens at Amazon.

Downtown Honolulu | EOS 5D MK II and EF 40 2.8 STM

Specifications

Focal Length: 40mm

Aperture: F2.8 to 22

Lens Construction: 6 elements in 4 groups

Min. Focusing Distance: 0.98 ft./0.3m

Maximum Magnification: .17x

Angle of View (Diagonal): 57°30' (full frame)

No. of Diaphragm Blades: 7

Filter Size: 52mm

Diameter & Length: 2.7 x 0.9 inch / 68.2 x 22.8mmWeight: 4.6oz / 130g

Included Accessories: lens caps

Cost: $199 (MAP)

09/16/2014 | Edited 04/16/2023