Excerpt: The Canon EF 40mm f2.8 STM is the company's first 'pancake' lens, designed to be as small and light as possible. Measuring just 22.8mm thick, it protrudes to roughly the same degree as the grip on many DSLRs, and at 130g you'll hardly notice it when mounted.
Summary: The EF 40mm F2.8 STM offers excellent image quality in a tiny, well-made package. For APS-C users it provides a great carry-everywhere complement to a kit zoom, and for full frame shooters it's an excellent general-purpose 'normal' lens.
Pros: Very good optics, Tiny size, Silent autofocus, Responsive electronic manual focus, Decent construction, Low price
Cons: Can be susceptible to flare, No lens hood supplied, AF speed isn't the fastest
Excerpt: Handling and features The Canon EF 40mm f/2.8 STM is a slim, compact pancake type lens, which is compatible with Canon EF and EF-S camera bodies and costs around £230. A fast f/2.8 aperture should make this lens ideal for taking pictures in reasonably low light conditions and focusing is powered by...
Conclusion: lens, the image quality delivered was beyond what I expected from a lens at this price point. I do wish the manual focus feel was a bit more responsive, and the AF speed just a touch faster, but I can certainly live with it as-is and have no issues.
Conclusion: You might be wondering why you wouldn't choose Canon's famously good-value 50mm f/1.8 lens. At around Â£85 it's certainly cheap, but having owned one for a couple of years, we can honestly say that it's not got the quality or sharpness of the 40mm. It's also nowhere near as compact. www.canon.co.uk
Canon EF 40mm f/2.8 STM - APS-C Format Review / Test Report
26 September 2012
Conclusion: The Canon EF 40mm f/2.8 STM represents a bit of a debatable concept on a DSLR - at least when compared to the much smaller mirrorless camera system. Honestly speaking there is also not really much of a size and weight advantage when thinking of its closest cousin - the Canon EF 50mm f/1.8 - which is...
Conclusion: The STM design for quieter video autofocus is only compatible with the 650D and 5D Mark III, but as a standard fixed 40mm lens it works really well with all Canon DSLRs, with a size and price that are hard to ignore.
Pros: Versatile, small and light, Sharp images, Silent autofocus in video mode on 650D and 5D Mark III
Cons: Auto/manual focus switch a little fiddly, Quiet autofocus feature only with the above models
Excerpt: On 8 June 2012 the Canon EF 40 mm f/2.8 STM, a full frame pancake lens, was launched along with the Canon EOS 650D reflex camera. It was a huge surprise. Never before the Canon company offered a „pancake” device in the EF system.