Canon's first "pancake" lens -EF really fun. It is so small that it, as an objective, looks more like a 20 mm spacer ring, but feels nonetheless extremely high quality and solid and provides a surprisingly high image quality from. It uses a STM autofocus motor (Stepping motor / step motor) that enables continuous shooting while recording a movie or in Live View and a fast, quiet and accurate focusing (when the lens is used on a camera with Hybrid CMOS AF system) achieved. The EF 40mm f / 2.8 STM is ideal for street and travel photography but can of course also be used for portraits or another. For the available light photography that requires extremely low f-numbers, it's not so good in spite of his good se maximum aperture of f / 2.8. In addition, the lens would be a good image stabilizer are but that's x 23 mm big lens probably requires a bit too much for a 68 mm.
When it comes to image quality, the EF 40mm f / 2.8 STM really to settle in the high-end range. Compared with zoom lenses is the most obvious, but also in comparison with other fixed focal length lenses of similar focal length, the EF 40mm f / 2.8 STM does not need to hide. It is across sharp even at f / 2.8 across the entire image area. On full frame cameras, the EF 50mm f / 1.4 USM only slightly sharper and the EF 50mm f / 1.8 II about equally sharp (at the same aperture). If, however, an APS-C camera, the EF 40mm reaches f / 2.8 STM significantly higher resolution than the other two lenses (so it comes with the usually higher pixel density of APS-C cameras better clear). The sharpness is comparable to that of the EF-S 60mm f / 2.8 Macro USM, which can only be used on APS-C cameras and three times as large.
Although the EF 40mm f / 2.8 STM shows only low distortion ("distortion") but the focal plane of the lens when used on full-frame cameras (not to APS-C cameras) clearly arched ("curvature of field"), which in itself some Images can be felt (depending on the subject and used Aperture). Fringing ("Chromatic aberration") in sharp image areas ("lateral chromatic aberration") are clearly visible and even those that occur only in blurred image areas ("longitudinal chromatic aberration"), are present. On the positive side is the circular aperture shape that gives a pleasantly quiet background blur but the negative is to f / 5.6 (on full frame cameras) clearly visible edge shadows ("Vignette").
Overall, the image quality of the EF 40mm f / 2.8 STM is surprisingly high for a lens of this size and price. So from now on you'll always have a really good f / 2.8 prime lens have with you, which requires almost no space in the camera bag!
Canon has his first pancake lens well thought out and given him the right blend of features, image quality and an attractive price at incredibly small dimensions. I'm sure that many people will love the lens alone because of its size and feel, but the EF 40mm f / 2.8 STM also offers much more.
A much more detailed report I published together with all the test shots, specifications and sample images on my homepage LensTests_de.
