Canon EF 50mm f/1.4 USM; Canon EF 70-200mm f/2.8L IS III USM; Micro USM Lenses. The Micro USM motor isn’t connected to the element group directly. Instead, Micro USM lenses use a gear-system motor. The ultrasonic vibrations move the gears, and the gears then move the glass to focus. A Micro USM motor is similar to a DC motor. I like the image better out of the Sigma vs. the EF mkII. My copy of the EF mkII has a magenta shift (as many Canon lenses do) that in this case goes just a bit too far IMO. The Sigma rivals (though is bested by) the RF 24-70/2.8 IMO in terms of sharpness, contrast, color rendition, distortion, and flare resistance. Canon EF 28mm f/1.8 USM Performance As far as resolution is concerned, this lens disappoints, especially at apertures faster than f/2.8. At f/1.8 clarity in the centre of the image is fairly poor. Canon EF 24mm f/2.8 IS USM Add to compare DXOMARK Score : Best at f=24mm & f/2.8 34. Lens Metric Scores : Sharpness Lean and Powerful. The EF 400mm f/2.8L IS III USM offers you the superb image quality of a Canon L series super telephoto in a new, lightweight form that makes it the world’s lightest 400mm f/2.8 lens*. A meticulous optical redesign means reduced flare and ghosting thanks to Super Spectra Coating (SSC) and Air Sphere (ASC), a shorter minimum Options. 10-02-2018 08:19 AM. I would go with the EF 28mm f/2.8 IS USM. I owned the EF 28mm f/1.8 USM briefly but sold it because I found it was not sharp wide open. Most reviewers say the EF 28mm f/1.8 USM is soft wide open, and even when stopped down to f/2.8, it is still not as sharp as the IS lens wide open at at f/2.8. Mike Sowsun. The Canon EF 24mm f/2.8 IS USM lens is the ideal entry focal length into the world of ultra wide-angle photography. A compact, fixed focal length 24mm lens equipped with Canon's Optical Image Stabilizer technology that offers up to 4 stops of shake correction along with a ring-type USM and advanced CPU with optimized AF algorithms for fast auto focusing. Now waiting for it to be delivered 😄. They say the Canon 17-55mm f2.8 is an L quality lens. If you want to save a bit, get the Sigma 17-50mm f2.8. Reviews said it's only slightly less sharp (not worth the price difference in difference in quality) and is shorter in physical size. o2iGT.