Summary: There are not that many (better) alternatives to Canon's EF 20mm f/2.8 USM that fall within the same price range and at the same time deliver superior performance. That might be the reason to seriously consider this lens for your ultra wide photographic needs, despite somewhat lackluster performance that the lens showed around borders and level of various artifacts at the widest aperture setting.
Summary: This 20mm is an excellent lens, often overlooked because most people can't look past big, heavy expensive zooms. This 20 USM makes pictures at least as good, is much easier to carry, and costs less. It's easily available both new and used .
Conclusion: As a wide-angle lens for cropped sensors, this lens falls a little short, with virtually all of the standard zooms giving a wider angle of view. However, on the full frame sensors that Canon are now producing, this lens still warrants its place in their line-up. Nice results combined with ease of use will ensure it will stay there for some time to come.
Pros: Good build and finish, Nice focal length on Full Frame cameras, Silent and fast autofocus., Good image quality
Cons: Not that useful on cropped sensors., Stiff manual focus ring (on example tested), Distortion worse than on modern designs (minor point), Hood not included with lens
Excerpt: The Canon EF 20mm f/2.8 USM Lens fits in a nice wide angle focal length space below the ultra-common 24-something and 28-something zoom lenses. There is a noticeable FOV (field of view) difference between 20mm and 24/28mm.
Conclusion: Our tests are supposed to answer one main question - whether or not a given instrument is worth buying. In the case of the Canon EF 2.8/20 mm the answer is unambiguous – it isn’t! Spending almost 500 $ we get picture effects that are possible to achieve using cheaper and much more universal lenses like a Tamron 17-50 f/2.8 or a Sigma 18-50 f/2.8. If the difference is not visible why should you overpay?
Cons: average image quality at the frame edge,, a bit too high chromatic aberration,, huge vignetting even on an APS-C sensor,, weak work against bright light.
Canon EF 20mm f/2.8 USM - Full Format Review / Test
21 May 2008
Conclusion: The Canon EF 20mm f/2.8 USM is not a bad lens but it shows that its design dates back to the early 90s. The technical resolution is actually pretty good with a very sharp image center and pretty good borders. The corners are also very decent at medium aperture settings. However, the lens suffers from a high degree of field curvature unless you adjust your shooting style you will end with relatively soft outer image region.
Canon EF 20mm f/2.8 USM - Review / Lab Test Report
11 May 2008
Conclusion: Since the release of the EOS system we have seen several updates to Canon ultra-wide zoom lenses but they didn't really care about their fix-focals in this range ever since their initial release back in the early 90s. The Canon EF 20mm f/2.8 USM feels a little dated by now - less so regarding its mechanical qualities but optically it isn't really something special anymore. Most good quality zooms can match its quality by now.
Summary: Główne pytanie na jakie mają odpowiadać nasze testy dotyczy tego czy dany instrument warto kupić. W przypadku Canona EF 2.8/20 mm odpowiedź jest jednoznaczna. Nie warto! Wydając prawie 2000 zł dostajemy bowiem efekty zdjęciowe, które można uzyskać tańszymi i znacznie bardziej uniwersalnymi obiektywami takimi jak Tamron 17-50 f/2.8 czy Sigma 18-50 f/2.8. A skoro nie widać różnicy, to po co przepłacać (ukłony dla Dosi)?
Pros: solidna obudowa,, świetna rozdzielczość w centrum obrazu,, bardzo dobrze korygowany astygmatyzm,, przyzwoicie kontrolowana koma,, cichy, szybki i celny autofokus
Cons: przeciętna jakość obrazu na brzegu kadru,, trochę za duża aberracja chromatyczna,, duże winietowanie nawet na matrycy APS-C,, słaba praca pod ostre światło.