Just how good is the 20/1.7?

Started Nov 9, 2012 | Questions thread
Mingjai Senior Member • Posts: 1,381
Re: Just how good is the 20/1.7?

Anders W wrote:

I have the 20 and consciously chose it over the 25, although I could easily afford either one. But that's me and I can certainly see why others might think differently. The pros and cons are in my opinion as follows:

Pros for the 20

  • Smaller
  • Lighter
  • Less expensive
  • As sharp or sharper at really wide apertures
  • At least as good bokeh if by bokeh you mean the quality rather than the quantity of the blur
  • Wider FoV makes it more useful in close quarters
  • Reportedly doesn't cause as much aperture clicking ("rattle-snaking")

Pros for the 25

  • Better low-light ability (about half a stop)
  • Can provide more background blur by means of its longer FL and greater max aperture
  • More narrow FoV gives it more reach and makes it possible to take images at close distance/high magnification without too much distortion
  • Noisefree AF (may be important for video where the noise is recorded if you AF during the clip; not otherwise)
  • Suitable for AF-C (the 20 is not)
  • Is not reported to cause lock-ups with the E-M5 (the 20 is, although I have never experienced this myself)
  • Is not reported to cause banding with the E-M5 (the 20 is, and I have seen it myself; but see further info below)

There has been much talk about the slow AF of the 20. I have tested that myself and found only a very marginal difference in ordinary AF-S compared to lenses that are known to be at least as fast (perhaps faster) as the 25. See here:


As to banding when the 20 is used on the E-M5, see here:


I have both and think this list of pros for each lens explains the reason why I keep and use both.

I suspect the 20mm is slightly wider than its nominal focal length because it's very close to my 9-18mm at 18mm. The FOV difference between the 20mm and 25mm is actually pretty different. Here's an illustration of 9-18mm at 18mm, 20mm, and 25mm:

 Mingjai's gear list:Mingjai's gear list
Olympus E-M1 Olympus M.Zuiko Digital ED 9-18mm F4.0-5.6 Panasonic Leica Summilux DG 25mm F1.4 Olympus M.Zuiko Digital ED 75mm F1.8 Panasonic Leica DG Summilux 15mm F1.7 ASPH +16 more
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