Panasonic Lumix G 20mm f/1.7 ASPH Lens

      Photo Review 8.5

      In summary

      A fast, ultra-compact prime lens for Micro Four Thirds System cameras.Launched at the same time as the Lumix DMC-GF1 camera Panasonic’s Lumix G 20mm f/1.7 ASPH. lens will be offered with the camera body and makes an attractive kit option for serious photographers. Compact enough to make the GF1 a pocketable option, it also provides a fast f/1.7 maximum aperture that lets photographers shoot with a shallow depth-of-field. . . [more]

      Full review


      Launched at the same time as the Lumix DMC-GF1 camera Panasonic’s Lumix G 20mm f/1.7 ASPH. lens will be offered with the camera body and makes an attractive kit option for serious photographers. Compact enough to make the GF1 a pocketable option, it also provides a fast f/1.7 maximum aperture that lets photographers shoot with a shallow depth-of-field.


      Side view of the Lumix G 20mm f/1.7 ASPH. lens showing its ‘pancake’ design. (Source: Panasonic.)

      The optical design consists of seven lenses in five groups with two aspherical elements to counteract distortion and chromatic aberrations. The 20mm focal length is equivalent to 40mm on a 35mm camera, providing a good, general-purpose lens that can be used for many types of subjects. Seven aperture blades close to a rounded aperture for attractive bokeh at wide aperture settings, while multi-coatings minimise the incidence of flare and ghosting.

      This lens has been designed to support the advanced contrast-based autofocusing system provided by Panasonic’s G-series cameras and is compatible with the Face Recognition system provided in the latest models.

      Build and Handling
      Despite its relatively light weight (roughly 100 grams) the Lumix G 20mm f/1.7 ASPH. lens is solidly built with a metal mounting plate that ensures long-term performance reliability. The lens barrel is made from lightweight aluminium alloy and carries a red dot that is matched to a similar mark on the camera body when the lens is attached.

      Towards the front of the lens barrel lies a 10mm wide focusing ring, which has a ridged rubber coating. This ring moves very smoothly and positively, making accurate manual focusing straightforward. In front of it the barrel is threaded to accept 46 mm filters. Aperture settings range from 1/1.7 to f/16 in 1/3 EV steps.


      Angled front view showing the position and relative size of the front element. (Source: Panasonic.)

      The front element of the lens has a diameter of approximately 20 mm and is slightly recessed. The lens is supplied with front and rear caps and a soft carrying pouch but no lens hood is provided.

      Although it provides only one focal length setting, photographers who are prepared to think laterally will soon find ways around its limitations. We were able to achieve excellent wide-angle coverage by shooting vertical panoramas (an example is included in the Sample Images section below).

      The close focusing limitation of 20 cm can also be overcome in several ways. If you shoot raw files and convert them in Adobe Camera Raw you’ll find plenty of resolution to support cropping. There’s even enough for cropping to achieve a moderate zoom effect.

      Our tests on this lens were carried out on the GF1 body (a review of which is posted on the Photo Review website. Click here to read the review). Imatest showed it to be capable of high resolution through its aperture range, with the highest performance being between f/3.2 and f/7.1. The graph below shows the results of our tests on both JPEG and raw files.


      Edge sharpness was generally very good and lateral chromatic aberration was negligible across all aperture settings, as shown in the graph below (the red line at the right hand edge of the graph marks the border between ‘negligible’ and ‘low’ CA).


      Slight vignetting was detected at f/1.7 but this was gone by f/4.5 and vignetting was negligible at smaller apertures. Rectilinear distortion was also negligible. The wide aperture also provided a bright enough image to support manual focusing after dark. In bright conditions, flare and ghosting were relatively low.

      Close-up capabilities of the test lens are fairly limited, due to a minimum focusing distance of 20 cm. However, bokeh at wide aperture settings was smooth and attractive.

      Buy this lens if:
      – You want a fast lens for available light photography and require high performance across a wide aperture range.
      – You require distortion-free images.
      – You have a compatible camera body.
      Don’t buy this lens if:
      – You really need a zoom lens.
      – You shoot lots of close-ups.


      A complete set of Imatest graphs for JPEG and raw files can be found in the review of the GF1 camera.



      Vignetting at f/1.7.


      Vignetting at f/5.6.


      Close-up at f/1.7; ISO 100, 1/500 second.


      ISO 100, 1/30 second at f/11.


      ISO 100, 1/400 second at f/8.


      ISO 100, 1/200 second at f/16.


      Flare; ISO 100, 1/160 second at f/8.


      A panorama stitched together from four vertical JPEG images captured with the GF1 and 20mm lens.

      Additional image samples can be seen at the end of the review of the Panasonic Lumix DMC-GF1 camera.




      Picture angle: 57 degrees
      Maximum aperture: f/1.7
      Minimum aperture: f/16
      Lens construction: 7 elements in 5 groups (includes 2 non-spherical lenses)
      Lens mount: Micro Four Thirds System
      Diaphragm Blades: 7
      Minimum focus: 20 cm
      Maximum magnification: 0.13x (equivalent to 0.25x in 35mm format)
      Filter size: 46 mm
      Dimensions (Diameter x L): 63 x 25.5 mm
      Weight: Approx. 100 grams





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      Rating (out of 10):

      • Build: 9.0
      • Handling: 9.0
      • Image quality: 9.0
      • Versatility: 8.0
      • OVERALL: 8.5