Date introduced September 2009
Maximum format size Micro Four Thirds
Focal length 20mm
35mm equivalent focal length 40mm
Diagonal angle of view 57°
Maximum aperture F1.7
Minimum aperture F16
Lens Construction • 7 elements/ 5 groups
• 2 Aspherical elements
Number of diaphragm blades 7, rounded
Minimum focus 0.2m / 0.66ft
Maximum magnification Approx 0.13x
AF motor type DC Micro motor
Focus method Unit focus
Image stabilization No
Filter thread • 46mm
• Does not rotate on focus
Supplied accessories* • Front and rear caps
• Lens case
Weight 100g (3.5 oz)
Dimensions 63mm diameter x 25.5mm length
(2.5 x 1.0 in)
Lens Mount Micro Four Thirds

The Panasonic 20mm F1.7 pancake does rather well in our studio tests. Distortion is being corrected in software, as is lateral chromatic aberration when used on Panasonic camera bodies (although not on the Olympus E-P1), and this is reflected in the results for these tests. Compared to the Olympus M Zuiko Digital 17mm F2.8, the Panasonic simply shines - it's much sharper (to the extent of being better at F1.7 than the Olympus is at F2.8), and has lower CA (even before software correction), less falloff and lower distortion (both 'native' and corrected). Overall very impressive results for a lens this small.


Sharpness Sharpness results are extremely good; the lens is very sharp in the center even wide open, and while the corners are somewhat soft at F1.7, they sharpen up rapidly on stopping down. Optimum results are obtained between F2.8 and F6.3; stopping down further sees sharpness progressively fall due to diffraction (mercifully Panasonic doesn't provide apertures smaller than F16). 
Comparison of results obtained using the Panasonic G1 and Olympus E-P1 show slightly better results on the former - the gradual attenuation of MTFs by the E-P1 at higher frequencies indicates a slightly stronger low-pass filter.
Chromatic Aberration When used on Panasonic bodies, lateral chromatic aberration is corrected in software and is effectively removed. However this isn't the case using the Olympus EP-1, and on this camera fringing is visible (although not hugely objectionable).
Falloff We consider falloff to start becoming a potential problem when the corner illumination falls to more than 1 stop below the center. We measure 1.7 stops falloff wide open, which disappears on stopping down to around F2.8 - this is unlikely to be noticeable in normal use.
Distortion Distortion is being corrected in software, with absolutely neutral results returned on both the G1 and E-P1.

Macro Focus

The 20mm does as well as can be expected given its field of view. Maximum magnification is 0.14x, achieved at a measured closest focus of 18cm and a working distance of about 13cm from the front element to the subject.

Center sharpness is very good wide open, although unsurprisingly the corners are soft. Stop down to F4, though, and our flat-field chart test is sharp right across the frame. At this short focus distance, though, some residual barrel distortion and chromatic aberration is visible (although it's only very slight).
Macro - 122 x 92 mm coverage
Distortion: Very slight barrel
Corner softness: Low 
Focal length: 20mm (40mm equivalent)