The Panasonic Lumix G 20mm F1.7 lens is a pancake-style prime lens for Micro Four Thirds system cameras. In the Micro Four Thirds format, it is slightly wider than normal. It was the prime-lens option available with the GF1.

Lumix 20mm

Maker	Panasonic
Lens mount(s)	Micro Four Thirds
Part number	H-H020
Technical data
Focal length	20mm
Focal length (35mm equiv.)	40mm
Aperture (max/min)	f/1.7 - f/16
Close focus distance	0.2 m (7.87 in)
Max. magnification	0.13
Construction	7 elements in 5 groups
Features
Lens-based stabilization	No
Macro capable	No
Physical
Max. length	25.5 mm (1.0 in)
Diameter	63 mm (2.48 in)
Weight	100g (3.53 oz)
Filter diameter	46mm
History
Introduction	2009

The lens is "focus by wire"- the focusing ring sends commands, while the actual actuation is via a motor, even for manual focus. The front element does not rotate, allowing the consistent use of polarized filters. The 46mm thread lets a Micro Four Thirds user share filters between it, the Panasonic 14mm, Panasonic Leica 25mm, and Panasonic Leica 45mm lenses.

Focusing shifts all lens elements by the same amount, increasing the length of the lens slightly at close focus distances.

The lens is very favorably reviewed^{[1] [2]} , including descriptions as a "must have"^{[3] [4] [5] [6]} or "must own"^[2] lens. Praise centres on its small size and excellent sharpness. Criticisms include the use of software correction of distortion, and that the focusing motor is slower and noisier than lenses intended for video ("MSC"- movie and stills compatible).

In 2013, an updated version of this lens called the Panasonic Lumix G 20mm F1.7 II was released. It has the same length and optical construction as the original, but it is lighter at 87 grams and has a different exterior design.^[7]