Panasonic/Leica's extraordinary MFT ultra-wide zoom — constant f/1.7 from 20-50mm equiv, a world first.
The Panasonic Leica DG Vario-Summilux 10-25mm f/1.7 ASPH (H-X1025) was released in 2019 as the fastest constant-aperture zoom for Micro Four Thirds, covering 20-50mm full-frame equivalent at constant f/1.7. Seventeen elements in 12 groups. Nine rounded aperture blades. 77mm filter thread. At 690g. 28cm MFD. Dust and splash proof.
The optical design uses 17 elements in 12 groups (3 aspherical + 4 ED + 1 UHR elements). Nine rounded aperture blades. The 77mm filter thread. At 690g the lens is substantial for MFT. Minimum focus distance of 28cm. Dust/splash sealed. f/1.7 constant aperture throughout zoom range — no other MFT zoom matches f/1.7. MFT image circle (20-50mm equivalent).
The constant f/1.7 aperture across the full 10-25mm zoom range is unique in the MFT system: no other zoom for any mount maintains f/1.7 across a standard-wide zoom range. On MFT's 2× crop factor, f/1.7 provides depth-of-field equivalent to approximately f/3.4 on full-frame — shallow for MFT. The Leica DG branding indicates Leica optical design collaboration with Panasonic manufacturing.
On the used market the Panasonic Leica DG Vario-Summilux 10-25mm f/1.7 is available at premium MFT zoom pricing. Condition checks: AF response, dust/splash sealing, 77mm front element for marks, zoom ring smoothness. Compatible with all Micro Four Thirds bodies.