Panasonic S1 has a Leica L lens mount and currently there are 29 native lenses available for this mount.
S1 also has a sensor based image stabilization system which means that all of these lenses will be stabilized when used on S1.
Since Panasonic S1 has a Full frame sensor, it has a focal length multiplier of 1x so lenses will provide their original focal length on S1.
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Panasonic S1 Lenses with Image Stabilization
Panasonic S1 Lenses with Weather Sealings