Pentax Q-S1 has a Pentax Q lens mount and currently there are 8 native lenses available for this mount.
The latest released lenses that are compatible with the Q-S1 are the Pentax 08 Wide Zoom, the Pentax 07 Mount Shield Lens and the Pentax 06 Telephoto 15-45mm.
Q-S1 also has a sensor based image stabilization system which means that all of these lenses will be stabilized when used on the Q-S1.
Since Pentax Q-S1 has a Small Sensor sensor, it has a focal length multiplier of 5.6× so you have to multiply lenses original focal length with this multiplier to find the Full Frame equivalent focal length of the lens when mounted on Q-S1.
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Pentax Q-S1 Lenses with Image Stabilization
Pentax Q-S1 Lenses with Weather Sealings