see also:

• a brief catalogue of Micro Four Thirds lenses
• Panasonic 35-100mm f/2.8 OIS X
• 3-5x standard range zoom lenses for Micro Four Thirds

• version I released May 2012, this is Panasonic's 1st weathersealed lens and its first zoom lens with constant aperture throughout the zoom range
• giving a 35mm equivalent field of view of a 24-70mm lens, it is half the size of its f/2.8 24-70mm full frame counterparts, with much faster and more accurate AF of still subjects, but of course does not offer the same ability to have narrow depth of field (DOF)
• nevertheless, the f/2.8 aperture combined with its compact size, weatherproofing, high image quality and image stabiliser means it will be an awesome travel lens in particular.
• version ii announced in Jan 2017 offers better weathersealing, and smoother aperture variance when zooming
• both lenses can support Dual Sync IS (version I needs firmware upgrade)

• 12-35mm f/2.8 = 24-70mm field of view in 35mm full frame terms
• Power OIS optical image stabiliser
• weathersealed
• 14 elements in 9 groups including 4x ASPH, UHR, UED elements
• 7 rounded blades
• internal focusing
• closest focus 0.25m = 0:0.17x macro
• 58mm filter
• 67.6 x 73.8mm
• 305g
• € 1,100

• zoom control somewhat sloppy
• MF by wire as with most lenses these days
• lens hood falls off easily
• version I allows Dual IS I with firmware update, version II allows Dual IS II

• dSLRmagazine preview - Google translation
  • very sharp throughout the frame wide open but sharpest at f/8 in the centre
  • complete absence of CA in the centre and only small amounts in corners where there is also some astigmatism
  • some vignetting wide open but this is further corrected by software
  • easily correctable minimal distortions
  • very nice bokeh
• soundimageplus - comparisons of lens sizes
• AdmiringLight review
  • sharp wide opens except wide end at closest focus and infinity in the corners
  • mild CA and distortion wide open at wide end
  • bokeh a little nervous at wide end but smoother at long end of focal lengths
  • susceptible to flare
  • but beautiful compact lens for an f/2.8 zoom, although a touch heavy for the smallest cameras
• dSLR Magazine review