Panasonic LUMIX G X Vario Power Zoom Lens, 45-175MM, F4.0-5.6 ASPH, MIRRORLESS Micro Four Thirds, Power Optical I.S, H-PS45175K (USA Black)

I've been using this lens for the last couple of months with Olympus E-PM1 to great success. Very sharp wide open at all focal lengths even for distant objects. I have not experienced any OIS issues others have been reporting. OIS is disabled on Olympus bodies so I wouldn't know anyway. The lens is light and compact (46mm filter thread), the zooming is internal so the lens does not extend. Power zoom feature (optional) is very useful for video and also for stills. I find it very precise and superior to manual zooming. I use power zoom exclusively with this lens. The pace of zooming is control by how hard you tilt the toggle conveniently located on the left. Image quality is superb. Great color, contrast and sharpness across all focal lengths wide open, no need to stop down (it doesn't get visibly better anyway). My experience is in agreement with many reviews which said that the lens is optimized for wide open shooting. This is important because it is not a bright lens and one would have to watch the shutter speed so using apertures as large as possible is recommended.Compared to Olympus 40-150mm (I used to own one), Panasonic 45-175mm is better in every way:- Better optics. The lens is sharper especially for shooting at a distance (you would need to stop down Oly 40-150 to f8 to get acceptable corner to corner sharpness, plus Oly is not that sharp at full zoom)- Has noticeably better contrast and color- Slightly faster AF especially at full zoom but more so in lower light (tested on same body). The AF is significantly faster during video (C-AF) vs Oly 40-150mm (same E-PM1 body)- Internal zoom (IMO, all zooms should be like this, we're in 2012)- Power zooming (invaluable for video). Yet regular manual zoom is still there- Useful additional zoom range (175mm vs 150mm)- The lens is supposedly a little longer than Oly 40-150mm but it feels smaller due to much smaller filter thread (46mm vs 58mm) and feels much smaller in actual use due to internal zooming (Oly feels gigantic when extends and easily overwhelms small m43 cameras)- MUCH better build quality, rubberized zoom/MF ring, solid metal mount, made in Japan- Comes with a very nice and compact reversible hood, pinch lens cap (perfect for use with the hood) and a lens pouch

The Panasonic PZ 45-175mm f4-5.6 MFT lens (pleasantly!) surprised me. I had returned a Panasonic 45-200mm lens (that was relatively inexpensive and sharper than expected), which had, for me, an unacceptably high level of chromatic aberration problems. I hesitated buying this PZ ("power zoom") lens due to comments about a frequent problem with "double-imaging" at some shutter speeds with the lens used near 175mm, reportedly mediocre performance near infinity-focus, and the relatively higher price. When it appeared that new stock of the lens had arrived at Amazon (and with that, perhaps some "fixes" had been made), I decided to give it a try. I was attracted by its compact size (which doesn't change with either focusing or zooming), by its reportedly low level of CA, and by its having a power zoom lever (possibly useful while shooting video).What I found with the sample I received was that the image was sharp to the image corners even "wide" open at infinity-focus (and also at close-focus) throughout its zoom range, its distortion level was low, its CA level was also low, its illumination was quite even, and its resistance to flare and ghosting was high. I then checked it with many photos shot at 175mm in the potentially "offending" shutter speed range of 1/60th to 1/200th second. Only one of the photos was not sharp (but it did not show double imaging with in-focus high-contrast edges...). (BTW, this lens that I recently bought from Amazon had the firmware update version 1.1 already installed.) Next, for "fun", I tried some low-light photos at 175mm and f5.6 with the camera used hand-held for 1/10 and 1/15th second exposures at ISO 1600 with the G5. MUCH to my surprise, some of the photos were quite sharp, even when viewed at 100% - and they even looked good otherwise! (I'm still getting over this surprise!) This turned out to be a VERY good lens!I tried adding a Nikon 3T achromatic close-up lens to the front of the zoom (I needed a 46mm-to-52mm step-up adapter ring to do this), and found that this turned the 45-175mm zoom into a useful and sharp macro zoom lens! (BTW, this Nikon 3T achromat also works well on the Panasonic 14-45mm zoom lens without an adapter.) I then tried stacking the 3T and a 5T, which both have the same power) to double the power (I adapted the 5T to the front of the 3T with a 52mm-to-62mm step-up adapter ring). This also worked very well, and it resulted in very high magnification with the zoom set at 175mm.I then tried shooting video with this lens. The G5 is unusual for a camera of its type in having an on-body zoom lever for use with the couple of Panasonic "PZ" lenses available, of which this is one. These PZ lenses have zoom levers, but I found it easier to control zoom smoothness (while keeping the camera steady) if I used the zoom lever on the camera rather than using the one on the lens. The G5 also has (in its menus) additional zooming speed-rate selections making it possible to have the very slow zoom rate that I prefer to use while shooting video. But, this lens is not parfocal (it changes focus with zooming), and there have been a couple of problems resulting from this and with the lens aperture changing with zooming. I will see if I can find ways around these problems, and if successful, I will report my findings here.An additional note: a rattle can be heard as the lens is tilted. This is normal when the power is off (it is not indicative of a fault).I am VERY happy with using this lens for still photography, and I'm hoping to find ways of using it while zooming during the shooting of video.Recommended!UPDATE:I found that by using "Continuous-Focus" set to "On" in the video menus, and with the auto 23-segment AF focus pattern selected, I can get much smoother exposures with zooming while shooting video while using the on-body (G5 and G6) zoom toggle.--DR