Lightweight gem with one ugly blemish

Pros: 1) Extremely fast and responsive AF

2) Sharp all the way out to 300mm (600mm eq.), easily outclasses my older setup (Tamron 100-400 on Canon APS-C bodies (640mm eq.))

3) Not much more expensive than the Olympus option, but is half a stop faster, weather-sealed, and has OIS.

4) Lightweight

5) Cheap or at least as cheap as a lens in this class can get.

Cons: 1) The lens is prone to CA and purple fringing. It is quite inconsistent, it really messes up some images, while it cannot be spotted in some extreme contrasty images. I believe that this is an issue with the camera not appropriately correcting for the CA in all images.

I wanted a setup for nature photography that does not weigh more than a kilo, is weatherproof, and gives me at least 600mm 35mm eq. reach. This is the only lens that fits the criteria and it works very well on my G90.

PS.: The rubber material used for the zoom and focus ring really loves picking up dirt and lint. Also, some users have reported dirt getting in on the inside of the lens, I have no way of confirming this as I have not had it for long enough.

Original Image (Vibrance and exposure increased in post)

Crop from the previous image (shutter speed was not high enough to freeze the beak and tongue)

I have this lens, the settings I use with much success are never more than 250mm, 150-250mm f7.1 - f8, 100-150mm f6.3, adjust iso to suit shutter speed, obviously birds require higher iso=higher shutter, I mostly use the 5x5 focus point pattern or C-AF w/ tracking on my M1 mk II with good results. Hope that helps