For those interested in the Olympus ED 100-400mm + MC-20 combo (on a E-M1X), having spent a dawn-til-dusk day shooting surfers in action in Kernowfornia I can report that it's not good. All my images were shot on a tripod.
It was a changeable day regarding the light and generally cloudy overcast, so rather grey. Shots at ISO 1250 were the worst and weren't too clever at ISO 1000 either. I needed a minimum of 1/1000s to capture the fast action from the better surfers and of course the aperture could only be 'slow' settings with this particular lens. Most subjects were at long distance which also doesn't help.
Unlike Jeff, I absolutely
cannot recommend Topaz DeNoise for subjects like this - It is total rubbish! The preprogrammed
artificial intelligence simply isn't intelligent at all and makes a dog's dinner out of my typical surfing photography. I have gone back to Imageonic Noiseware which is very reliable (and also significantly faster).
So in summary, the combo performs poorly when the light is poor.
Although I didn't use it that day, the ED 40-150mm + MC-20 combo is very good indeed by comparison and was my go-to rig for surfing before I bought the Olympus 100-400mm.
In retrospect I could have taken my ED 300mm Pro F/4 + MC-20 but it was my first visit there and the flexibility of zoom is invaluable.
In futurespect (if there is such a word) I need a ED 150-400mm+1.25x Pro !!
Bude_M1X4195 by
Robin Procter, on Flickr