Taken with the Olympus 40-150 f/4 lens. I am a bit disappointed with it.
I think f/4 is just too slow for a 300mm equivalent tele in anything other than very bright sunlight.
Not sure it is the maximum aperture of the lens that's your problem here, I have a Nikon 300mm f/4 lens that I use on a full frame Nikon D850 with amazing results in all shorts of light. At f/4 you will have a pretty narrow DOF and you can see that with the woman's face in focus and the others features slightly blurred.
Agreed. To be honest I either didn't know, or had forgotten that there was an f/4 in that range. As I've often said, I rate my 40-150 f/2.8 as having at least the equal[1] best IQ of any lens, of any brand I've ever owned, but it IS several hundred AUD more than the f/4.
[1] At one time I wouldn't have qualified that statement, but given the IQ that I can get from my 8mm f/1.8 fisheye and 25mm f/1.2, I have to make it a tie... but of course the 40-150 is a far more flexible lens. If I had a larger sensor I may be more relaxed about it, but with M43 I will rarely buy any lens slower than f/2.8 unless it's something to fill a gap that I can't otherwise fill practically.
It's still not a bad shot, especially subject-wise; that brief frozen moment that will never come again.