Oops, only just picked up David's comment. Thank you!
All taken with natural light. I very rarely use flash as it tends to look false no matter what you do with it. I do have ring flash available but don't like the effect. So I kind of look for fungi with nice lighting, then line up a good composition and then take the picture, always bearing in mind what the final result will look like.
I know I could lug a full lighting rig round the woods but a) there is no power, b) it is a faff and c) IMHO nothing compares to natural light anyway.
The 5D3 does exceptionally well at high ISO and looks virtually noise free even at ISO 12500 and above, so rarely need flash anyway.