So, full disclosure, this is not my image
It was taken by Rory Low and posted on the British Mycological Society group on Facebook.
https://www.facebook.com/rory.low.16/Why am I posting someone else's image?
Well, I was very surprised at:
- how close he's able to focus using his iPhone
- the apparently quite good quality of the image
Note - he says that he finds using a headtorch makes a big differences when working this close & low