Hello Colin
Tell me how you focused and where, please.
Were you using some kind of table to focus on the right distance ?
You know, one of those table where you read the focus distance regarding the DOF you want based on a specified camera, aperture...
Or do you have an iPhone with that application ? That's great isn't it ?
Which lens did you use ? And camera ? How do you focus at a certain distance - say 15 meters ?
My guess: Full-frame camera; 24 mm; f/16; focus distance about 2/3 meters; low ISO; cable release; tripod; mirror locked.
I did something like this once and got some spills of water on both, myself and the camera Mind if I post it here ? It's not so good as yours, no.
How could I have forgotten ? You also used a Singh Ray filter and I correct the aperture to f/8.