The filters used were BG38 2mm + Tiffen Haze 2E, and the contaminating background light is streetlights. The white balance and color correction were taken from the profile I made for the gourd photos the other day.
The torch was the Nemo.
Procedure was to take 30 photos with the torch off using the built-in intervalometer in my Son A7s, and then repeat the process with 30 more photos while light painting with the Nemo. I then took the median of the no-torch photos to get a combined no-torch image, and took the MAXIMUM of the light-painted images to get a combined with-torch image. Then I subtracted the streetlight-only image from the streetlights+UV image in Photoshop and adjusted contrast on the results.
Final result:

Image with torch + streetlights:

Image with streetlights only:

Edited by Andy Perrin, 23 November 2020 - 03:01.