Training neural networks for detecting slugs requires hunting down slugs in the night time and photographing them under the light of a head torch with macro lens. Fortunately, they don't move too quickly, but photography is still challenging as the macro lens is very sensitive to movement so the aperture needs to be quite large which means getting focus correct is hard. An advantage is that the background gets blurred, especially when the slugs are silhouetted somewhat. A minimum of 2,500 photos are required and each one needs to be cropped, resized to 640 x 640 pixels, renamed and then labelled. I seem to be able to do an average of about 100 a day and have done 1,000 so far.

Slugs are amazing creatures and getting this close to them is quite revealing. I think most people would think of them as being pretty gross, but on close up they are truly beautiful animals. I think I identified about 10 different species, from the large black ones to the small dappled.