Stefan
Also in the photos you posted as my label (photo #1) Nakayama was photographed at 2 mircometers as were photos Escher photos #3) & #4).

On the other hand, photo #2) was photographed at (and is labeled as 1um) 1 micrometer which accounts for the particles appearing to be the same size as in photo #1 while in reality, if I am not mistaken they are 1/2 the size as the particles of grit in photo #1. Alx