On the left is the first ever in-flight image of a droplet from an agricultural "air-inclusion" nozzle. From this image, taken from a VisiSize system, not only is the droplet non-spherical, but air bubbles are visible within the water drop.
Other particle sizing techniques such as PDA or laser diffraction would mis-size the droplet without indicating they had done so - and you would never have known about the air inclusions
