The half-translucent section diffuses and softens the light from the strobe. Using the diffuser gives softer, more evenly exposed images. The diffuser will also help reduce effects of overexposed images or when strong light produces shade/shadow in the image. Easy and Versatile Slave TTL. As the YS-03 has been designed to mimic the light intensity of the camera's built-in flash, it is not necessary to manually adjust output. The YS-03 is compatible with any camera with a pre-flash and that has a TTL flash exposure function, regardless of make. The YS-03 has been designed for any underwater photographer to use and is easy to understand. The only control is the rotary power switch and by simply turning the switch from OFF to TTL you can take beautiful images.