Technical Support wrote:
When the deflector is is installed on a beauty dish, there is an area where light is blocked. As you back out, the larger area of light around the blocker starts to spread filling in the shaded area. The tighter the grid, the more it will need to be moved back.
Which Beauty Dish and which grid are you using?
Hi I have run a few tests. Yes , situation improve by backing the deflector. Yet photographing directly into the BD you can clearly see a quite amazing circular are just outside the deflector that is lighter in tone (less intense) This area stops when the beauty dish changes its shape i.e when th bottom start to close to make the shape it has. By projecting on a white wall and measuring with a sekonic this lighter area is a 1/3 of a stop lower. When I use the 30 grid the situation is more dramatic. Even if I back the deflector almost to the end of its pole, the darker spot is 2/3 of a stop lower with respect to the outer light ring projected outside. Is this thing bother just me? I haven t heard of any other BD having this same beahaviour. Actiually using a gridded bD into a face in a close up results in quite evident underesposure. Can anyone suggest a solution?