Try placing bright light on top (to get rid of reflection). A mirror on the side gor him to flare at. Take a side view picture without blits/flash.
By the way he looks, I don't think he is delta. He should be HM. But he is not show quality as both color and form must conform with IBC standards.
Fins must be equal lengths, all 3 fins must meet/slightly over lap. Dorsal and anal leaning forward.
As a bicolor, his fins should be totally one color and body different color. No color bleed on either of them.
If fins have color bands (butterfly), the color bands should equal (50%) and should be the same on ALL fins.
A solid color means, the fish is totally one color - including ventrals and preferably pectorals too. For base colors, the head is allowed to be black/dark since it's not caused by color genes. But masking should merit points.