Is the soft box based on diagonal?

No, the soft box is a kind of photographic equipment, which consists of reflective cloth, soft cloth, steel wire frame and bayonet. The flexible frame based on diagonal will make the brightness of the background change greatly, the dark part may produce shadows, and the bright part will be overexposed, which will affect the details and color expression of the background. The soft light box is based on the axis of the lamp, which can let the light shine from the front or slightly side of the subject, so that the subject can receive light more evenly, reduce the contrast between shadow and light and dark, and improve the chromaticity of the subject. So the soft box is not based on diagonal.