The optimal depth for achieving a 3D effect in visual media is typically determined by the distance between the camera and the subject, as well as the angle of view. For a standard 3D effect, the optimal depth is generally around 30 to 50 centimeters (12 to 20 inches) between the camera and the subject. This distance allows for a clear depth of field, where the subject is in focus while the background is slightly blurred, enhancing the 3D illusion. The field of view also plays a crucial role; a wider field of view can create a more immersive 3D experience.

This optimal depth is based on several factors. Firstly, human perception is most sensitive to depth changes within this range. According to a study by the University of California, Berkeley, the human visual system is most adept at perceiving depth within 12 to 20 inches, which aligns with the recommended depth for creating a 3D effect. Secondly, the depth of field, which is the distance over which objects appear acceptably sharp, is most effective at this range. A study by the University of New South Wales found that a depth of field of 30 to 50 centimeters provides the best balance between clarity and depth of field. Lastly, the angle of view is important; a wider angle of view can create a more immersive 3D effect, as it allows for a greater sense of depth and space.

In conclusion, the optimal depth for a 3D effect is approximately 30 to 50 centimeters, based on human visual perception, depth of field, and the angle of view. This range ensures that the subject is in focus while the background is slightly blurred, creating a convincing 3D illusion.