Library · Formulas

1/30 rule

The oldest practical rule of stereo photography: the interaxial should be one thirtieth of the distance to the nearest object.

b = Zn / 30 C = Zn

where: b interaxial, Zn distance of the nearest object, C convergence distance

In the calculator the convergence is placed on the nearest point; the stereo window is at the nearest object and the whole scene stays behind the screen.

The sliders change the scene; the method chooses the interaxial and the convergence by its own rule. The comfort window depends on the type of the selected screen.

Origin and limits

The rule comes from traditional stereo photography and is described in Waack's book Stereo Photography. It was set up for a normal lens and 35 mm film. The maximum permissible deviation on film (the horizontal difference between the two images) is 1.2 mm for 35 mm film and 2.8 mm for 6×6 cm film (Waack).

The formula does not account for the focal length, the sensor width or the display screen. It is an approximation of the Bercovitz formula for a deviation of 1.2 mm, a focal length of about 35 mm and a scene extending to infinity; the difference between the two is around 1–2%. Outside these conditions, especially with a long lens and on a large screen, the result easily extends beyond the window.

Open in the calculator Bercovitz