العوامل التي يجب وضعها محل الاعتبار عند تقدير سرعة الغالق ٢-a .. كتاب آلة التصوير

For the speed of movement of people only, but the speed of the rest of the body must also be taken into account in order for the image to be sharp (Fig. 168).

On page 301, we see two tables:

The first: an approximate general statement about the speed of movement of some known bodies (estimated in kilometers per hour).

The second: converting the speed of movement of these objects into estimates of shutter speed (
Estimated in fractions of a second, with the speed of the moving object linked to the distance between it and the camera. This second schedule has been developed assuming that the object is moving horizontally relative to the axis of the lens and that the lens is of medium focal length.

(a) If the body’s motion is perpendicular to the camera, the shutter speed is multiplied by 3. For example, if the horizontal moving object requires a speed of 1/750 of a second, this body requires a shutter speed of 1/250 of a second. Camera (i.e. parallel to the optical axis of the lens).

(b) If the movement of the body is oblique (45), whether its movement is towards the camera or in the opposite direction, then multiply the shutter speed x 3/2? of what is stated in the table. For example:

If the moving body is horizontal, it needs a speed of 1/750 of a second. This same body needs a shutter speed of 1/750 X 3/2 = 1/500 of a second if its movement is tilted 45 on the lens axis.

If the lens is not of medium focal length, the following shall be observed:

(c) If a telephoto lens is used, the speed estimate will increase. For example, if we find in the previous table that the shutter speed = 1/100 of a second when photographing with a medium focal length lens, then the speed is doubled if we use a telephoto lens whose power is (x2), so it becomes 1/200 of a second. .

(d) Based on the same previous principles, the shutter speed must be changed when using a lens with a short focal length or an obtuse angle.