حساب عمق الميدان .. كتاب آلة التصوير

Depth of field calculator:

Our knowledge of the suprafocal distance alone is not sufficient for us to fully judge the length of the depth-of-field distance, but we must also know the distance between the lens and the middle point on which the distance is set.

And when we mention the words “depth of field”, we mean by that the area that lies in front of and behind the middle point on which the distance is set (point C in Figure 111, p. Accordingly, we find that the depth of field consists of two parts, the separating border of which is the middle point on which the distance is set in the lens, and these two parts are:

(a) Frontal depth of field: or as A is sometimes called the near depth of field, which is the foreground side closest to the lens and in which details are sharp (distance b c in fig. 111).

(b) The depth of the back field: or as it is sometimes called the depth of the far field, and it is the back side that lies behind the middle point on which the distance is set and in which the details are sharp (the distance is found in Figure 111):

Accordingly, the depth of field can be calculated if we know two dimensions from the lens:

(a) The distance between the lens and the first starting point of the depth of field
(which is the Ab dimension in Figure 111).

(B) The distance between the lens and the last point at which the depth of field ends (which is the distance shown in Figure 111).

If we wanted to know the boundaries of the region in which the details are sharp, it would be easier to subtract the first dimension from the second dimension. According to what came in Figure 111, the depth of field becomes occupied by a distance of ad - a b = b d.

If we denote the hyperfocal distance (H) by the symbol . . . . ( H )

And for the distance between the lens and the middle point on which the distance is set by the symbol (x)

For the distance of the lens and the closest point from which the depth of field begins with the symbol . . (s)

For the distance of the lens and the farthest point at which the depth of field ends with the symbol . . (B)

It is easy to calculate each distance of the “nearest point” and “farthest point” according to the following two equations:

After nearest point(s) = e x x over e + x

Farthest point (b) = e x x over e - x

Example: Assuming that the hyperfocal distance is 20 feet

And that the middle point on which the distance is set = ft. Then it can be estimated after both: the nearest point and the farthest point.