To find the scale factor, we start with the given scale of the drawing: \( 8 \) millimeters = \( 4 \) meters.
First, convert the meters to the same unit as the millimeters. Since \( 1 \) meter = \( 1000 \) millimeters, we convert \( 4 \) meters to millimeters:
\[ 4 \text{ meters} = 4 \times 1000 \text{ mm} = 4000 \text{ mm} \]
Now we can express the scale in terms of millimeters:
\[ 8 \text{ mm} = 4000 \text{ mm} \]
Next, we find the scale factor by simplifying the ratio of the drawing measurements to the actual measurements:
\[ \text{Scale Factor} = \frac{8 \text{ mm}}{4000 \text{ mm}} = \frac{8}{4000} \]
Now we simplify the fraction \( \frac{8}{4000} \). We can divide both the numerator and the denominator by \( 8 \):
\[ \frac{8 \div 8}{4000 \div 8} = \frac{1}{500} \]
Thus, the scale factor of the drawing is:
\[ \boxed{\frac{1}{500}} \]