Aperture Area Calculator
Calculate aperture area, diameter, f-number, and light-gathering power for optical systems
Calculate Aperture Properties
Diameter of the optical aperture
Distance from lens to focal point
Ratio of focal length to aperture diameter
Common F-Number Presets:
Calculation Results
Formulas: A = π(D/2)² = π(f/(2×n))² | n = f/D
• A = π × (50.0/2)² = 1963.5 mm²
Example Calculation
Camera Lens Example
Given: 85mm f/1.8 portrait lens
Find: Aperture area and light-gathering power
Solution
1. Calculate diameter: D = f/n = 85mm / 1.8 = 47.2mm
2. Calculate area: A = π(D/2)² = π(47.2/2)² = 1750.8 mm²
3. Light gathering vs human eye: 1750.8 / 38.5 = 45.5×
Result: 1751 mm² area, 45× more light than human eye
Aperture Concepts
Applications
Understanding Aperture Area
What is Aperture Area?
Aperture area is the cross-sectional area of the opening through which light enters an optical system. It directly determines the light-gathering power of telescopes, cameras, and other optical instruments. Larger apertures collect more light, enabling better performance in low-light conditions.
Key Relationships
- •A = π(D/2)² - Area from diameter
- •A = π(f/(2n))² - Area from focal length and f-number
- •n = f/D - F-number relationship
- •Light gathering ∝ Area ∝ D²
Applications & Examples
A = π(D/2)²
- A: Aperture area (mm², cm², in²)
- D: Aperture diameter (mm, cm, in)
- f: Focal length (mm, cm, in)
- n: F-number (dimensionless)
Photography Tip: Each full f-stop change (e.g., f/2.8 to f/4) halves or doubles the aperture area and light gathering power.
Astronomy Note: Light-gathering power increases with the square of diameter. A 200mm telescope gathers 4× more light than a 100mm telescope.