1. What is Focal Distance?

Focal distance (or focal length) is the distance between the lens and the image sensor when the subject is in focus. It determines the lens's angle of view and magnification.

2. How Does the Calculator Work?

The calculator uses the lens formula:

Where:

• \( f \) — Focal distance (meters)
• \( u \) — Object distance (meters)
• \( v \) — Image distance (meters)

Explanation: The formula relates the object distance, image distance, and focal length of a lens. It's derived from the principles of geometric optics.

3. Importance of Focal Distance Calculation

Details: Knowing the focal distance is crucial for lens design, camera setup, and understanding image formation in optical systems.

4. Using the Calculator

Tips: Enter object distance and image distance in meters. Both values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What's the difference between focal length and focal distance?
A: Focal length is an intrinsic property of the lens, while focal distance refers to the actual working distance in a specific setup.

Q2: Can this be used for both convex and concave lenses?
A: Yes, but remember that image distance is negative for virtual images formed by concave lenses.

Q3: What are typical focal lengths for camera lenses?
A: Wide-angle: <35mm, Normal: ~50mm, Telephoto: >70mm. However, this depends on sensor size.

Q4: How does focal distance affect depth of field?
A: Shorter focal lengths generally provide greater depth of field at the same aperture and focus distance.

Q5: What's the thin lens approximation?
A: This formula assumes the lens thickness is negligible compared to the object and image distances.