1. What is a T-Stop to F-Stop Calculator?

Definition: This calculator converts between F-stop (theoretical aperture) and T-stop (actual light transmission) values for camera lenses.

Purpose: It helps photographers and cinematographers understand the actual light transmission of their lenses, which affects exposure.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( T \) — T-stop (actual light transmission value)
• \( f \) — F-stop (theoretical aperture value)
• \( T_e \) — Transmission efficiency (0-1, where 1 is perfect transmission)

Explanation: The F-stop is adjusted by the inverse square root of the lens's transmission efficiency to calculate the actual light transmission (T-stop).

3. Importance of T-Stop Calculation

Details: T-stops are crucial for accurate exposure, especially in cinematography where consistent exposure across different lenses is essential.

4. Using the Calculator

Tips: Enter the F-stop value and transmission efficiency (default 0.9 for typical lenses). Transmission must be between 0 and 1.

5. Frequently Asked Questions (FAQ)

Q1: What's the difference between F-stop and T-stop?
A: F-stop is a theoretical value based on aperture size, while T-stop measures actual light transmission, accounting for lens element absorption.

Q2: What's a typical transmission efficiency value?
A: Most modern lenses have 0.9-0.95 transmission efficiency. Older or complex lenses might be lower.

Q3: Why do cinematographers prefer T-stops?
A: T-stops ensure consistent exposure when switching lenses, which is critical for maintaining visual continuity.

Q4: How much difference does this make in practice?
A: A lens with f/2.8 and 0.9 transmission would be T/2.95 - about 1/6 stop difference.

Q5: Can I calculate F-stop from T-stop?
A: Yes, rearrange the formula: \( f = T \times \sqrt{T_e} \).