Loading Calculator...
Please wait a moment
Please wait a moment
Convert between F-stop and T-stop values for accurate light transmission measurements
T-stop Result
T/2.87
Formula: T = F / √(transmission)
| F-stop | Transmission | T-stop |
|---|---|---|
| f/1.4 | 95% | T/1.44 |
| f/2 | 95% | T/2.05 |
| f/2.8 | 95% | T/2.87 |
| f/4 | 95% | T/4.10 |
| f/5.6 | 95% | T/5.75 |
| f/8 | 95% | T/8.21 |
| f/11 | 95% | T/11.29 |
| f/16 | 95% | T/16.42 |
| f/22 | 95% | T/22.57 |
F-stop and T-stop are both measures of lens aperture, but they serve different purposes in photography and cinematography.
F-stop (f-number) is the ratio of the lens focal length to the diameter of the entrance pupil. It's a theoretical value that doesn't account for light loss within the lens.
T-stop (transmission stop) measures the actual amount of light transmitted through the lens. It accounts for light loss due to absorption and reflection within the lens elements, making it more accurate for exposure calculations.
For most photography, f-stops are sufficient. T-stops are primarily used in cinematography where exposure consistency across multiple shots and lenses is critical.
Because some light is lost passing through the lens elements, the actual light transmission is always less than the theoretical maximum. This means the T-stop number is always equal to or larger than the corresponding f-stop.
You can measure transmission by comparing light readings with and without the lens in place, or by comparing your lens to a reference lens with known T-stop values.
No, depth of field is determined by the physical aperture diameter (f-stop), not the light transmission (T-stop). T-stops only affect exposure.