In the retinal illumination formula, what does 'T' represent?

In the context of the retinal illumination formula, 'T' represents Trolands, which is a unit of measurement used in vision science. Trolands quantify the amount of light that reaches the retina, taking into account both the luminance of the light source and the size of the pupil. This measurement is crucial for understanding how much light is available for visual processing in various lighting conditions. Trolands provide insight into how effectively the human visual system can respond to changes in illumination, which is essential for tasks such as assessing visual acuity and contrast sensitivity under different lighting scenarios.

In contrast, time, temperature, and tension do not pertain to the concept of retinal illumination and thus are not relevant in this formula. Trolands specifically connect to the photometric science of illuminance and visual perception.