Why do transition lenses go dark in sunlight when you’re outside but not when you’re in a brightly lit room?

Question

Why do transition lenses go dark in sunlight when you’re outside but not when you’re in a brightly lit room?

In: 12

Answer 1

Your eyes do not have a linear sense of brightness. In other words, a room that seems twice as bright to you is not actually twice as bright.

Instead, your eyes/brain have a logarithmic sense of brightness. In near-darkness, we can detect even very small changes in brightness. A candle flame might seem twice as bright as a smaller candle next to it, but not be actually twice as bright by scientific measurement.

But in bright light, our eyes cannot detect small changes in brightness anymore. For example, a brightly lit sunny day can be literally 2,000 times brighter than a very brightly lit room, but does not feel that way to our eyes.

But you better believe a pair of transition lenses can tell the difference.