What does the term 'exposure' refer to in photography?

The term 'exposure' in photography primarily refers to the amount of light that reaches the camera sensor. Exposure determines how bright or dark an image appears and is a crucial foundational concept in photography. A well-exposed image has a balanced level of light, showcasing detail in both highlights and shadows.

While the duration of the shutter being open is indeed a factor that contributes to exposure, it is only one element of the exposure triangle, which includes aperture, shutter speed, and ISO. These three components work together to control the overall exposure. Exposure, in this context, refers to the cumulative effect of these elements, meaning it encompasses more than just the shutter duration.

ISO is another aspect that affects exposure, as it determines the sensor's sensitivity to light. However, it is not the definition of exposure itself but rather a factor that influences it. Color temperature relates to the warmth or coolness of the colors in an image and is unrelated to the concept of exposure. Thus, the best definition of exposure in photography is indeed the amount of light that reaches the camera sensor, encapsulating the critical relationship between light and how it captures an image.