So, while objects have a given nominal value, their actual value’s a function of light, and that’s compounded by the object’s surface qualities. This is a photo of a white sphere on a white tabletop in front of a white wall. But, almost nothing is white. The range of values that a given object might display is infinite. It’s all dependent on light. The primary factors are the strength of the light source, its distance from the object, and its angle and direction.