Why are shadows never sharp?
In: Physics
* Size of the light source. If the light source is large enough, any object will block some light before it blocks all light. In the area where that transition lands a shadow, it will look like the shadow is fading in, which is not sharp.
* Reflections. As long as there is enough light to reflect off of objects that are near the shadow (in other words, enough light to see the surroundings), some of it will decrease the effect of the shadow. And these reflections are almost always wide and imprecise (especially if there’s any curved surfaces), so they will mess with the sharpness of shadows.
* Translucent materials. While some things are very effective at blocking light, most organic examples are at least a little translucent (especially to a strong light, such as the sun). And when that effect becomes most noticeable at the edge of an object, a little light will come through. This small effect will make shadows become less sharp.
So there are examples of sharp shadows, but they tend to counter as much of the above as possible. Small light source, dark/light absorbing surroundings, and material that is more opaque than the strength of the light source.
ETA, I want to point out that the 1st bullet point is the biggest cause (and it *is* what most of the other comments are pointing out). But the other 2 still have a minor effect.
Latest Answers