* Pupil Dilation: When it's dark, your pupils dilate (get bigger) to allow more light into your eyes. But this comes with a trade-off. A larger pupil also means a shallower depth of field.
* Depth of Field: Think of depth of field like the "sharpness zone" in front of and behind your point of focus. A shallow depth of field means only a very small range of distances will be in focus. When you look directly at an object in near darkness, your dilated pupils mean that the object itself might be in focus, but the area around it becomes blurry. This makes it harder to discern the object's shape and edges.
* Side Viewing: When you view an object from the side, the edges of the object become more prominent against the surrounding darkness. Your brain can better interpret those edges and define the object's shape, even if the center of the object is not perfectly in focus.
Think of it this way: Imagine a lightbulb in the distance. If you look directly at the lightbulb, you'll see a bright spot, but the rest of the scene might be blurry. If you look at the lightbulb from the side, you'll see its distinct shape against the darkness, making it easier to recognize.
