Why is it that in many instances multiple witnesses have reported simultaneous experiences with ostensible paranormal phenomena, but details of the shared experiences vary from witness to witness?
For example, one person might report seeing a free-form apparition, another, a Victorian lady, while others present may not have witnessed anything at all. If what they’re seeing is a genuine apparition, regardless if it’s an external projection of the mind (PSI), The Dead Person Hypothesis, et al - it leads one to wonder if the experiences are subject to some environmental or situational circumstances such as: ambient light, position, angle, direction, speed, etc.
You don’t have to look far for an example of how a slight change in any one of these variables can alter our perception. Changing one variable, such as viewing angle, may cause another aspect of visual stimulus not to be perceived. While viewing the line “illusion” above from a front-facing position, most people perceive somewhat nauseating black lines. Viewing the picture from another angle or different perspective allows you to see the picture in greater detail. This is known as the contrast effect.
Another example that demonstrates the contrast effect well is this “Shadow Knitted” portrait of the Mona Lisa