I have a theory that I call the reality illusion, this is not my theory exclusively and I didn’t come up with the idea although I might be able to lay claim to the name. When you look at a painting it sometimes starts to appear real or life-like. This is different from hyper-reality or photo-realistic painting since it can appear in paintings that are clearly not photo-realistic. I’ve noticed this occasionally in my paintings but I became more aware of it recently while painting some tree fungus (sounds sooooo appealing). I wanted the foreground to stand out so I started with the background; I painted for awhile then went to make tea and when I got back the background seemed to jump off the canvas and appear life-like. It certainly wasn’t detail that made this happen because there was very little of it in this background; so, what was it that precipitated the illusion? The other thing I noticed was that the illusion wasn’t like just looking at reality. The painting seemed magically real, even though there was little attempt to render the background realistically; it was only a background. Sadly, as I continued painting and finishing the painting the illusion decreased. Clearly, I wasn’t looking at reality but I got the impression that I was looking through a window at reality; quite disconcerting. Recently the fad in photography has been to make the photo appear to be a photo of a small-scale model; this is done through reducing the depth of field to a point that it appears that the image was taken through a macro lens. I think there is some connection to what I’m describing as the reality illusion.
I have read that we form a 3-dimensional construct in our mind of how reality around us should look, if the painting vaguely matches this construct then it sometimes starts to appear real. This is not a new idea and it probably has some evolutionary advantages. If what we are seeing doesn’t fit our internal construct because of a Lion in the grass then when, or if, a lion jumps out we might have a little more time to climb the nearest tree and live to further propagate our genes. It’s certainly not obvious since we rarely actually see a lion in the grass; something that we observe simply doesn’t seem right and we watch until the lion jumps out of the grass or we just move away to feel better. Apparently, the amount of information required to formulate the 3D construct is huge, and if the flow of information slows down our brain simply starts to make it up. So, we have this 3-D construct and it needs information, and we try to match it up with what we are seeing regardless if it exactly matches or not. I suspect that what we actually see rarely matches our 3D construct but we try hard to match it up anyway, hence the illusion. If our 3D construct is close then what we are looking at starts to appear real and this may have something to do with the phenomenon of Deja-vu because if what we are seeing doesn’t exactly match our construct then we start making it up, and how better to make it up than to use past constructs.
I think that the illusion has more to do with shades and colour than it does with detail and I think this is because we are trying to match our 3D construct using our peripheral vision. https://www.sciencedaily.com/releases/2011/11/111115133233.htm
A very detailed image can certainly posses the illusion, but I don’t think detail is the ultimate cause. I think the tonal quality of the image has more to do with the illusion, and this may have quite a bit to do with the low bandwidth connection between our eyes and brain. If high bandwidth is expensive (biologically) then I understand why the connection between our eyes and brain has so little bandwidth. The trade-off is the loss of being able to differentiate between absolute shades of a colour. This example demonstrates this perfectly:
https://www.washingtonpost.com/news/wonk/wp/2015/02/27/12-fascinating-optical-illusions-show-how-color-can-trick-the-eye/?noredirect=on&utm_term=.8f42c413da8c
This is really unfortunate because I would love to be able to mix a colour that I new absolutely was the exact colour and shade of some aspect of the scene I am looking at. This ambiguity of colour and tone can be an advantage to me, as an artist; it makes it possible to induce the reality illusion with a very few strokes of my brush, unfortunately I don’t know exactly how to do this, so I’m stuck with being surprised if and when the illusion appears.
I’ve settled on a system that seems to maximise my chances of the reality illusion appearing. I decide where the darkest areas of my image resides and there I use black, but sparingly. I use white for highlights that a photographer would refer to as ‘blown out’. I treat my painting in the same way I look at a photo; dark shadows are as black as the photo paper or paint allows and highlights are as light as the paper or paint allows. These areas, both black and white, have no discernible detail so in those areas I might need to add, or make up, some detail. I do this until I just can’t think of anything else to add; hopefully the reality illusion is now in full swing.
Typically, I pick a spot (sometimes the spot picks itself) and I work on it for a half-hour or so. Every spot needs some work so it’s not hard to find one and it really doesn’t matter because If I do this enough then the reality illusion usually starts. When I’m deciding on colours I choose bright ones rather than browns or greys, but if the colour is a shadow I muddy it up a little and it seems to work.
So, the best advise I can give is to keep painting until it starts to look right. That is what I do and it generally works.
Vaguely related links
https://www.newscientist.com/article/dn9633-calculating-the-speed-of-sight
https://en.wikipedia.org/wiki/Uncanny_valley