Archive for March 22, 2010

Can You Trust Your Senses? Turns out you can’t.

I always wondered why sometimes, while post-processing, I would bang my head against the same wall over and over.  And over.  Too warm? Too magenta?  Is that a green cast? Wait.  Where’d it go?

And then I close my eyes for five seconds.  And when I open them, the picture on the screen might as well be a different one entirely. A completely new color cast, and now WAY over-processed.

I always assumed this was because I just sucked at post-processing.  I mean, I’m not ruling that out – I’m sure it’s a factor.  But I’ve wondered about this over time – why can I just not see objectively?  Sometimes, all it takes is someone pointing out to me that a picture has a blue cast, and I have at least a passable image within minutes.

It turns out that part of the problem is that my eyes have been lying to me.  Or more accurately, my brain has been lying to me.  Sometimes because we see what we want to see, of course.  But other times, it’s just because the way our perception of the world has evolved doesn’t line up with the ways I would prefer to sense things (say, more like a camera). In other words, sometimes I see what I don’t want to see.

An example is below – the two center squares are actually the same shade of grey, but almost no one sees it that way.

Grey Squares Illusion

Which Center Square is Darker?

Dale Purves at the Center for Cognitive Neuroscience (Duke University) has done decades of research on this sort of sensory phenomenon, and not just with vision – also with our perception of color, perspective, motion and auditory stimuli.  See more illusions here.  Layman’s summary of Purves’ research is here. Neat stuff.


Couldn’t help taking a picture of this – wish more people thought along these lines…