
The other day, psychologist
Tom Hartley tweeted "Your reflection is always half the size of the real thing - no matter how far from mirror. Hard to believe but true." and linked to
this post in which someone demonstrates this effect. I had never quite thought about it, but realised it was of course always true: the mirror is at half the distance specified in the reflection. Then I
read this post linked from the original, which reviewed an article by Lawson et al (2007) describing how people misjudge the size of objects on mirrors - specifically, they think the projection is larger than it actually is. This got me thinking about some work by Gibson on slant perception (Gibson, 1950) and then I realised that this really is an interesting topic. So I'm taking a break from the brain this week to blog about some optics instead.