We will be interested to hear if you can adjust yours eyes enough to see these ‘Magic Eye’ autostereogram pictures. The top one takes a bit of thinking about the next is enlightening and the last one is a comment on the art of stereography – Deskarati –
An autostereogram is an optical illusion of depth usually observed by allowing the eyes to focus behind the image (diverge), or, less often, in front of it (converge). These two methods are also known as wall-eyed and cross-eyed, respectively. The slight differences in vertical repetitions of figures or random dots create the illusion of depth in the2D image, just as the slight difference in perspective between one’s eyes creates the perception of depth on 3Dobjects and scenes.
According to Magic Eye, a maker of autostereograms, “most people prefer the diverging method”. However, with normal stereograms, this imposes a limit on the size of the image, since there is a limit to how much the eyes diverge; images created for the cross-eyed method can be larger. If a stereogram is viewed with the wrong method, the depth information is seen ‘reversed’; points intended to be in the background appear in the foreground and vice versa.