> They are only "essential" properties according to the limitations of your particular perceptual system. To a bee that can see UV light, a stick bug may look e

> They are only "essential" properties according to the limitations of your particular perceptual system. To a bee that can see UV light, a stick bug may look entirely different from an actual stick. An animal that hunts by scent would find them clearly distinct. This is a very confused statement. Fist, since we are talking about image recognition we are - by definition - talking about vision in the spectrum that can be captured by a digital camera and encoded in a typical image format. Second, there definitely is such a thing as essential property. It is a matter of correlation with reality, as well as internal consistency. For example, plants are green and have leaves because of the way they use sunlight. So permuting color of all leaves in the picture is fundamentally different from permuting luminosity of some random pixels.