I sometimes wonder what it would be like to have senses that behave differently from those we actually have. Not that I'm complaining; our senses are totally amazing as they are. But, for example, how does a dog see the world when out for a walk? As she goes down the path, all her interest is in the smells. She's "reading the newspaper." She hardly bothers to look where she's going! Visually her world is in black and white because a dog’s eyes lack the cones that allow us to split the light up into wavelength regions that our brains can interpret as colors. Probably that’s so that she can see better in lower light than we can—an advantage for predators that may be hunting at night.
For that matter, how do we know that we all perceive colors the same way or even in a similar way? Yes, we will all agree that the wavelengths around 550 nm are green (unless one of us suffers from some form of color blindness), but how can we tell if our perceptions of green are the same. Maybe my green is your red?
There’s lots of useful information in what’s sometimes called the near infrared - the wavelength range starting just after red. For one thing, vegetation reflects strongly in that region, pushing away the heat energy. This sudden jump in reflectance is called the “red edge” and its strength and position can be used to obtain indicators of plant health. For this reason, the satellites that supply information for GoogleEarth, for example, actually measure the near infrared as well. They take four simultaneous images – one in the blue, one in the green, one in the red, and one in the infrared. This is no problem for most digital sensors because they aren't as restricted in sensitivity as our eyes are. In fact, often digital cameras have filters to block out the infrared because it can cloud or haze the image.
Here is a gray scale image of the infrared. White in these images will be vegetation, not snow.
Many photographers and artists have tried to show us the world with other eyes by representing the infrared as one of the colors we usually see. The results can be quite amazing.
The image below was created by Irish photographer and artist Richard Mosse. It’s of Lac Vert in the Congo. Take a look at his powerfully dramatic images here.
|Lac Vert in the Congo by Richard Mosse|
And sometimes we can see a lot more interesting detail if we look with other eyes, such as this galaxy example.
Once you get to the longer wavelengths, you get into the thermal range and now it's not the reflection of the light that is interesting, but rather the emission of the light from the item. Really what is happening is that we are translating the different temperatures to different colors with red usually representing the hottest and blue the coolest.
Michael - Thursday