X-ray images are made from a diffused source, in a way similar to the lithograms we make in the darkroom (laying the subject over the sensitive material) - but since the source is diffused, and diffused further by the subject body, the image is fuzzy. Human senses, we are taught are: touch, hearing, taste, smell and sight. But there are more - motion, sense of time, heat and one dealing with knowing where parts of our bodies are (there's a particularly disturbing condition occurring when the latter sense is confused and people feel a limb does not belong to them..) and possibly others. The heat one is most interesting - because aside from the sense of warmth, we also have some specialised thermal sensors located in our forehead and upper lip. What's interesting about these is that they're the same highly specialized type as you'd find in a pit viper - the snake that when blindfolded can still 'see' with those pits and sensors. More interesting again is that our human ones are even MORE sensitive. but the problem is they're buried too deep on most people (think skinned?) - however some people do become aware of these and can use them in the sense of being able to determine where they are spatially. Eyesight is generally thought of as the one that determines our spatial position, as well as visual perception. This is most interestingly demonstrated in some clinically blind people who have functional eyes, the parts of the brain are functional and observed to be reacting to visual stimuli, but who do not 'see' due to the brains inability or decision not to pass on processed information as 'visual perception'.. ie, they cannot judge colour. And there are physiologically blind people with lensless or damaged eyes who can not just see, but see well. We also have those sufferers of synisthesia who's sensors can trigger the wrong parts of the brain such that a colour viewed by the eye can prompt a 'smell' in the brain, or a sound can trigger a taste. And recent studies have shown happier people to be less perceptive of the world around them than angry or sad people! Hearing can also be used by us in our spatial perception of the world around us, often described by deaf people, but that isn't the same as 'seeing' in the way we think of it (ie, they cannot determine the letters on an eye chart by 'hearing' them - same (*) as above with our IR sensors - nor can they differentiate what we call colour - the different wavelengths of the visible spectrum) However animals with IR sensors like those of the pit viper should be able to 'see' letters on an eyechart with their pits attenuating the IR such that absorbent and reflective areas would appear as dark or light .. but while this would be vision, it would be limited to a monochromatic view - a red and a cyan tone of the same reflectance would appear to be the same, or monochromatically identical. Vision is interesting too in that we can interpret a 2D representation of a scene and interpret spatial relationships within that scene. I am unaware of many people being capable of interpreting any spatial relationship recorded in music. Some music can evoke (memory) experiences similar to a spatial awareness, such as echoing steps in a hallway, but to build a spatial image of the length or breadth of the hall is a different matter (some people however CAN actually determine such things :) and then we have colour blindness.. ooh! Interesting! have a peek here: http://en.wikipedia.org/wiki/Color_blindness .. particularly at the test for Tritanopia and Deuteranopia down the right hand side toward the bottom. I'm always curious how many photographers are colour blind or have impaired vision. If the numbers don't show up too well don't be concerned though if you're using an LCD monitor - if you have a CRT monitor around to view them on you may find the colours more readily revealed .. and that could leads one to make an observation about just how good or poor LCD's are at rendering colour accurately (as opposed to vividly ;)
