CompuServe Messages

Lenzfx

    27-Dec-94 04:32:55
Sb: #143742-Lenzfx
Fm: Aaron W. Ostler 74672,127
To: Scott Roberts 75604,1712
Scott, I don't mean to swamp you, but you inquired. <<The image reflected doesn't gain any special properties because of the location of the mirror. The reflection's state of focus is solely dependant on a simple equation: the distance from the viewer to the mirror + the distance from the mirror to the reflected item.>> I think anyone who's looked through a telescope or a pair of binoculars would argue the first point. And as for the second, you are correctly stating the equation for the distance traveled by a ray of light, but this has absolutely nothing to do with how a camera or our eye perceives the focal qualities of a scene. For example, A —————–C \ / \ / \ / \ / \/ B \ \ \ D A is the viewer or camera, C is an object, B is a reflective object, and D is an arbitrary point so that CB = BD. When viewing the scene from A, light travels from C to A by AC and from C to A by CB, BA by reflection from B. Now it is your contention that since focus is based on the additive property of the entire length of the rays path, we should be able to bring the reflection of C on object B into focus by placing the focal point at D. To back up a little bit, lets assume that object B is not perfectly reflective. Meaning that object B will add, say 50% of its light reactive qualities to the perceived reflection, as is the case with a polished desk top. Given our focal point at D, your theory of focal perception, and object B adding its qualities to the reflection, what we'd have is a reflection that is in perfect focus (since AD is our focal range) superimposed upon a surface which is out of focus (since AB is not our focal range). I'm trying to imagine how this would look but I'm absolutely certain that it's nothing I've EVER seen in real life. It's obvious that you've investigated quite seriously into occular physics and I think you'd find it interesting to read and learn how those theories that have been around for hundreds of years are put into practical use through ray-tracing and other fields of computer imaging. Aaron