The question now is, how come light rays travel in straight horizontal lines when dealing with mirrors, but suddenly start crossing each other when going though a pinhole or a lens? — Hachem
Each point in space will probably only be able to reflect light in one direction, or at least in a limited number of directions. — Hachem
"Did you know that the size of the diaphragm has no influence whatsoever on the field of view?"
"instead of thinking of rays that somehow know whether they will be dealing with mirrors or pinholes/lenses, "
"Another problem with aperture is that the extra light that gets through the lens does not necessarily come from the objects depicted in the image. Think of the tapetum lucidum, the shining layer at the back of a cat's eyes that makes them shine in the dark. It reflects light back onto the retina and makes it possible for the cat to see better in the dark. It is apparently the same principle as a larger iris, a way of letting more light through. But is this extra light reflected off the objects we are seeing, or simply ambient light with no specific target?"
"If that light came from the objects themselves we would be confronted with the previous problem: larger objects would be more hindered by smaller apertures than smaller objects, and should therefore appear relatively darker. "
"Here is the problem: the image shown by the projector does not come from the light, even if we assume that once the light goes through the slide it gets colored just like the slide before it finally hits the screen. "
"In the case of a camera or our eye, we would have to accept the idea that the image is somewhere on or in the lens, and that light from the outside shines through it and projects it on our retina or the sensor area. But how did the image get in the lens if not carried by the light rays?
Okay, maybe it was carried by the light rays reflected off the objects, and once it was in the lens extra light shone through it?"
What extra light that gets through the lens doesn't come from objects depicted in the image? With a less than ideal lens, like a real lens, you get lens flare and whatnot. But the phenomenon in a cat's eye you are talking about is just light, focused as usual by lens and iris, that happens to miss the rods and cones striking material slightly beyond the rods and cones and reflecting back toward the rods and cones, where it has a second chance of being detected. — oysteroid
Move your head much lower and you might see a point of blue from the sky, since you'll be looking up through the hole. The important thing here is to see that any given point in space is only receiving light from one point in the scene, found by tracing a line from that point in the room to that point in the scene. — oysteroid
What happens with a projector is as follows. Light comes from a lamp and is sent through a condenser lens and then passes through the film. Let's stop here for a moment. What is happening at the film is once again nothing but restriction of the light. The film is basically casting a shadow. The light coming through the slide does not "get colored". The light before the slide is already composed of photons of many different wavelengths — oysteroid
Light that "happens to miss the rods and cones" is reused, enhancing the sensibility of the eye cells. You will agree with me that where they get reused is, from our point of view, quite random. The point is, light that is not directly reflected by an object can be used to brighten the image of this object.
There is an old technique in analogue photography called pre-flashing. It consists in exposing very briefly the film to unfocused white light, and this has as a consequence that the emulsion as it were awakens and stands to attention. The real story concerns the number of ions and electrons that are activated by this pre-flash, and which get added to those activated by the subsequent shot, but details are unimportant.
What is important is the fact that light that does not come from or is not reflected off an object contributes to its brightness and visibility.
That is also the main point I am trying to make when I argue that when we are looking at an object through a telescope, we are seeing the object there where it is, at the moment it is there. That is impossible according to Optics which says that the light reflected or emanating from the object must reach our eyes first. I beg to differ. Telescopes would be of no use whatsoever.
One of the most obvious but still unexplained phenomenon is that objects appear smaller with distance.
I am afraid I don't follow your thinking on instant light propagation at all and I don't see how it relates to cat eyes and pre-exposure of film. There is a mountain of evidence for the fact that it takes time for light to travel and that when we see distant objects, we are seeing how they were in the past. We can actually see this — oysteroid
This is easy to explain. Once again, just consider the geometry. This says all that needs to be said on the matte — oysteroid
Why would telescopes have no use if they don't allow us to see things as they presently are? It is much better to see Pluto as it was hours ago than to not see it at all! Surely it is good to be able hear someone from across the room even though it takes time for the waves in the air to reach my ear! — oysteroid
The larger the aperture, the less the light on any given point on the screen is restricted to just one part of the scene. So, being less restricted, there is more light, but less sharpness. — oysteroid
The larger the aperture, the less the light on any given point on the screen is restricted to just one part of the scene. So, being less restricted, there is more light, but less sharpness. — oysteroid
Now, just move your head around while looking through the hole. If the hole is small enough, you only see a small point of color. Suppose your head is in such a position that you see a point of red on the door of a parked car. Move your head much lower and you might see a point of blue from the sky, — oysteroid
Your idea is ambient light coming from all directions, and rays reflected by the objects, also coming from all directions, contribute to the sharpness of the picture.
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