Computer Vision (27), Optics and Photography

The concept of the cone changes slightly, when light reflected from surfaces is taken into account. It is this light that we generally see/perceive in our surrounding, because objects reflect light and not produce light. This reflection is not the same in all the directions and hence the circular cross section of the cone will not be of uniform intensity and frequency (color). When we perceive it as a point it is the sum of all these different light rays that we are seeing.

If this sounds too complicated, just place a CD near you and try to observe a particular point where colors can be seen. From different view points you will be able to see different colors. This means that the same point on the CD is diffracting different colors. So if the aperture is big enough to accommodate all these colors, the color of the actual point will be the addition of all these. Out of focusing this point would reveal all the individual colors. One more example is the mirror, which I have already touched upon in my earlier posts. In the diagram shown above, the rectangle is the mirror and the circles are either you or your camera. Suppose you fix up a particular point on the mirror and move around it as shown in the figure you will be able to see different objects at the same selected point on the mirror. The mirror is reflecting light from different objects from the same point on it which you will be able to capture by moving around.

For all you photographers out there, bigger aperture might solve ISO problems, but depending on the aperture value you might end up getting a different color for the same pixel on your photograph. The color that your eyes see might not match the one that you get from a camera, even if you match the sensors exactly. This is because aperture also plays a role in color reproduction! Ideally you don't need a lens if the aperture of your camera is a single point, letting just a single ray of light from every point in space around it to reach the sensor. Why? You need a lens, to see a point in space as a point in the image. Normally why that is not possible without a lens is because the reflected light from objects is diverging. The lens actually does the job of converging these rays to a point, which is what focus is. When your aperture makes sure that only one ray is allowed from every point in space, there is no need to focus it! A proper image of your surrounding can be formed on the sensor without the lens. But for this to happen, your sensor should infact be very powerful to register these single rays as a visible and differentiable value.