How Camera Works

Every camera is essentially a lightproof box, with some method of letting in just a small amount of light at just the right time. The camera start works with:

1.         Once the light is in the box, it forms an image (like in the camera obscura), causes a chemical reaction on photographic film (like in the Brownie camera), or energizes a photocell (like in a digital camera).

2.         when you snap a picture. (You can see right away that a camera obscura wouldn’t do you much good for this kind of picture!)

3.         When press the button on an SLR camera, the mirror flips up exposing the film to the light coming through the lens. One kind of camera which can be either a digital camera or a traditional film camera is called asingle-lens reflex (SLR) camera. In this camera, there is only a single set of lenses for both viewing and photographing an image.

- First, light bouncing off the picture passes into the camera, through a set of lenses, and onto 
a mirror.

– the light bounces up and into a funny-shaped piece of glass called a pentaprism (penta means five, and the pentaprism has, you guessed it, five sides).

-Once light enters the pentaprism, it bounces around in a complicated way until it passes through the eyepiece and enters your eye.

4.         When you press the button on the camera, the mirror flips up out of the way. Instead of bouncing into the pentaprism, light from the picture passes directly to the back of the camera. There, it either hits photographic film and starts a chemical reaction, or else it impacts an array of light-sensitive cells that release a tiny electric charge in each activated cell.

SLRs are not the only camera type.

Many of us use direct vision compact cameras or just “compacts”. In this camera, the lens for viewing is separate from the lens we use to take photographs. Because of the two sets of lenses, compacts don’t need a pentaprism or a hinged mirror, making them smaller and lighter than the SLRs.

Reference:

http://www.yesmag.ca/how_work/camera.html

2. human eye vs camera : similarities and difeferences.

Human eye	Camera
Similarities
Both eye and a camera can adjust quantity of light entering. Both focus an inverted image onto light-sensitive surface.
Differences
Limitation of resolution	In the eye, this is limited by the density of rods and cones on the retina and fovea.	Film resolution is limited by chemical grains on the film substrate.
Contrast	Eye is better at determining contrast or differences between light and dark.	Film or digital sensor can adapt to different levels of light just as with human night vision and daylight vision.
Colour	The adaptation of human eye towards light and colour intensity is instantaneous.	The adaptations are more computationally intensive in the digital imaging functions.
Accuracy of focusing	Less accurate than camera	Very high
Image sensor	Far better than camera	Moderate
Time lapse	Human eye can only use the light visible at one instant	A camera lens can create a brighter picture with less light.

References:

1.       http://www.ehow.com/facts_5989925_human-eye-vs_-camera.html

2.       http://lockergnome.net/questions/166986/the-camera-vs-the-human-eye

3.       http://www.rags-int-inc.com/PhotoTechStuff/CameraEye/

4.       http://www.pixiq.com/article/eyes-vs-cameras