It is a concentration of the amount or resolution of light of one wavelength that makes up all color information. This is called the image sensor.
You can read more about it here: http:\/\/en.wikipedia.org\/w\/index.php?title=High_ISOLet’s watch this article together discussing what is iso in photography questions. Remember to post any questions you may have below the video.
Camera Obscura Definition
The closest forerunner of the camera was the Camera Obscura. The underlying principle behind the camera obscura (Latin for "dark chamber"), also know as " the pinhole image ," was the observation of the natural phenomenon:
Next, let us look at the brief history of the development of light-sensitive materials and early Photography before reaching the fixed image stage. Though the knowledge of light-sensitive materials existed before, there are no records preceding 1725 of any idea, even closely resembling Photography.
First Picture Ever Taken
The problem to fix the image to the medium had remained unsolved until Joseph Niepce successfully created the first Photograph using a pewter plate coated with bitumen. He later worked with Louis Daguerre to reduce the long exposure times.
Photography On Paper
Let us now look at some of the notable early works directed towards having a photographic image on paper.
The Improved Daguerreotype
The original Daguerre’s process had very slow speed, with exposure times of more than 20 minutes. This made it unsuitable for portraiture. It was only used for still life photography and landscape imagery.