When you are snapping off a picture, exposing a film, uploading an album onto your Facebook, did you ever think about what makes it possible for you to do all of these?
Pretty as it is, what behind these photos is the hidden science.
How can we see the image?
The word “photography” came from “drawing with light”. The light reflected from a subject is processed by our eyes and brains to provide sense of sight. The difference in wavelengths results in a variety of colors. Jumble of light reflected from points on subject is controlled by the iris in intensity and by the stretching and compressing of lens in focus to form an image.
One characteristic of light is that its path is bent as it passes between mediums of different density, for example from air to glass. This principle is used to construct a converging lens. Such a lens takes the jumble of light from one point on the subject and converges these rays to one point of focus. The lens is moved backwards or forwards to focus, that is to create a sharp image. The image formed by a lens or pinhole is upside down.
Both the shape of the lens and the density of the glass alter the light bending power of the lens. The ‘focal length’ of a lens is a measure of its light bending power. For a simple lens the focal length is the distance between the lens and where the light rays are brought into focus.
For the same subject a shorter focal length lens produces a smaller image than a long focal length lens.
The image quality of a simple lens is poor, that is why compound lenses are used in most photographic equipment. Within a compound lens barrel there are several positive and negative lens elements, each with their own focal length. A good quality lens will produce a bright, sharply focused image without aberration.
A ‘standard’ lens is used to produce an image that is roughly equal to the human eye’s view of the scene. A standard lens has a focal length that is approximately equal to the diagonal of the film format. For example the standard lens for 35mm film is about 50mm however for the larger medium format film it is almost 80mm.
The focal length of a lens, in conjunction with the aperture setting, determines how much of the view is in focus. The amount of the view, from near to far, which is in sharp focus is called the “depth of field”. The shorter the focal length of a lens the greater the depth of field.
So next time, when someone ask you what will happen when Art meets Science, you should give them the definite answer “MAGIC!”.