camera focal length

Good lens can capture good image is it true?


In this topic we will discuss about what is Lens, Structure, Characteristics and Various types of lens.

What is Lens? A piece of glass or plastic which has two opposite surface that is use to correct of vision problems, change and converges of light rays and magnification of light. It can be in different size.

camara lens


Structure of a Lens:

It is made by the small unites of glass, which is stored align inside of a plastic cylinder. We can zoom the photo by moving these elements from back to front.

Structure of a Lens


The Basic Characteristics of a Lens:

Focal Length: It is a distance, from how much far the lens can capture a photo. Its unit is millimeter (mm).That means the lens captures the photo from the distance as much as the focal length and by the low focal length the lens can capture a wide photo.

Now if there is two cameras and if one has 18 mm focal length and another has 180 mm focal length, which one will draw the subject more closer to the lens and how much times? It will be 10 X. X is the symbol of zoom. Though this is correlative. Such as if the focal length of a camera is started from 20 mm then 10 X zoom express the focal length can be change from 20 mm to 200 mm.Similarly 10X zoo of a 35 mm camera means that it is spreader to 350 mm.350 mm focal length can draw a photo more closer than 200 mm focal length.

camera focal length


Some photos of different focal length:

Some photos of different focal length

Fig(1): Captured by 10 mm Focal Length

Fig(2): Captured by 50 mm Focal length. The 50 mm focal length has a specialty that can capture the subject of the attention of eye.

Captured by 200 mm Focal length

Fig(3): Captured by 200 mm Focal length


If you want to capture a photo light must be entered through the lens. If the lens focus in a definite point the subject will be sharp from other subject. In our childhood we tried to burn something by the “Heat Glass”. That means we tried to reflect The Sun in a point. As much Heat will produce as we can make the light centralized.

Heat Glass

Heat Glass graf

The rays meet together on the plane 2.So the subjects of this plane will be clear on the photo. The subjects of plane 1 will be more unclear than other. So the focusing point of a camera will be clear most.

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