Lens: 3 things about lens:

1. components of lens
The photography lens tube has the cylinder form and inside it includes many pieces of lens and a aperture. Besides, the outside of its tube will have the ring for control the aperture and focal length (meters, feet). The more piece of lens the more expensive.

2. Lens and angle receivable
The SLR digital camera can switch its lens. The difference brand of camera may have the difference type of mount of lens however many difference brands of camera can use the same lens. So should be carefully when buying new lens. Besides, nowadays there are many independent brands which can produce the many type of lens in the lower price which can support many brand cameras.
Below is the focal length compare with the degree of the view receivable:


3. The focal length of lens

• Starting from a image sensor/ film until the first piece of lens. The higher focal length will give the narrow view image but the shorter will give the wider view image Also the higher focal length lens can zoom in more than the short focal length lens.

For the aperture in each lens are difference depending on the type of lens specially if you want to take the portrait picture of human , you may need the very high aperture to blur the background of your object.