Lens speed

The lens speed is depend on a size of aperture (f number or f/value) by f/value can calculate from ratio of focal length and aperture's dimension. For example, aperture size is 35mm and focal length is 50 so the f/value is 50/35 = 1.4 and the lens speed is 1.4 also.
The lens speed will show on the font of lens as:

High dimension of aperture this make f/value is smaller and more light go inside the lens so it is higher lens speed. Compare between f=1.2 and f=2.8 we can said that f =1.2 is more speed than f =2.8

Lens type: Reflex lens

This can be considered as one kind of telephoto lens by it has 2 times of light reflex in inside the lens tube so the focal length is increase even if the length of lens is shorter.
The diagram shows the light reflex in reflex lens.

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Lens type: Zoom lens

Zoom lens brand: Pentax

This type of lens is very popular because it can change the focal length so it is very comfortible for users. This lens need a very complex designed for focusing point in every focal length. Generally this lens will have the 2 values of widest aperture between lowest focal length and highest length due to the light is decrease when we zoom from low length to high length. However, It can produce the zoom lens that can give the constantly aperture in each focal length but it will be very expensive because of it need the special equipment and special technique for contrast and color editing. Besides, the way to change the focal length of lens can be done by twist the ring of lens or by pull out/in.

The problem of zoom lens is can not have very wide aperture so it needs to use the low speed of shutter also this hard for hold the camera by ourselves. In the zoom lens which is can give a wide aperture as single lens will have a very high cost.

The zoom lens can give the magic of picture , let’s try to change the focal length while press the
shutter, do not forget to set the low speed shutter at 1 ,2, etc.

Lens type: Telephoto lens

This type of lens will have the angle view only 2-28 degree and very low depth of field but can show picture of object as closer even it is placed in long distance.

The focal length of these type of lens will count from the normal lens such as 85mm, 100mm, 135mm, 180mm. If it has very long focal length we will call “Super telephoto lens” such as 600mm, 800mm, 1200mm, etc. This type of lens is very suitable for the photographer who can not closely access to the objects for example, take the photo of wild animal or sport.
Telephoto can give the outstanding of your object in the picture because it can reduce the perspective of the image. Some people tell that should use this lens for candid picture with empty background.
The suggestion of using telephoto is do not use the lower speed of shutter than 1/focal length for example, if you use lens 135mm , you should use speed of shutter equal or higher than 1/125 however, if it need to use the lower speed you should use the tripod.

In general we use the telephoto lens for take picture with give more perspective and less distortion.

If you use wide lens take the picture in close distance will give more distortion as:

Lens type: Fisheye lens

One type of wide angle lens that have the angle can be 180 degree and also give very distortion of the picture. Below is the picture from fisheye lens as you see it give very distortion but funny!

Lens type: Wide lens

The wide lens or the short focal length lens will increase the perspective of the image and give the wider angle view such as lens 18 mm. can have 94 degree of angle. The wider angle lens can make the more distortion by the vertical line (90 degree) will slightly bend into the centre of the picture. However the high quality of wide lens can reduce the problem of distortion and also the more quality the more price. We should use the wide lens with the view picture because it give the more depth of field. Also we can take the macro by the wide lens but it will give the wider background.

The new style of these type of lens will be designed in INVERTED TELEPHOTO that make the higher distance from lens to image sensor/film but it still can give the same focal length. Besides, it has the Shift lens or Perspective Control Lens that designed for architecture use so it can solve the problem of distortion (the vertical line (90 degree) will not slightly bend into the centre of the picture). Here is picture of shift lens: And here is compare between normal and shift lens:

Left: from Shift lens and right: from normal lens

Lens type: Standard/Normal lens

Standard lens can be called Normal lens. It can give the image closest with the image which human’s eyes given so its name is Normal lens. The focal length of this lens are 50-55 mm. can be used for general photography and give the average depth of field. Normally, this type of lens will be the kit lens (sold with the camera).

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.

Introduction to Lens

• Lens is the eyes of the camera because what you will see from a camera is depend on what is the lens see. :)
• Lens is the very important of your camera. It is a transparent which is made from glass or plastic, it used to a tool for creating the image on film or image sensor. Lens can be made of a single lens or set of lens so we can apply them in many styles.
  All the glass that makes for lens are very detailed a good lens will can speed up for light reflex and give a good quality of contrast, color and distortion. Besides, lens is coated by a special liquid that can reduce the reflection of external light so can produce the satisfied image.

Many of the lenses used for photography are created on specifications that are almost identical to the prescription lenses that are used in glasses. These specifications are normally instilled in lenses that are totally separate from the camera that they will be attached to but the specifications will have to take into account the lenses that are on the camera too.

There are a variety of lenses that an amateur photographer can use to learn the basics of photography, and there are various styles to camera lenses that would typically be chosen by a professional photographer to use during the course of a business day. The professional photographer will have several cameras in his arsenal that are pre-set for the photographic poses that he will use in his photographs while he is at work.

There are various environments that will affect the quality of the photographs taken, and the lenses chosen for inside a photo studio will be dramatically different from those chosen for a photo shoot in bright sunshine, or in the dark recesses of a photo opportunity that might present itself at the entrance to a nightclub or other nightspot frequented by celebrities.

Most often, a professional photographer will consider zoom lenses used for photography at a football game but the photographer will have to make a choice on whether they want to use a camera with a wide-zoom lens to capture all of the action on the field, or if the photographer needs to concentrate on the up close and personal shots that tourist are very fond of that show the facial features of the person in a whole new light.

Some scientists consider the telephoto lenses used for photography of images that are millions of miles away. The lens mounted on a telescope might weigh more than 3,000 pounds but that lens is also capable of capturing images that might come from the surface of the moon or the newly downgraded planet called Pluto. The scientific uses for zoom lenses may also help space explorers to view damage that has occurred outside one of the space vehicles while in outer space.

Many of the cameras that are used for recreational photographs will typically have zoom lenses installed, but offer no opportunity to adjust the setting on the lenses to gain a better view of the intended subject. Many of these camera lenses will feature an automatic focus and offer the amateur photographer a photographic tool that is easy to maintain and affordable at the same time.

Some professional photographers will chose a different lens for the photographs that will be developed for portraits. Other lenses in his arsenal might allow the professional photographer to apply a color enhancement to the skin of a subject or to add brightness and clarity to landscape backgrounds that are most commonly found in a photographer's studio. Every camera lens will allow the professional photographer to approach his work with a different perspective.

Reference: James Brown From Article Explosion