Why is the focal length of a normal digital camera expressed in multiples, while the DSLR is express

In the same way, there are millimeters next to your digital camera lens, the largest divided by the smallest is the zoom factor, which is actually a meaning, a different way of expression.

For example, Sony T20 is 3x zoom, and there is one next to the lens, which means 3x zoom.

There is also a point that a digital camera is a head, but a DSLR camera can have multiple head conversions, not a specific one, so it is easier to represent it in millimeters.

Focal lengths are all expressed in millimeters. Expressed in magnification, that's the zoom factor.

You will have the impression that most of the ordinary digital cameras are zoom, so the zoom factor is placed in a very conspicuous place; On the other hand, many SLRs are non-focus-free lenses, so there is no magnification only focal length.

The difference between image distance and focal length is as follows: different distance properties, different convex lenses, and different fixities.

First, the nature of the distance is different.

1. Image distance: the distance between the image and the plane mirror (or the optical center of the lens).

2. Focal length: refers to the distance from the center of the lens to the focal point of light concentration when the parallel light is incidence.

Second, the convex lens is different.

1. Image distance: The larger the object distance, the smaller the image distance, but the image distance is always greater than the focal length.

2. Focal length: convex lens imaging, the focal length is obtained through the focal point.

Digital cameras. The focal length identified on .

24mm-120mm, refers to the focal length range of the lens, which is also known as the "focal length".

Specifically, the focal length range of this lens is:

The shortest focal length is 24mm.

The longest focal length is 120mm.

As for this length (in fact, it should refer to the focal length of the lens, it is not accurate to say the length) refers to the distance from **to**, this is a physics problem......Specifically, focal length refers to the distance from the center of the lens to the focal point of light concentration when collimated light is incidence.

The focal point, which is easy to determine, is the position of the camera's image sensor ......As for the lens center of gravity of the lens, it needs to be analyzed according to the specific situation of the lens......This is because a lens is not a single lens, but a ...... made up of a group of lenses consisting of multiple lensesAs a result of the combined action of these lenses, the lens center ...... of this lens is formed at a certain locationThe distance from this position to the sensor is the focal length of the lens.

Since this lens is a zoom lens, its focal length is variable, and the distance between the optical center of the lens and the image sensor is also the focal length of the lens.

The change of the ......

Focal length, also known as focal length, is a measure of the concentration or divergence of light in an optical system, and refers to the distance from the center of the lens to the focal point where the light is concentrated. It is also the distance from the optical center of the lens to the imaging plane such as the tintle or CCD or CMOS in a camera.

In a word, it is the distance from the center of the lens to the sensor.

Cameras generally indicate equivalent focal lengths. That is, the focal path of a full-frame camera is comparable.

The actual focal length is related to the size of the sensor. Example 43 system, 12mm equivalent to 24mm in full width

This is equivalent to the focal length of a convex lens, 50mm is the focal length of the human eye, it can shoot the proportional effect that people can see visually, 20mm is probably similar to a fisheye lens, it can shoot a larger range, 120 is a long focal length, even if.

The longer the focal length, the closer the shooting distance, and the brighter the aperture, the stronger the bokeh effect.

Background blur, which is loved and frequently used in photography, is closely related to the focal length of the lens used, the brightness of the aperture (aperture value), and the shooting distance (the distance from the camera to the subject). When the aperture value of the lens used is constant, the longer the focal length, the more likely it is to blur the background. Of course, if the focal length is the same, the lens with a brighter aperture is more likely to produce a bokeh effect.

In addition, the degree of background blur varies depending on the shooting distance. The shorter the shooting distance and the closer you shoot, the greater the bokeh effect. Therefore, if you want to achieve a large bokeh effect, you should choose a lens with a short near-range shooting distance, a brighter aperture, and a longer focal length.

However, when taking photographs, the focal length of the lens is determined first, and the shooting distance is fixed after the composition is completed, so it is necessary to grasp the relationship between the focal length of the lens and the shooting distance while mastering the basic principle of bokeh that is longer, closer, and brighter.

This formula is useful for optical research, but it is not very useful for photographers, and the salesperson probably said that if the subject is 78 meters away, the background cannot be blurred, which is the depth of field

1. Under the same aperture, the focal length is short, the depth of field range is large, and the focal length is long, and the depth of field range is small.

2. The focal length is short, the shooting range is wide, and the focal length is long, and the shooting range is narrow.

A lens with a mm focal length can shine at sunrise.

The longer the focal length, the closer the shooting distance.

What is the focal length range of a digital camera, and its role is specifically introduced.

The focal length range refers to the span of the largest and most small focal length of the zoom lens. Nowadays, most digital cameras use zoom lenses, for example, the focal length of a camera lens is equivalent to 38 114mm of a 35mm camera (the physical focal length may only be a few millimeters to a dozen millimeters), and 38 114 is its focal length range. The "equivalent" in focal length is due to the small imaging area of digital cameras and the small angle of view, so for the sake of habit, the focal length of a 35mm camera is equivalent to that of a 35mm camera.

The larger the focal length range, the more convenient it is to use, but the lens with high quality requirements, the lens with low quality, the focal length range is large, and the imaging preparation is not good. Hello, I hope this can help you. <>

The high school physics "Small Aperture Imaging Problem" talks about the focal length from the center of the lens to the focal point of the light concentration.

For a camera, focal length is simply the distance from the center of the lens to the bottom lens.

The 135 camera uses 135 film, and the size of the 135 film is 36*The film format of the camera is 36 mm wide x 24 mm high, and the total height of the square perforations is 35 mm. That's why it's also called a 35mm camera. 135 refers to the number of the film and has no practical meaning.

The 120 camera uses 120 film, which uses a larger film area of about 6 centimeters in width, and the different types of 120 cameras use different lengths of film, including 6, 7, 9, 12 and even 17 centimeters.

Focal length, in fact, simply put, is the camera focus, blurry or clear.

Then mm, for example, I buy a DSLR, the lens is marked 18-55mm, which is the original lens, which represents the focal length, that is, how far and how clear it can be pulled. And then I don't know what to say.

As for this, it is not the length of the length, but the distance of the pull

It depends on what you shoot, you can shoot a wide angle if it's small, and you can shoot a close-up if it's large.

The CCD of a digital camera is smaller than the negative of a traditional film camera, so that the lens of the same focal length is used digitally, which actually increases the focal length of the lens, and the equivalent focal length refers to the lens focal length equivalent to the traditional 135 camera, and the actual distance is the lens focal length of the digital camera, which is converted to the coefficient multiplied by the Canon camera and the coefficient of Nikon.

The actual focal length is a parameter of a particular camera, and since there are various CCD sizes at present, the actual focal length is also varied. In this way, it is very inconvenient. For this reason, the actual focal length of various cameras is converted to the focal length of a 35mm camera, which is called the equivalent focal length, so that cameras of different CCD sizes can communicate and compare on the basis of a platform.

When the same focal length lens is placed on a camera of different CCD sizes, the angle of view is different. For example, the angle of view of 50 is 46 degrees when mounted on full-frame, and the angle of view is in degrees when mounted on APS-C format, and the angle of view of degrees is equivalent to the angle of view of a 75mm focal length lens mounted on a full-frame camera. In order to facilitate comparison, the camera manufacturer proposed the concept of equivalent focal length, but the actual focal length did not change, only the angle of view changed, and the effect was equal to the cut piece.

This question is still a more professional one.