When taking pictures, the object gets bigger, the distance gets closer, and the focal length gets bi

If the distance is not changed, the focal length is long, and the focal length is small. If you don't move the zoom lens, the focal length won't change. It seems that you need to understand the concept of focal length of a lens.

What does lens focal length mean? What is a standard lens? What is a Telephoto Lens?

What is a short throw lens? What is a zoom lens?

Focal length is an important parameter of the optical lens, when a beam of parallel light passes through the convex lens along the principal axis direction of the convex lens, it will converge into a point on the main axis on the other side of the convex lens, which is called the focal point, and the distance from the focal point to the optical center of the convex lens is called the focal length of the convex lens. A photographic lens, like a convex lens, also has standard, long, and short focal lengths. The length of the focal length = the diagonal of the imaging frame is called the standard lens of the 135 camera, the diagonal of the frame of the 135 camera is 58mm, and the diagonal of the frame of the 120 camera is 75mm, and the standard lens is 75mm; Those that are longer than the standard lens are called long focal length lenses, and those that are shorter than the standard lens are called short focal length lenses.

Lenses with different focal lengths have different styling characteristics, such as short focal length lenses have the characteristics of wide viewing angle, large depth of field, large perspective effect, and small image. These characteristics are used in the creation of the means of modeling. A lens with variable focal length is called a zoom lens, and the ratio of the shortest focal length to the longest focal length is called the zoom factor of a zoom lens.

The larger the zoom factor, the more significant the change in the field at the same shooting distance. From the perspective of focal length, lenses with wide angles and large zoom multiples are the best, mainly used in professional photography, and the cost is also the most expensive.

Focal length is a physical constant, which has nothing to do with the distance of the subject. It's like the speed of a car and the age of the driver.

If the lens is in focus, then the focal length does not change. No matter how big the object is or how close it is.

Focal length is the distance from your camera to the focal point.

The larger the focal length of the camera, the smaller the field of view.

Focal length is a measure of the concentration or divergence of light in an optical system, which refers to the distance from the center of the lens to the focal point of light concentration when collimated light is incidentified. Optical systems with short focal lengths have a better ability to concentrate light than those with long focal lengths. In simple terms, focal length is the distance between the focal point and the center point of the mask.

In the camera, the focal length f and image distance < 2f to image.

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 of the light. 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. Optical systems with short focal lengths have a better ability to concentrate light than those with long focal lengths.

The concept of focal length:

The metal barrel of a camera or projector houses a set of lenses with curved sides or sides to form a composite lens. The light emitted from different parts of the object, after passing through the lens, is focused on a point of the negative, so that the image has a clear outline and a real texture, and this point is called focus. The focal length is the distance from the middle point of the lens to the point where the light can be clearly focused.

Because when we take pictures, the distance between the object being photographed and the camera (lens) is not always the same, for example, when we take a picture of someone, sometimes, if we want to take a picture of the whole body, we are far away, and if we take a picture of the half body, we are closer. In other words, the image distance is not always fixed, so in order to get a clear image, it is necessary to change the distance from the film to the center of the lens according to the distance of the object, and this change process is what we usually call "focusing".

The relationship between object distance, image distance, and focal length is as follows:

1. When the object distance is greater than 2 times the focal length, the image distance is between 1 times the focal length and 2 times the focal length, and it becomes an inverted and reduced real image. At this time, the image distance is smaller than the object distance, the image is smaller than the object, and the object image is on the opposite side.

2. When the object distance is equal to 2 times the focal length, the image distance is also 2 times the focal length, forming an inverted and equal size real image. At this time, the object distance is equal to the image distance, the image and the object are equal in size, and the object is on the opposite side.

3. When the object distance is less than 2 times the focal length and greater than 1 times the focal length, the image distance is greater than 2 times the focal length, and it becomes an inverted and magnified real image. At this time, the image distance is greater than the object distance, the image is larger than the object, and the image is located on the opposite side of the object.

4. When the object distance is equal to 1 times the focal length, it will not be imaged, and it will be emitted as parallel light.

5. When the object distance is less than 1 times the focal length, it will become a virtual image that is staring at and magnified. At this time, the image distance is greater than the object distance, the image is larger than the object, and the object image is on the same side.

The imaging rules of convex lenses are:

1. The object distance is greater than twice the focal length, and the inverted real image is reduced.

2. The object distance is equal to twice the focal length, and it becomes an equal large inverted real image.

3. The object distance is between 1 times the focal length and 2 times the focal length, forming a magnified inverted real image.

4. The object distance is less than 1 times the focal length, and the upright virtual image is magnified on the same side.

5. If the object distance is equal to 1 times the focal length, it cannot be imaged.

The memorization formula of the imaging law is as follows: one time the focal length is divided into virtual and real, and two times the focal length is divided into size. The far image of the object becomes smaller, and the near image of the object becomes larger.

Applications of convex lens imaging.

1. Camera.

The lens of a camera is a convex lens, and the distance between the object and the lens (object distance) is greater than 2 times the focal length, forming a zoomed out, inverted real image.

2. Projector.

The lens of the projector is a convex lens, and the distance from the object to the lens (object distance) is greater than 1 times the focal length and less than 2 times the focal length, forming a magnified and inverted real image.

Note: In order to make the image larger for cameras and projectors, the lens should be close to the object, away from the film and screen.

3. A magnifying glass.

Magnifiers are convex lenses; The distance between the object and the lens (object distance) is less than 1 times the focal length, forming a magnified and upright virtual image.

Note: Make the object larger.

4. Eyes. The lens of the eye is equivalent to a convex lens, and the retina is equivalent to a light screen (film). The hyperopic eye cannot see near objects clearly, and the near objects are imaged behind the retina, so they need to wear a convex lens to adjust.

Answer: When the camera imaging, the smaller the object distance, the larger the image distance, the larger the real image, the distance between the lens and the film is the image distance, and the image distance should also change with the change of the object distance; Therefore, when the photographer takes a photo, he finds that the skin of the scene on the ** is too small, and he wants to make the scene on the ** larger, so he should reduce the object distance, let the key make the camera and the scene closer, and increase the object distance, that is, let the lens be farther away from the film, so the lens is stretched forward;

At the same time, the camera is made of a convex lens.

When the object distance is greater than twice the objective focal length, the imaging property is an inverted and reduced real image When the flying insect stops on the lens, the flying insect is located within the focal length of the convex lens, and it becomes a virtual image.

The light screen can't receive it, so there is no image of a flying insect on this **, but because the flying insect blocks part of the light, the light through the convex lens is reduced, so **will become slightly darker

Answer: When the focal length is constant, the sum of the object distance and the image distance will change with the object distance. Solution:

The object is at 2 times the focal length 2f, and the image is at 2 times the focal length 2f, which is a real image of the size of an inverted handstand, and the distance between the image and the object is 4f. When the object is outside the double focal length, the image is between the first focal length and the second focal length, forming an inverted and reduced real image, and the distance between the image and the object is greater than 4F. The object distance varies widely, and the image distance varies small.

The object is between one and two times the focal length, as if it is outside the double focal length, and becomes an inverted magnified real image. The distance between the image and the object is greater than 4F. The range of object distance variation is small, and the range of image distance variation is large.

When a real image is formed, the minimum distance between the image and the object is 4F.

The longer the lens is extended, the longer the focal length. Simply put, focal length is the camera from the center of the lens to the bottom lens.

version of the CCD and other imaging planes weighted distance. Therefore, the longer the lens is extended, the longer the focal length.

The focal length of a lens determines the size of the image of the subject captured by the lens on the imaging plane. Assuming that the same subject is shot at the same distance, the longer the focal length of the lens, the greater the magnification of the image created by the subject on the film or image sensor.

The longer the lens stretches forward, of course, the farther it shines, if you are using a professional SLR machine, the clear effect will be good, and it can also be photographed far away, if you use a card machine, depending on the pixels, the higher the pixels, the clearer, as for the imaging you said, it is related to the light, even if the light at night is not as good as the daytime, there will be noise (the noise is the ** particles appear a little large), the quality of a ** imaging depends on what lens you use, what camera you use, It has a lot to do with the camera's processing chip, and I hope to give you some help.