Camera knowledge

1, wide angle: that is, the camera lens has a wide viewing angle, that is, it can accommodate more scene ranges within a limited distance. The parameter to measure the wide angle of a camera is the minimum focal length. Generally, the one less than 28 mm is called wide angle, and the smaller the wide angle, the wider it is, which is suitable for shooting large scenes of scenery and architecture as high as possible, but it will also be accompanied by the deformation of the picture. The closer you get, the more deformed you are, which is not suitable for close-up of people. At present, the lowest DC wide-angle can reach 24 mm, and the wide-angle lens is mainly suitable for shooting larger scenes, such as architecture, scenery and other themes. When taking scenery, it can be used to take wider pictures, and when taking group photos, it can accommodate more people and so on. At the same time, wide-angle lens can produce the effect of big prospect and small prospect. The distortion of the picture produced by wide-angle lens exaggerates the foreground object, highlights the foreground object more, and gives people a strong visual impact. Wide-angle lens has a wide viewing angle and can cover a wide range of scenery. The so-called wide viewing angle range means that at the same viewing point (the distance from the subject is constant), the scene is viewed with wide-angle, standard and telephoto lenses with three different focal lengths. As a result, the former shoots more up, down, left and right scenes than the latter. When the photographer has no retreat, it is difficult to take a complete picture (such as taking a group photo) with a standard lens of 50 mm ), using a wide-angle lens can easily solve the problem. Furthermore, for example, shooting a vast Yuan Ye or a tall building in a city, perhaps only a part of the scenery can be photographed with a standard lens, which cannot show the breadth or height of the scenery. Shooting with a wide-angle lens can effectively show the open momentum of large scenes or majestic buildings. Short focal length and long depth of field. Photographers usually rely on the short focal length and long depth of field of wide-angle lenses to bring the whole scene from near to far into a clear range of expression when shooting a wide scene. In addition, when shooting with a wide-angle lens, if a smaller aperture is used at the same time, the depth of field of the scene will become longer. For example, if a photographer shoots with a 28 mm wide-angle lens, the focus is on a subject about 3 meters, and the aperture is adjusted to F8, then from 1 meter to infinity, it almost enters the depth of field. It is precisely because of this long depth of field that wide-angle lenses are often used by photographers as fast-moving lenses with strong maneuverability. On some occasions, the photographer can quickly capture the picture by manipulating the wide-angle lens without focusing on the subject.

2. Wide-angle lens: Before introducing the wide-angle camera, first understand the focal length of the camera. In fact, when people talk about the focal length of a digital camera, they are not talking about the actual focal length of the digital camera, but about the equivalent focal length, that is, the focal length relative to the traditional 135 camera. From the principle of photography, the smaller the focal length, the wider the field of vision, and the wider the range of scenery that the photo can accommodate; The larger the focal length, the narrower the field of view, which means that you can shoot distant objects. In traditional cameras, wide-angle lenses over 28mm are very popular. However, due to the particularity of small photosensitive devices in ordinary digital cameras, the physical focal length of the lens needs to be very short to achieve a wide angle, which leads to high requirements for aberration correction and anti-glare coating. With people paying more and more attention to wide-angle shooting, now around 3000 yuan, cheap wide-angle digital cameras are becoming more and more popular. For most popular digital cameras on the market, the wide-angle focal length is generally between 35 and 38 mm.

3. Application of wide angle in digital camera: It can emphasize the foreground and highlight the contrast between far and near. This is another important performance of wide-angle lens. The so-called emphasis on foreground and far-near contrast means that wide-angle lens can emphasize far-near contrast more than other lenses. In other words, the photos taken with wide-angle lens are closer and farther, which makes people feel that the distance has been widened and has a strong perspective effect in the depth direction. Especially when shooting with a super wide-angle lens with short focal length, the effect of being near big and far small is particularly remarkable. Can be exaggerated and deformed. Generally speaking, it is taboo to use a wide-angle lens when the subject is exaggerated and deformed. In fact, it is not necessarily undesirable for the subject to exaggerate and deform appropriately. Experienced photographers often add content, use wide-angle lenses to moderately deform the subject, and take some very inconspicuous scenes that people turn a blind eye to. Of course, using a wide-angle lens to express exaggeration and distortion should be based on the needs of the subject matter, and the second should be few and precise. No matter whether the theme is necessary or not, it is not worthwhile to abuse the exaggerated deformation of wide-angle lens and blindly pursue the bizarre effect in form.

4. Advantages of wide-angle digital camera: First, it can increase the sense of spatial depth of photographic images. Second, the depth of field is long, which can ensure that the scene before and after the subject can be clearly reproduced on the screen. Therefore, the vast majority of modern pocket automatic cameras (commonly known as fool cameras) use ordinary wide-angle lenses of 38-35 mm Thirdly, the lens covers a large area and shoots a wide range of scenery. 4. The scene shot at the same shooting distance is smaller in the picture than the scene shot with the standard lens. Fifth, perspective distortion and image distortion are easy to appear in the picture. The shorter the focal length of the lens and the closer the shooting distance, the more obvious this defect is.

5. Equivalent focal length: refers to the focal length of the lens when the size of the camera negative was 135 in the past. For example, in the 135 camera, the lens with an actual focal length of 28mm is shot at a normal wide angle. At present, some digital cameras are card machines, and their ccd size (equivalent to the negative) is much smaller than the original 135 negative, that is, the ccd of SLR, such as Canon 10D, is also smaller than the negative of 135, that is to say, the negative of 135 is Canon1. For example, the 50mm lens used on the DSLR of APS-c mentioned above, the equivalent focal length of its 135 camera is 75 mm ... Because 75mm=50mm* 1.5, here 1.5 is the so-called "focal length conversion factor". 135 film cameras all use the 35mm film shown in the above figure, while the CCD/CMOS size of digital cameras is often relatively small. For the same lens, the viewing angle of digital camera is smaller than that of 135 camera, and the decrease of viewing angle can be equivalent to the increase of focal length (the viewing angle is inversely proportional to the focal length). There is such a simple method to calculate the zoom factor of a digital camera. For example, the CCD size of Nikon D80 is about 24 mm x16 mm. We divide the imaging plane width of 36mm film by the CCD width of Nikon D40, and the zoom factor is 1.5. When we add 18mm fisheye lens to Nikon D40, the equivalent focal length of this fisheye lens is 18* 1.5=27mm.

I wonder if the answer is satisfactory.