Do you know the difference between HD and SD cameras? The following editor of China Security Network will give you a detailed introduction. The security market is constantly developing and updating quickly. How to occupy a position in the security market also requires practitioners to understand the development status of the security market. As a practitioner in the security industry, do you really understand surveillance cameras? Do you know the difference between HD cameras and SD cameras? Do you know the classification of surveillance camera lenses? Let's literate today.
????The main difference between HD camcorders and SD camcorders. We mainly look at pixels.
????Difference between HD camera and SD camera:
????SD: DVD quality. Generally 720 * 576 or 640 * 480 (4: 3) or 848 * 640 (16: 9), and the value close to it is also counted as SD.
????HD: 1280 * 720I (i stands for interlaced, p stands for progressive. Same below) 16: 9
????Full HD: 1920 * 1080I and 1920 * 1080p, 16: 9. 1440 * 1080 is 4: 3
????Many times, the price-dependent factors of surveillance cameras have a great relationship with the lens. And do you know the lenses of surveillance cameras? Let's take a look at the classification of surveillance camera lenses.
????Long focal length lens
????A telephoto lens is a lens with a field of view of less than 40 ° and a focal length of more than 25mm; for a zoom lens of a camera, it refers to a lens with the focal length adjusted to more than 25 mm. For example, when the focal length is 50 mm, 75 mm, 100 mm, 150 mm, etc. Long focal length lenses are also known as telescope lenses, telephoto lenses, and narrow-angle lenses.
????A wide-angle lens, also known as a short focal length lens, is a lens with a shorter focal length than a standard lens and a field of view greater than 60 °. For a zoom lens on a camera, it is the one with a focal length of less than 25mm. Such as: the focal length is 16mm, 12mm, 10mm and so on.
????A zoom lens is a lens that can continuously change the focal length compared to a fixed-focus lens. It consists of multiple groups of positive and negative lenses. In addition to the fixed lens group, there are also movable lens groups. Through the zoom ring of the lens barrel, the movable lens group is moved to change the distance between the objective lens and continuously change the lens. focal length.
????A wide-angle lens is a lens with a short focal length and a large viewing angle. The purpose of using a wide-angle lens is to achieve a wider field of vision and magnificent artistic effects. For consumer DC, the so-called wide-angle is actually capable of shooting at 28mm focal length. It should be said that 18-35mm is a short-focus lens, also called a wide-angle lens. Below 18mm is called super wide-angle lens or fisheye lens.
????The basic characteristics of a wide-angle lens are that the lens has a wide viewing angle and a wide field of view. The range of the scene viewed from a certain point of view is much larger than that seen by the human eye at the same point of view; the depth of field is long and can show a considerable range of clarity; it can emphasize the perspective effect of the picture and is good at exaggerating the foreground and expressing the scene Proximity, which helps enhance the appeal of the picture.
????Wide viewing angle can cover a wide range of scenes. The so-called wide range of viewing angles means that at the same point of view (the distance from the subject remains the same) with three different focal lengths: wide-angle, standard, and telephoto. Scenery. When the photographer has no retreat, if the scene that is difficult to capture completely with a 50mm standard lens (such as a group photo of a character), then the wide angle lens can be used to easily solve the problem. Furthermore, for example, when shooting a wide field or a tall building in a city, only a part of the scene may be captured with a standard lens, and the wide or tall scene cannot be expressed. And shooting with a wide-angle lens can effectively show the broad momentum of the big scene or the majesty of the towering buildings. Short focal length and long depth of field. When shooting a large scene, photographers generally rely on the characteristics of the wide-angle lens with short focal length and long depth of field. The entire scene from near to far is included in the range of clear expression. In addition, when shooting with a wide-angle lens, if you use a smaller aperture at the same time, the depth of field of the scene will become longer. For example, if the photographer shoots with a 28mm wide-angle lens, the focus is on a subject of about 3 meters, and the aperture is adjusted to F8, then almost from 1 meter to infinity enters the depth of field range. Because of this long depth-of-field feature, wide-angle lenses are often used by photographers as a highly mobile snapshot lens. In some cases, photographers can manipulate the wide-angle lens to focus very quickly without having to focus on the subject. To complete the snapshot.
????Can emphasize the foreground and highlight the distance. This is another important feature of wide-angle lenses. The so-called emphasis on foreground and highlight distance contrast means that the wide-angle lens can emphasize the contrast of near, far, and far more than other lenses. In other words, photos taken with a wide-angle lens have larger things closer and smaller things farther away, which makes people feel that the distance is widened, which produces a strong perspective effect in the depth direction. Especially when shooting with an ultra-wide-angle lens with a very short focal length, the effects of near and far are particularly significant.
????Exaggerated deformation. In general, the subject is exaggerated and deformed is a taboo in the use of wide-angle lenses. In fact, it is not necessary to exaggerate or deform the subject. Experienced photographers often add content to use a wide-angle lens to moderately deform the subject, taking unusually inconspicuous scenes that people have ignored. Of course, using wide-angle lenses to exaggerate and distort the expressions should be based on the needs of the subject matter and less and refined. Regardless of the need of the subject matter, it is not desirable to abuse the exaggerated and distorted expressions of wide-angle lenses in order to pursue grotesque and bizarre effects from the form.
????Wide-angle lenses can be said to have many advantages, and of course you must choose the lens according to your needs. Today ’s surveillance camera knowledge is all about this. Will you?