The difference between HD cameras and SD cameras

Do you know the difference between HD cameras and SD cameras? The following is a brief introduction to the Pacific Security Network. The security market is constantly evolving, and the replacement is fast. How to occupy the position in the security market requires practitioners to understand the development status of the security market. As a practitioner in the security industry, do you really know about surveillance cameras? Do you know the difference between HD cameras and standard-definition cameras? Do you know the classification of surveillance camera lenses? Today, we will sweep literacy for everyone.

The main difference between HD cameras and SD cameras. We mainly look at pixels.

The difference between HD cameras and SD cameras:

SD: DVD quality. Generally 720 * 576 or 640 * 480 (4: 3) or 848 * 640 (16: 9), close to its value is also standard definition.

HD: 1280*720I (i stands for interlaced, p stands for progressive. Same as below) 16:9

Full HD: 1920*1080I and 1920*1080p, 16:9. 1440*1080 is 4:3

Surveillance cameras often have a large relationship between the price and the lens. And do you know the lens of the surveillance camera? Let's take a look at the classification of the surveillance camera lens.

Long focal length lens

A long focal length lens refers to a lens with an angle of view of less than 40° and a focal length of more than 25 mm; for a zoom lens of a camera, a lens with a focal length adjusted to be greater than 25 mm. Such as: focal length values ​​of 50 mm, 75 mm, 100 mm, 150 mm, etc. Long focal length lenses are also known as telescope heads, telephoto lenses, narrow-angle lenses, and the like.

Wide-angle lens

A wide-angle lens, also known as a short focal length lens, is a lens that has a shorter focal length than a standard lens and an angle of view greater than 60°. For the zoom lens on the camera, the lens with a focal length of less than 25 mm. Such as: focal length is 16mm, 12mm, 10mm and so on.

A zoom lens is a lens that continuously converts a focal length with respect to a fixed focus lens. It consists of multiple sets of positive and negative lenses. In addition to the fixed mirror set, there are still movable mirror groups. Through the zoom ring of the lens barrel, moving the movable lens group and changing the distance between the objective lens, the lens can be continuously changed. focal length.

Wide angle concept:

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 view and magnificent artistic effects. For consumer DCs, the so-called wide-angle is actually equipped with 28mm focal length shooting capability. It should be said that 18-35mm is a short-focus lens, also called a wide-angle lens. Below 18mm is called a super wide-angle lens or a fisheye lens.

The advantages of wide angle:

The basic feature of the wide-angle lens is that the lens has a large viewing angle and a wide field of view. The range of scenes observed from a certain point of view is much larger than that seen by the human eye at the same viewpoint; the depth of field is long, and it can show a fairly clear range; it can emphasize the perspective of the picture, and is good at exaggerating the foreground and the scene. The sense of distance, this helps to enhance the appeal of the picture.

The range of viewing angles is large and can cover a wide range of scenes. The so-called range of view is large, that is, at the same viewpoint (the distance from the subject remains unchanged), the photographic lens with three different focal lengths of wide angle, standard and telephoto is used for framing, and the result is that the former shoots more than the latter in the up, down, left and right directions. Scenery. When the photographer does not have a retreat, if it is difficult to fully capture the scene with a 50mm standard lens (such as a group of people taking pictures, etc.), the wide-angle lens can be used to solve the problem easily. In addition, if you shoot a vast field or a tall building in the city, you may only be able to capture a part of the scene with a standard lens, and you cannot express the width or height of the scene. Shooting with a wide-angle lens can effectively show the grandeur of a big scene or the majesty of a towering building. The focal length is short and the depth of field is long. In the shooting of large scenes, photographers generally rely on the wide-angle lens with a short focal length, and the characteristics of the scene are long and deep, and the entire scene from near to far is included in the clear performance range. In addition, when shooting with a wide-angle lens, the depth of field of the subject becomes longer if a smaller aperture is used at the same time. For example, the photographer shoots with a 28mm wide-angle lens, and the focus is on the subject about 3 meters, and the aperture is adjusted to F8, then almost from 1 meter to infinity has entered the depth of field. Because of this long depth of field, wide-angle lenses are often used by photographers as a highly mobile snapshot lens. In some cases, the photographer can manipulate the wide-angle lens with almost no focus on the subject. Complete the capture.

Can emphasize the prospects and highlight the near and far contrast. This is another important feature of wide-angle lenses. The so-called emphasis on the foreground and the emphasis on the near and far contrasts means that the wide-angle lens can emphasize the contrast of near and far smaller than other lenses. That is to say, the photos taken with the wide-angle lens are larger in the near and smaller in the far, so that the distance is opened and the perspective is deep in the depth direction. Especially with ultra-wide-angle lenses with very short focal lengths, the effect of near-large and small is particularly significant.

Can be 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 unacceptable that the subject is properly exaggerated and deformed. Experienced photographers often add content to use the wide-angle lens to make a moderate deformation of the subject, making some very inconspicuous, unrecognizable scenes unusual. Of course, the use of wide-angle lens for exaggeration and deformation of the expression, one must be based on the needs of the subject, the second is less and fine. Regardless of whether the subject matter is needed or not, it is not enough to abuse the exaggerated and distorted expression of the wide-angle lens to blindly pursue the grotesque and bizarre effect.

Wide-angle lens can be said that there are many advantages, and of course you should choose the lens according to your needs. Today's surveillance camera knowledge will tell you this, will you?