What's the difference between fixed focus and zoom lens of SLR camera?

Zoom lens 1. Zoom lens allows photographers to choose different focal lengths, from wide angle to telephoto; 2. The zoom lens allows the photographer to get close to the subject without moving; 3. The zoom lens provides more shooting opportunities because there is no need to change the lens; 4. There is no need to change the lens, which reduces the chance of camera dust. Zoom lenses were very heavy when they first entered the market, and the image quality could not be compared with fixed-focus lenses. With the improvement of design level, the quality of zoom lens has been greatly improved, but for large zoom lens, the loss of quality is still inevitable. Nowadays, professional photographers usually have a number of fixed-focus lenses with large aperture, including: wide-angle lens (20-28mm), 50mm standard lens, portrait lens (80- 105mm) and telephoto lens (180-200mm), which can take close-ups or head and shoulders photos or shoot sports and wildlife themes. So why do they choose so many lenses instead of 1 or 2 zoom lenses to cover these focal lengths? Because some photos cannot be taken with a zoom lens. 1. The fixed-focus lens has a larger aperture. The large aperture can control the depth of field of the photo, and the photographer can guide the audience to pay attention to the most important things in the photo through the depth of field. In portrait photography, it is very important to separate the model from the background. If you notice the advertisements in magazines, you can see many such effects. 2. The additional advantage of large aperture is that it can reduce the sensitivity to reduce the noise of photos. 3. Most fixed-focus lenses have depth-of-field scales, which can easily read out the current depth-of-field range and focal length. This is very useful for shooting that requires strict control of depth of field. 4. The large aperture of the fixed-focus lens makes autofocus faster and more accurate. How many times does your zoom lens have to pull the bellows back and forth to find the focus? Because their maximum aperture is not big enough and the light is not enough. 5. Under the same focal length, the fixed-focus lens is sharper and the recent focusing distance is shorter. 6. The fixed-focus lens only provides one angle of view, which is a good practice opportunity. Photographers can master the advantages and limitations of each focal length through a lot of practice. Zoom lenses can make photographers lazy and unwilling to move themselves to get a better shooting position. The zoom lens will still occupy a place. With the improvement of image quality, one lens can meet most shooting needs. I admit that zoom lens is very important for travel photography, wedding photography and some portrait photography, but I will put my favorite fixed-focus lens in my camera bag. I know I can use the best photos when I need them.