55 200mm is equivalent to several times the optical focal length of a traditional camera.

1, you asked how many times to zoom, and it is like this:

200/55≈3.6 That's 3.6 times.

70 to 300 is 300/70≈4.3 times.

Always like this.

2. Because of photo books or other situations, we always say that 28 has a wide angle (its viewing angle is 74 degrees), but this 28 is aimed at 35MM cameras. The size of the negative or CCD is different, and the viewing angle of 74 degrees is not necessarily the focal length of 28. In order to facilitate communication and understanding, there is an established method: all of them are converted into the equivalent of a 35MM camera, which makes it easier to communicate and understand.

As for what 55-200 is equivalent to, it depends on what kind of machine you are. Its manual will tell you a coefficient.

For example, if the coefficient of Canon 450D is 1.6, then 55-200 times 1.6 is 88-320, which is equivalent to 88-320MM zoom lens of 35MM camera. On Quan Huafu digital camera, it is still 55-200, because the coefficient of full-frame camera is 1.

By the way, where did Canon's 450D coefficient come from? Well, the size of Canon's 450D CCD is 22.2× 14.8mm, and the size of 35MM film is 36×24MM, using 36÷22.2≈ 1.6, and the coefficient is thus obtained.

After reading your supplement, I don't know what 88-320 means. I can only say this simply:

A lens of 55-200MM is the shortest focal length to express the truth of this lens, and the longest focal length is 200MM, which can vary from 55 to 200. Assuming that the lens is fitted with Canon 450D, due to the image size, its viewing angle effect is equivalent to the zoom lens of 35MM camera with 88-320MM.

As for where this focal length is used in photography, you should read the technical books of photography.

The CCD of Nikon D60 is 23.6 x 15.8 mm, and the coefficient is 1.5.

On page 180 of Nikon D60 manual, there is an effective angle: I have told you that the coefficient is 1.5.