It is often said on the Internet that the magnification of a lens is determined by the focal length and the nearest focal length. Why are the parameters of the two macro lenses almost the same, but th

It is often said on the Internet that the magnification of a lens is determined by the focal length and the nearest focal length. Why are the parameters of the two macro lenses almost the same, but the magnification is 5 times different? It is often heard that the lens can take macro effects of 1: 1 and 1:2, and these ratios refer to the maximum magnification of the lens. The magnification is represented by 1: x, and the magnification = image size (actual size of the subject). Generally, any number on the left or right is classified as 1, which is generally expressed as 1: x or x: 1. The former means that the actual size of the subject is x times that of the image, and the latter means that the size of the image is x times that of the subject. The "image size" mentioned here refers to the size projected on the film or photoreceptor, not the size on the photo. 1:2 means that the actual size of the subject is twice the size of the image, or the size of the image is 1/2 of the actual size of the subject. Many lenses have macro function, but they are not macro lenses. Macro function is an additional function. Strictly speaking, only a lens with a magnification of 1: 1 is a real macro lens.

For example:

If the length of the object is 10 mm and the image on the negative is 10 mm, the lens magnification is1:1;

If the length of the object is 10 mm and the imaging on the negative is 5 mm, the lens magnification is1:2;

If the length of the object is 10 mm and the image is 2 mm on the negative, the lens magnification is 1:5.

According to the magnification, macro photography can be subdivided into close-range photography and ultra-close-range photography. There is no strict definition, but the general definition is:

Close-range photography: the magnification is1:10 ~1:1;

Ultra-close photography:1:1~ 6:1; (More than this magnification, it begins to enter the scope of photomicrography. )

Therefore, the parameters of the two macro mirrors are almost the same, but it is normal that the magnification is 5 times different.