What is the difference between a 90mm fixed-focus macro lens and a 40mm fixed-focus macro lens?

Macro lenses of 40mm, 90mm and 180mm can all reach the magnification of 1: 1, and the difference is only the "working distance". The "closest focal length" can be found in the lens specification, and the distance from CMOS to the closest focal point of the lens includes the "lens length". And "working distance" is "closest focal length-lens length". Working distance is an important index of macro lens, which determines the shooting convenience of macro lens.

In order to get a larger magnification, the macro head must be close to the object, and the maximum magnification is 1: 1. At the same magnification 1: 1, the working distance of a 40mm lens is usually about 2 cm, 90mm (100 mm) is usually about 20 cm, and 180mm is longer. Therefore, it is difficult to shoot insects with a 40mm macro head because the distance is very close. 180mm macro is good at long-distance shooting, but it has the same depth of field as other telephoto lenses. So most people choose a compromise of 90mm (hundreds of micro). 40mm depth of field is suitable for macro shooting with environment, which is often called "super depth of field".

When it comes to working distance, we have to mention another lens index "internal focus". The so-called internal focusing means that the length of the mirror remains the same when focusing. Therefore, the working distance of the focusing lens is longer than that of the non-focusing lens. One reason why the original Budweiser was expensive was internal focusing.