Quan Huafu lens has a large imaging circle (large field of view), so it needs a larger lens aperture to ensure a larger aperture and better optical quality. Careful observation of the high-end large ternary lens shows that the diameter of the rear lens group is quite large. For the low-end lens, the diameter of the rear lens group is relatively small. Most of the lenses of full-frame cameras are high-end lenses, with large caliber and large quantity, which is naturally quite heavy. The following two pictures compare the lens structure of Canon 70-200/2.8 Xiaobai and 18-55 sets of machine lenses specially used for editing, showing the difference between high-end lenses and low-end dog heads.

Figure 1, Canon 70-200/2.8 lens structure. There are many lenses and large caliber.

Figure 2. The lens structure of Canon 18-55. Few lenses and small caliber.