The lenses in your phone, your car's cameras and your action cam very likely trace back to Yuyao — but not because Yuyao is a lens town. It is a plastics-and-mould city that happens to host Sunny Optical, one of the world's largest makers of camera lenses. It is the opposite kind of place to Danyang.
Ask what Yuyao makes and the honest answer is plastics. The city, in Ningbo prefecture, is one of China's great plastics-and-mould centres, home to the long-running China Plastics City and the China Plastics Expo. Optics is a fast-growing second industry, not the foundation. There is no street of competing lens workshops here the way there is in Danyang. There is, instead, a giant.
That giant is Sunny Optical (舜宇), headquartered in Yuyao and one of the world's largest makers of optical lenses and camera modules. It supplies the camera optics in phones from Apple, Samsung, Huawei, Xiaomi, Oppo and Vivo; it is the global number one in automotive lenses, with roughly a third of that market; and in a single recent month it shipped on the order of 95 million handset lens sets. The action-camera and XR optics, the kind in a sports cam, come from its intelligent-optics arm. One firm, ~34,000 staff, billions in revenue.
Sunny did not grow out of a local lens trade; it built one from the inside. Rather than draw on a pre-existing cluster, it integrated its own supply chain vertically, and the smaller optics firms in the area exist largely to feed it. That is the signature of an anchor-company town: the company is bigger than the place, and the place would lose the industry if the company left. You cannot shop Yuyao for a camera lens; you deal with the giant, or with the suppliers in its orbit.
Set Yuyao beside Danyang and you have the whole typology of this atlas in one product family. Danyang is a cluster town: the eyeglass-lens industry is hundreds of interchangeable competitors, and you source by walking the market. Yuyao is an anchor town: the camera-lens industry is, essentially, one company, and you source by meeting its terms. Same English word, lens; opposite shape on the map.
For sourcing, the distinction is practical. Need spectacle lenses, or anything that behaves like a commodity with many makers? Go to Danyang's market and let them compete. Need a camera or action-cam lens module? You are really choosing between Sunny and a handful of module houses near Shenzhen that already feed the action-cam brands. Knowing which kind of "lens city" you are dealing with tells you how to buy before you ever board the plane.