First of all, iPhone Pro and iPhone Pro Max have 3 rear cameras, while regular iPhone and iPhone Plus have only 2 rear cameras. Regular iPhone and iPhone Plus don't have a telephoto camera.
If you compare the main camera of iPhone Pro and regular iPhone, you will find the following differences: | iPhone 15 | iPhone 15 Pro |
Maximum resolution | 48 MP | 48 MP |
Sensor pixels | 1 um at 48 MP, 2 um at 12 MP | 1.22 um at 48 MP, 2.44 um at 12 MP |
Lens focal length | 26 mm | 24 mm / 28 mm / 35 mm |
Aperture | 1.6 | 1.78 |
iPhone 15 Pro camera has a larger sensor pitch and allows to change the focal length. There are some other advantages of iPhone 15 Pro Camera, which make it better.
So iPhone Pro have a better main camera than regular iPhone. The "Pro" camera is more capable and versatile.