Lenses that fit the Nikon D850

The mount is the fitting where the lens locks onto the camera, with the contacts the two talk through. Each camera system has its own: Sony E, Canon RF, Nikon Z, Fujifilm X, L-Mount and so on. A lens made for your camera's mount fits straight on. Third-party makers such as Sigma, Tamron and Samyang make the same lens in several mounts, so check you're buying the right version.

Adapters let a lens from another system fit, as long as that lens was made to sit further from the sensor than your camera's own lenses: the adapter fills the gap. That's why mirrorless cameras, with their short mounts, can take most DSLR and film lenses, but DSLRs can't take mirrorless lenses. Electronic adapters pass on autofocus and aperture control; simple ones are just a tube, so you focus and set the aperture on the lens.

Sensor size matters too. A full-frame lens works on an APS-C camera but frames more tightly (multiply the focal length by about 1.5). An APS-C lens on a full-frame camera leaves dark corners unless the camera crops the picture, which most do automatically.

Adapter advice is general: features vary between lenses and camera firmware, so check with the adapter's maker for your exact combination.