The importance of having an autofocus motor in either camera or lens
Autofocus is the term for when a camera with his mechanics and electronics adjusts the lens different glass elements so that the desired subject becomes in focus. Today, when bying a camera and/or a lens, the autofocus function is often taken for granted but that has not always been the case and there are still things to watch out for.
On older cameras, there was no autofocus. The photographer had to adjust and focus manually with the focus ring on the lens. When the autofocus technology was introduced in the early 1980s, it quickly became a standard in the cameras and later on also the lenses.
When you, on a newer camera, press the shutter button halfway to focus, it's a motor in either your camera or lens that ensures that the lens elements move and align themselves to put the object in focus. The autofocus motor is either in the lens or the camera, sometimes in both. However, there are both lenses and cameras without an autofocus motor and would they be combined you as a photographer would have no possibility to autofocus.
If we look at these four products; two lenses and two cameras where one version has built-in autofocus motor and the other one has not.
Of the four different combinations above, we can see that as long as there is a built-in autofocus motor in either the lens or the camera autofocus will be supported and work for you as a photographer.
On Lensora, on each camera and lens product page, you will be able to see available and compatible lenses or cameras. We have avoided to display and present combinations of lenses and cameras that together wouldn't have the possibility to autofocus. If you go visit the page of
Nikon AF 50mm f/1,4 D
you will not see that
Nikon D40 is listed as a compatible camera and the other way around, since both of them are missing an autofocus motor.