AF or AF-S

brandyk94

I plan to purchase the Nikon 50mm f/1.4 lens, but I have been browsing and noticed that some of the lenses are labeled AF-S instead if just AF. Is there a difference?

houghs

AF-S means that the lens has a built-in motor while an AF lens does not and requires a camera with a built-in motor for autofocus. The D3100 does not have a built-in motor. You can use an AF lens manually focusing with the help of rangefinder. It works fine for apertures of f/3.5 and up, but for lower apertures (fast lenses) it is very tricky to focus correctly. The D3100 has only a pentamirror to get scene into the viewfinder (which means the picture in viewfinder is smaller and darker) and the LCD display is quite rough, so it is not made for comfortable manual focusing. I strongly recommend using AF-S lenses only.