Quote Originally Posted by i40west View Post
That's not actually true; the FA can use program mode with both AI and AI-S lenses. The difference between AI and AI-S is that the aperture control lever on AI-S lenses has a linear response (it moves just as far to change by one stop, no matter what stop it actually is).
True. Program mode on the FA will give an accurate exposure with AI lenses, but you have no guarantee that you're getting the shutter speed-aperture combination the camera predicts you will. AI-S (and AF) lenses guarantee that the camera readouts will be correct.