I'm new to the F100 as I'm just getting back into film after long time. My F100 has been displaying a flashing err message after I take a shot. The pictures seem to be turning out OK but who knows if they would be much better with no error message. It's not clear what if anything is not working. I have been through the manual, cleaned contacts on the lens and the body, changed batteries and so on. I called someone who is supposed to be good with Nikon 35 mm film camera repair who told me that it's because I'm using a G mount lens. The manual and all online sources I see say G mount will work fine. I swapped it out for a non-AF D mount and got no error message but that not a fair comparison. One thought I had is that the camera is having trouble with a newer fast prime. I'm using an AF-S Nikkor 50mm 1:4 G. The manual and online forums are saying G mounts should work fine but the highly recommended repair guy is telling me that my problem is the G mount, i.e. I need an aperture ring on my lens. Does anyone have any experience with this? Thanks