I posted this question on another site and did not get a useable answer.
I will be shooting a lot of indoor low light situations in the near future. I use a Nikon SB-28 flash mounted on a flash bracket with my Nikon F100. I set the F100 to P = Program mode and depend on the flash's TTL setting and all the electronics to take care of the rest. Sometimes it just won't fire if the light is too low.
The respondent on the other site said that perhaps the flash was not ready (we can rule that out) or that the camera may not fire because it is in "focus priority mode." He goes on to say that the problem may be autofocus because proper focus cannot be achieved in low light situations and then the camera won't fire.
All this is well and good in terms of explaining why the camera may not be firing, but it doesn't do much for explaining my options. If I go to a "manual" setting with the camera and set the aperture to "wide open," what do I do with the shutter speed? How does TTL work under this scenario?