Please give me a simple explanation in this.

Sener wrote:

Last night I was photographing at an event. I had a manual 35mm f/2 lens on my D700.

My normal settings with my camera are; Auto ISO 200-6400 and 1/60 min. shutter speed.

Ambient light was a little off, so I decided to use my flash. I set the flash to -1.0 EV and REAR. When I set it, also SLOW popped up in the info screen.

Normally I don't resort to using flash much, so I am not good with its controls. I just thought that if I set the basic parameters (flash exposure compensation and REAR) it would all be set.

Then things got out of the way. I couldn't control my exposures. When I checked I saw that the camer did not move the ISO beyond 200 (altho I left auto iso ON) and my photos came out underexposed. I manually increased min.ISO to 3200, and then I got good exposures.

From this I understand that with the Flash on and set to REAR, the camera sticks with the min.ISO setting.

Now I made some ISO and flash exposure experiments and I got so much various exposures that are too much to explain. I just could not find the logic.

When I use flash, I always intend to use REAR. So plese save me from digging into this ocean of unknowns, and give me the simplest explanation to use the built-in flash in REAR mode with the least hassle.

Thank you.