The Belair’s auto-exposure range is EV4~EV15.
This means that with ISO 100 film, EV4 is equal to the light situation in a very dim restaurant. Under aperture f/8, exposure time is 4 seconds. Thus, if the light situation is lower than EV4, exposure time will work as EV4. If you are using ISO100 film, you will be able to get correct exposure photo in, for example, a dim restaurant (EV4).
If you are using higher sensitivity film, you will be able to get correct exposure in even dimmer situation (e.g. with ISO 400 film she is able to take photo under EV2, which is like a room with only candles).
Please also refer to the Depth of Field Charts (one chart for each lens!) to get sharp results.