NSC published a figure back in the '70's, which was (6000 uF/Ampere)/volt-of-ripple. This means that one needs 6000 uF per amper of output with a tolerable ripple voltage at the input of the regulator, of 1 volt, keeping in mind that there's a dropout voltage for the regulator to be taken into consideration. Tolerable ripple would be above the required minimum input voltage under full load.

Technology hasn't changed the basic premises on which this principle is based. Capacitors are physically smaller, but you still need a certain amount of capacitance to supply a regulator.

I personally have used 8000 uF most of the time, just to be safe. I also use a small high-power resistor between the rectifier and capacitors, to prevent harming the diodes on power-on.

RE