What kind of capacitor do i need, high or low farad rating?
The energy stored in a capacitor in Joules = 0.5 x C x V x V. Joules = W.s As the energy is proportional to voltage squared, that makes voltage very important. The voltage from a disposable flash unit is something like 250V, so you can do your own calculations. The capacitor/s needs to be rated for voltage. Use the same voltage rating or higher than the existing capacitor in the flash unit. The capacitance value is usually in micro-farads. A typical value is 330uF which gives about 10J. A large flash unit may be 60J. The discharge rate depends on what is discharging the capacitor, but with high discharge rates the physical construction of the capacitor and the length of discharge leads connected to it. The leads have resistance and inductance which slow the discharge slightly. Capacitors have an internal resistance called Equivalent Series Resistance (ESR). This should be as low as possible – use multiple capacitors in parallel with short interconnecting wires, or physically large size
