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Capacitor manufacturers offer capacitor series that are specifically targeted on camera flash applications. For example, Rubycon has the FW series, and NCC has the PH series. These have working voltages of about 300V to 330V and a typical capacitance of 100μF to 150μF, so at first glance these seem to be standard high-voltage electrolytic capacitors. Nevertheless, they are designated for camera flash applications.

What makes these capacitors particularly suitable in terms of ESR, construction, etc. ?

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  • \$\begingroup\$ What Dave said PLUS point a high performance flash at distant darkness while holding it in your hand and fire it. If you bought it new for perhaps $300+ you are liable to wince at the physical kick and thmp it makes. Tough caps! \$\endgroup\$ – Russell McMahon Jan 25 '14 at 14:33
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Camera flash capacitors are constructed to have low resistance, and more importantly, low inductance, so that they can deliver their energy to the flash tube as quickly as possible — which means achieving a fast risetime on the pulse of current. The internal connections are also made more robust in order to avoid localized heating as a result of the high current.

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  • \$\begingroup\$ The flash capacitors I have seen so far have a small diameter and a large length. Is it correct to assume that this shape is not only due to the form factor required but also helps reducing the ESL? \$\endgroup\$ – realtime Jan 25 '14 at 13:16
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    \$\begingroup\$ Possibly, but I suspect it's mostly a matter of the form factor desired by the flash designer. \$\endgroup\$ – Dave Tweed Jan 25 '14 at 13:25
  • \$\begingroup\$ I'll add that I just worked on some 1.2J / 600v flash units, and tried to measure the pulse output into the lamp through a 0.5Ω ladder of twenty 10Ω 1W in parallel. I saw a 400v spike across that 0.5Ω, equating to 800A... 400v*800A = 320kW. It eventually blew the coating right off the resistors. \$\endgroup\$ – rdtsc Jan 31 '18 at 20:39

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