thank you for that informative reply.
so am i really limited to getting a pana oly compliant flash or can I buy a decent flash that I can use on say another body that is not pana if I upgrade? I am hoping for the latter =)
The responses subsequent to this question have incorrect and/or inaccurate information.
Some basic flash synchronization information, reasonably accurate and readable, is available on Wikipedia at
http://en.wikipedia.org/wiki/Flash_synchronization
This includes information about the design of focal plane shutters and how they sync with electronic flash if you follow the appropriate links.
1- Yes, for FP ("high speed") sync, you must use a Panasonic/Olympus dedicated flash unit for Panasonic/Olympus bodies. The same need exists for any other focal plane shutter cameras ... all DSLRs and current interchangable lens digital cameras (Micro-FourThirds, Epson R-D1, Leica M8/9). E.G.: if you want dedicated operation for a Nikon which supports the advanced high speed sync or TTL flash metering features, you must buy a Nikon dedicated flash unit. Only cameras with leaf-type shutters which always fully open on every cycle can be used with a non-dedicated electronic flash unit at any shutter time setting.
2- You can certainly use that same flash unit on other brands of cameras, but you can only use the flash unit's non-dedicated features. For instance, I use a Nikon SB-30 flash unit (which has dedicated features for Nikon bodies) on my Panasonic and Olympus bodies as a trigger flash for simple optical slave setups. However, I cannot use a shutter time shorter than 1/160 second with it on Panasonic or Olympus or TTL metering mode since it is not Panasonic/Olympus dedicated and does not support the specific TTL or FP protocols required for these bodies.
3- You can also buy non-dedicated auto-flash units that will work on any camera ... but you will not get TTL flash metering or FP mode with any of them. You will be limited to whatever your specific camera body's simple X-sync speed is, typically 1/160 to 1/250 second with most of today's cameras.
4- With the appropriate Panasonic/Olympus-dedicated flash unit that supports the FP mode feature (Olympus FL36, FL50, FL36R, FL50R, Panasonic 360 and 500, and some Metz units),
FP sync mode will allow you to use
any shutter time setting without image cut-off due to the shutter curtains. On Olympus and Panasonic units, the FP mode can be used with TTL-Auto metering or Manual mode. I believe it can also be used on certain Metz units in manual mode.
(Jonas:
The Nikon D70 used an interesting hybrid electronic shutter system whereby the flash was triggered at the normal mechanical first curtain fully open point but the sensor's capture could be terminated prior to the second curtain being released to close the shutter. Unfortunately, there remain many problems with such sensor-timed shutter systems as yet which affect image quality, so Nikon has abandoned this particular technology for the present.)
5- FP mode operation essentially works by extending the electronic flash 'burn' time (through very rapid pulsing of the flash tube) to span the time that a focal plane shutter's traveling slit requires to cross the format gate. Since any given flash unit has only so much energy per flash to work with, and the total energy output is an integral of how much power per unit time the bulb is activated, the consequences of extending the unit's burn time is that the total output per flash is lower. The reduction in amount of light output is dependent upon power output setting and the shutter time being used (since those determine the length and number of pulses used to extend the burn time), and is listed in the instruction manuals for each flash unit that supports the feature.
I find FP mode output is typically satisfactory for fill flash at normal single and couple portrait distances in sunlight with the Olympus FL36, but working at larger groups and working at greater distances you might need at least one or two FL50 units to supply enough fill light power for short exposure times.