Many mains powered studio flashes have a flash duration in excess of 1/1000 of a second. In fact few achieve a duration shorter than 1/3000th. The older the model the longer that tends to be.
Also, flash of European design tends to have longer duration than that made in the USA. E.g Bowens 2000 (about 30 years old ) has a duration of 1/300th and that measurement is not the whole of the light output just t0.5. The actual length of burn is nearer 1/125th. My current equipment (Bowens 3000G) has a duration of 1/429th on full power, again to t0.5. If I use a shutter speed faster than 1/90th the shutter is not open throughout the flash burst. At 1/250th almost a stop of light is lost and the colour shifts slightly cool. This is a characteristic exploited by Bron in their latest packs, which have adjustable duration/colour temperature. And it's not just studio flash. The Metz 60 has a duration of 1/200th and the 45 1/300th! on full power. All this without taking in to account the few milliseconds delay after triggering by whatever means (IR, Radio, Sync lead, etc.) In the studio, where the ambient light level is usually controllable, the shutter speed is irrelevant, as the only image forming light is the flash. So when Canon suggest a slower sync speed than the camera is capable of with Speedlites, it is with good reason. Regards, Craig Z ----- Original Message ----- From: "Karen Nakamura" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Wednesday, February 20, 2002 9:29 PM Subject: Re: EOS Eos 1d flash sync speed > > > > What they're really trying to say is that large studio flash units tend > >to produce longer-duration pulses of light than small portable units. So > >it may be necessary to limit your shutter speed to 1/125 to avoid flash > >sync problems. > > > > No, that's not the real genesis of the problem. Studio flashes range from > 1/10000 to 1/1000 of a second in flash duration. > > It's not how *long* the flash duration is, but *when* it is. The X sync > standard is a bit loose in that regard. With the E-TTL protocol, the camera > can tell the EX flash exactly when to flash, even when wireless (I imagine > it sends out a notification to tell the unit to flash exactly 0.01 seconds > from now). > > With the X-sync, it's a simple relay and the flash might take up to a > couple of milliseconds to make up its mind. This is exacerbated when you > have radio transmitters involved. The reaction time of the entire system > has to be fast enough for the camera. > > That's why Canon has a rather conservative 1/125 X-sync for non-EX flashes. > It's not that other flashes might not react fast enough, it's just they > can't guarantee it. > > In any case, give it a try, you might find that your system is fast enough > for 1/250 or even 1/500. > > Karen * **** ******* *********************************************************** * For list instructions, including unsubscribe, see: * http://www.a1.nl/phomepag/markerink/eos_list.htm ***********************************************************
