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Old Jan 3, 2003, 1:40 PM   #1
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Default External "flashtrigger" and Olympus 730

Hi all!

I'm using an external "flashtrigger" that reacts to the cameras (Olympus C730) built in flash - I don't know what that kind of device is called in english :-(

It works very good when the camera is set to slow sync but any other setting results in underexposed (!) pictures. I'm using the "P" -mode and lightmetering is set to iESP I think.

How comes that the pictures becomes underexposed in the other settings than "slow sync"? I could understand overexposure but not this...

By the way, I guess it doesn't matters but the flash I'm using the external trigger to is a Sunpak 355AF for Canon.
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Old Jan 3, 2003, 5:50 PM   #2
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Quote:
Originally Posted by Micke O
an external "flashtrigger" that reacts to the cameras (Olympus C730) built in flash - I don't know what that kind of device is called in english
I think you mean a “slave cell”

Quote:
Originally Posted by Micke O
It works very good when the camera is set to slow sync but any other setting results in underexposed (!) pictures.
What I guess is :
1) You are using an “ordinary” slave cell
2) Your camera does ”preflash” one or more times ( meaning at least 1 weak burst , then the “right” one )

If the camera does a preflash, it triggers the external flash with this burst , which is not the right time to flash.
When the camera preflash ( to measure whatever parameters, and in red eye reduction, fire another(s) preflash ) , the camera shutter is not opened yet, and the main flash burst is not happened yet. Since the external flash fire with this even, it (the ext.flash) can not fire anymore at the right burst fraction of sec right after ( no time to recharge)

You then got underexposure because of:
a) no useful contribution of the external flash
b) worse : the external flash foul the camera preflash exposure measurement , and end up to reduce even more the internal flash power.

---------

In normal sync mode, the main flash burst is happened at the beginning of the shutter opening , and the preflash did happened already, also the external flash has already fired, so, it remained “dead” during the exposure .

In slow sync mode , the main flash burst is happened at the end of the shutter opening , just before shutting off, so when the camera preflash, the shutter is already open, the preflash trigger the external flash and the external flash fired in the time window of the shutter opening ( of course, still the external flash is not synchronized as slow sync either , it’s too soon for a slow sync then)
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Old Jan 3, 2003, 6:08 PM   #3
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A simple comprehensive way (IMHO) to illustrate in a time scale ….

1) Normal sync:

CamFlash-------Pf-Pf-Pf--------------Fire---------------------------
(Pf=Preflash)

Ext-Flash-------Fire--------------------------------------------------

Shutter-------------------------------OOOOOOOOOOOOOOOO-----
(O=open)


2) Rear sync:

CamFlash-----------------------Pf-Pf-Pf--------------Fire------------
(Pf=Preflash)

Ext-Flash------------------------Fire----------------------------------

Shutter---------------OOOOOOOOOOOOOOOOOOOOOO-----------
(O=open)
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Old Jan 4, 2003, 5:05 AM   #4
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Hello KCan. Thanks for your answer.

I'm sure it's not because of the redeye reduction preflashes - it's easy to avoid the external flash to be fired by those by just aiming the slave cell in the opposite direction - then the preflashes from the camera is not enough to trigger but the "final" flash is by the reflected light.

So, if I aim the slave cell in the opposite direction it works fine with slowsync and redeye reduction (despite the preflashes) but not any other flash settings.

Hmm, I've been studying your illustration and I'll try some experiments.
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Old Jan 5, 2003, 8:06 AM   #5
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Micke O, for your information:

Whatever external flash you are using , this should be a reliable solution for you :
http://www.weinproducts.com/batteryfree.htm
In the article in the bottom of the page , it says:

Quote:
… it even works with system like Olympus which use more than one pre-flash before the main flash …

Also in this page:
http://www.weinproducts.com/safesyncs.htm

Quote:
WEIN DIGITAL SMART SLAVE TECHNOLOGY accurately computes the preflash delays automatically using sophisticated computer algorythms . The slaved strobe fires at extended ranges in perfect synchronization with digital built in flash producing professional results for indoor photographic lighting enhancement.
The WEIN DIGITAL SMART SLAVES are available in all the popular normal flash configurations.
Well , I did not use any Wein product, so I can’t comment , but seems that many people adopt their products. You can email them to have more information.

IMO, that’s the simplest way to operate your flash; still , it’s only a “triggering solution”, your flash must operate in manual or auto-aperture modes.

For TTL mode, you have to get the FL-40 flash, unless there is a specific adapter for your camera ( as for Metz , Sunpak … flashes) .

Regarding your observations, I can’t comment further; but in some camera, the “measurement preflash” is very close to the main flash burst, so it could be difficult, if not impossible, to distinguish the “measurement preflash” from the main flash burst “by eye” .
(what I mean is your external flash could still be triggered by the preflash even if it doesn’t seems so, a pure supposition since I don’t know your cam at all)
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Old Jan 5, 2003, 4:17 PM   #6
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Just seen this:

https://emporium.olympus.com/innards...asp?sku=200661
it’s compatible to your camera:
https://emporium.olympus.com/innards/compatchart.asp


This cord should give you a standard pc connection to use with any flash ( check trigger voltage limitation), a bit pricy for a cord (as other manufacturers ) …
May be you will need a pc to hotshoe adapter as well.

I would change my recommendation … get this cord instead of the wein slaving solution, with the cord, you can turn off the internal flash and save battery / “ready recovery time” of your cam , and it’s technically a better solution .
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