|
|
| Welcome to World Photography Forum! | |
 | Thank you for finding your way to World Photography Forum, a dedicated community for photographers and enthusiasts. There's a variety of forums, a wonderful gallery, and what's more, we are absolutely FREE. You are very welcome to join, take part in the discussion, and post your pictures!
|
|
|||||||
| General Photography Technique Discussion on General Photography Technique |
 |
|
|
Thread Tools |
|
#11
02-03-07, 23:00
|
||||
|
||||
Clive,
From the description it is all about pre flash as Rob has mentioned. This is discussed a bit in the flash forum. My only contact with Canon was a visiting camera and that only properly worked with a sync lead. I would suggest the only way you will achieve a multiple flash set up is triggering one unit by sync lead and all others by slaves and DO NOT use the pop up. This worked for us using a Canon 300D camera and a mix of various flashguns. Set the camera to manual mode with shutter speed at or below sync speed. Don 
|
|
#12
02-03-07, 23:20
|
|||
|
|||
|
Unfortunately the Canon Master - Slave solution is expensive. That is why I took a soldering iron to the off camera cord to extend the lead.
If your any good at electronics the old style peanut can be modified cheaply. Plenty of circuit diagrams on the web. The peanuts that handle preflash correctly are available http://www.adorama.com/WNPNXLD.html
__________________
Rob ----------------------------------------------------- Solar powered Box Brownie Mk2 Captain Sunshine, to be such a man as he, and walk so pure between the earth and the sea. WPF Gallery Birdforum Gallery http://www.robertstocker.co.uk updated Last edited by robski; 02-03-07 at 23:31.
|
|
#13
03-03-07, 07:42
|
||||
|
||||
|
Thanks all for you input and links and I now understand what is going on.
The camera does indeed fire a pre flash and this is to calculate flash exposure rather than white balance. When using the pop up and a slave triggered remote, when the pre flash fire so does the remote. The camera then calculates the flash exposure from the combined light intensity. As a result is "sees" a higher light intensity, thinks that it will over expose and then throttles back on the output when it fires the pop up during the exposure. By the time this happens, the remote has discharged and is recycling and therefore doesn't fire. The result is LESS light during the exposure as in my 3rd and 7th histograms. The bad news is that, at least in the 20D, the pre flash can't be turned off  The good news is that there is a cheap solution without the need for wires all over the place. Buy a cheap manual non dedicated flash gun which fires from a single centre contact and put it on the hot shoe. Jessops do one with guide No 10 (m @100 ISO) for £10.99 which should do the trick. No need to modfy the flash gun. This will fire at the time of exposure and trigger all the slave units. The light out put can be controlled by the use of ND filers, tissue or a handkerchief in front of the flash tube. I've tried it with one of my bigger auto guns set on manual and it works  Off shopping in a bit
|
|
| Currently Active Users Viewing This Thread: 1 (0 members and 1 guests) | |
|
|
