580 + 550ex dual flash [Archive] - Canon Digital Photography Forums

beaconlightboy

12th of August 2006 (Sat), 20:58

i have been using my 580ex as my off shoe flash (on bracket) and my 550ex as a secondary. it works quite well, but just today i noticed, and i don't know why i never did before.. but.

i was testing my camera and took a shot of a light blue subject which i FEC'd + 2/3. The subject came out pretty well exposed with no slave being used. I then kept my +2/3 setting and switched the 580 to master. i then took a picture and wow, over exposed.

shouldn't the FEC work consistently despite the light setup? i had to shoot the shot -2/3 to get it to come out correctly.

sooooo.. what did i miss?

beaconlightboy

14th of August 2006 (Mon), 22:55

wow. no takers.. lol.. great now i need to figure it out myself.

tim

15th of August 2006 (Tue), 01:38

I've subscribed to the thread in case anyone knew the answer. The only reason I can think of is if the single flash didn't have enough power. What happens if you put your ISO on 1600?

Lord_Malone

15th of August 2006 (Tue), 01:55

I'm... dumbfounded.

René Damkot

15th of August 2006 (Tue), 06:32

Maybe you had a flash ratio set up? (A:B as 2:1) That way, the master would be 'overexposing', and the slave 'underexposing' to get the desired ratio. If no slave was present, you'ld get an overexposed image (even more because there was +2/3 FEC). When the 580 is set to 'normal' (not master) there would be no ratio, so flash exposure would be 'normal', thus just a bit overexposed BC of the FEC

PacAce

15th of August 2006 (Tue), 07:32

i have been using my 580ex as my off shoe flash (on bracket) and my 550ex as a secondary. it works quite well, but just today i noticed, and i don't know why i never did before.. but.

i was testing my camera and took a shot of a light blue subject which i FEC'd + 2/3. The subject came out pretty well exposed with no slave being used. I then kept my +2/3 setting and switched the 580 to master. i then took a picture and wow, over exposed.

shouldn't the FEC work consistently despite the light setup? i had to shoot the shot -2/3 to get it to come out correctly.

sooooo.. what did i miss?
Sample images showing each condition you described above could to wonders in helping someone diagnose this "problem". Telling us how you set the flashes in each case would also help a lot. :)