Speedlite blackout image

[jmaphotography]

<p>Shooting an indoor corporate event last night, I was using an on camera 580EXll and placed a 580EX high up on a lightstand in a corner position to help with overall lighting. I was careful not to shoot into the face of the 580EX, but what happened on <strong><em>several ocassions</em></strong>, was that I took 'blacked out' images - LCD was just overexposed to almost black. Both flash guns were plugged into their own Canon external powerpacks. Excuse the following question, but, can anyone throw any light on what happens here? My settings were around ISO 640-1000, Av 4/5.6, Tv around 60-100. Thanks for your imput.<br>

John</p>

 

[jmaphotography]

Just noticed I said 'overexposed' to almost black. The images were totally "underexposed." Is this because the 2 flashes 'corrupted' eachother?

[paul_russell1]

<p>Sounds simply that they didn't flash. Did you do a couple of test shots away from the viewfinder to check?<br>

Was the second 580 set to slave? Was the line of sight obstructed? Was your camera 580 set to flash or master or both?</p>

[jmaphotography]

<p>580EXll was the master, the other was slave. To start off, I had no problems - images looked good and well exposed. I'm just trying to understand the anomaly as to why this 'non flash' ocurrs. </p>

[paul_russell1]

<p>Dud battery, could be either in the slave or master or both?</p>

[mikesc]

<p>My best guess is that the flashes were popping at full power and you were firing shots off quicker than the flash could recycle.</p>

[jmaphotography]

<p>I've been firing both flashes since, and both seem to have more than enough power - so maybe not the issue. Or, could there be some weakness in one or two of the rechargeables?</p>

[cabbiinc]

<p>580 to 580 would be a line of sight trigger. Was it possible that the slave didn't see the master to know when to fire?</p>

[phule]

<p>Unless your test firings since the event were at the same frame rate and same power output, I think Michael Chan's answer is the most likely.</p>

 

[jmaphotography]

<p>Yes, Michael's reasoning does sound very plausible. I'll try a mock up in dim light again and see if it replicates itself.</p>

[picturesque]

<p>If using evaluative ETTL II, the flash metering system will 'shut down' that way when one sees the other go off in the frame. Its a nasty feature of the metering system.</p>

[jmaphotography]

<p>The 1ds3 is set to Average Metering</p>

[PuppyDigs]

<p>Happens to me too when I take pictures faster than the flash can recover power. </p>

[andrew robertson]

<p>It's a well known issue with electronic flashes. Can you imagine how much power would have to be stored to shoot multiple frames per second at full flash power?</p>

<p>Listen to the whine of the flash. It's a big clue.</p>

[phil_shaw1]

<p>This sounds very much like a case of the 580 EXII shutting down due to overheating. In my experience this is exacerbated if you use lithium batteries.</p>

[pbalko]

<p>Your EXIF should provide the time interval between shots, and give you some idea if the master had a chance to recharge prior to the underexposed frames. That might be the first thing to check before trying to replicate the failure.</p>