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Archive 2013 · Please HELP
  
 
k clayton
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p.1 #1 · p.1 #1 · Please HELP


Hope someone can please help me out. Did my first indoor shoot with the 5D III and 580EX II speed light. The flash was set to ETTL, My in camera flash settings were Flash Firing :enable, E-TTL II meter:average, Flash sinc speed in AV auto . I was close to my subject using the 24-70 L. I have never had any problems with the 7D and this flash, I always bounce or use a Gary Fong difuser. This time I pointed directly at the subject and got pretty much no light.

Thanks



May 03, 2013 at 11:09 AM
k clayton
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p.1 #2 · p.1 #2 · Please HELP


OK I just changed the in camera C.Fn Flash Metering mode from E-TTL II to external metering mode Manual and that seemed to help...does that make sense?


May 03, 2013 at 12:11 PM
cgardner
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p.1 #3 · p.1 #3 · Please HELP


How strong was the ambient light and what ISO were you using? What doesn't the ambient background beyond the range of the flash look like? Under exposed/ Normal / Overexposed?

Canon ETTL-II flash metering starts with an ambient light reading separate from the one for setting shutter speed in Av mode. Then it fires the pre-flash and compares the two zone maps to see what is underexposed with the ambient and how the pre-flash changed it.

At higher ISO in bright ambient that ambient zone map may be so close to correctly exposed already the metering decides any additional light from the flash will overexpose what in the center of the viewfinder.

That particularly true if the ambient and flash come from the same direction. In backlight (camera facing into the ambient source) the metering will see a difference between the shaded side in the ambient zone map (darker shaded figure in center) and the pre-flash (brightest reflection of foreground subject) and will compute how much flash is needed to raise the shaded center metering zones to match the brighter edge metering zones.

Also a difference in direct vs. bounce mode is that when the head is horizontal the flash metering also uses focus distance information from some USM lenses to compute the flash needed via guide number, factoring in the automatic zoom setting of the flash which is also active when flash is horizontal.. If you add a FongDong to that horizontal flash and it computes the exposure for bare flash the image might wind up underexposed.




May 04, 2013 at 01:22 AM
k clayton
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p.1 #4 · p.1 #4 · Please HELP


Thanks for your response. I was shooting in my family room with a 5x5 backdrop about 4-6 feet from me. The ISO was 400. Ambient light from indirect 7pm sun thru a picture window behind me. I also had some backdrops set up in the basement with no ambient light and the flash did the same thing. The whole thing was underexposed...easily fixed in PS but I had never had this problem before when shooting with the 7D


May 04, 2013 at 11:48 AM
BrianO
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p.1 #5 · p.1 #5 · Please HELP




The flash metering in ETTL mode will depend on the metering mode set (avarage, center-weighted, spot, etc.), so if your subject was light-toned at that spot the camera probably felt that no further light was needed at that high ISO.

The Speedlite's autosensor is reading a more-average reflection from a wider area, and so would give a different reading.



May 04, 2013 at 03:24 PM
RustyBug
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p.1 #6 · p.1 #6 · Please HELP


You mentioned use of the diffuser ... and you mentioned pointing directly at the subject. If I read that correctly, the 90 degree re-orientation of your diffuser has caused you to now have light being radially dispersed from your diffuser directly down toward you flash sensor/lens from a distance of mere inches or so. Your sensor or lens sees that much light, that close and it shuts down the flash output.

Kinda like flash reflecting off aquarium glass, chain link fence, etc yielding a false metering ... only this time it is going directly from flash to sensor.

Remove the diffuser (if pointing toward to subject) or line the bottom (i.e. re-oriented side) of the diffuser to prevent light from going directly from the flash to the sensor/lens.



May 04, 2013 at 04:28 PM
k clayton
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p.1 #7 · p.1 #7 · Please HELP


Rusty I used a defuser with my 7D and I always bounced. I was just trying to explain that the light coming from the flash when I was using it on the 5D III was so poor I needed to point it directly at the subject and it still wasn't enough. Hopefully I will have time to try again this weekend. That has just never happened to me when using other cameras.


May 05, 2013 at 03:13 AM
BrianO
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p.1 #8 · p.1 #8 · Please HELP


k clayton wrote:
...the light coming from the flash when I was using it on the 5D III was so poor I needed to point it directly at the subject and it still wasn't enough. ...That has just never happened to me when using other cameras.


What shutter speed were you using?

Did you have any FEC dialed in?



May 05, 2013 at 03:16 AM
 

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BrianO
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p.1 #9 · p.1 #9 · Please HELP


k clayton wrote:
OK I just changed the in camera C.Fn Flash Metering mode from E-TTL II to external metering mode Manual and that seemed to help...does that make sense?


Manual flash power and external metering (ETTL, too, for that matter) are mutually exclusive. No flash metering is done when manual power levels are set. Maybe I'm not reading this correctly.



May 05, 2013 at 03:23 AM
k clayton
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p.1 #10 · p.1 #10 · Please HELP


Brian I have no idea what I am doing. Was just messing with the in camera controls and set it on manual per something I read on the internet...lol
I can't remember the shutter speed.
And I did not have the FEC dialed in on the flash just in camera. Will have to google how to do that on the flash.
Thank you



May 05, 2013 at 04:51 AM
RustyBug
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p.1 #11 · p.1 #11 · Please HELP


Can you post an unedited version of the picture, so that we can read the raw info @ camera settings contained in the exif data?

You may want to find the "reset" to factory settings button in the menu and try again.



May 05, 2013 at 01:32 PM
k clayton
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p.1 #12 · p.1 #12 · Please HELP


I don't think I can upload here. exif data 2.8, 125, 400iso in the past the flash would have triggered and it would have been very overexposed. Ha maybe its doing what its supposed to do and I just think its not. If you PM me your email I can send it to you
Thanks again



May 05, 2013 at 01:55 PM
BrianO
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p.1 #13 · p.1 #13 · Please HELP


k clayton wrote:
...I did not have the FEC dialed in on the flash just in camera. Will have to google how to do that on the flash.


FEC (flash exposure compensation) is set on the camera, but is seperate from EC ([ambient] exposure compensation).

It may not be the case here, but more than one photographer has accidentally dialed minus FEC into his camera without knowing it and got dark flash photos as a result.

FEC is covered on page 188 of your 5D Mark III User Guide, which I have reproduced here:








May 06, 2013 at 04:51 AM
k clayton
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p.1 #14 · p.1 #14 · Please HELP


Sorry for the late response but the FEC increase helped a lot... Thanks!!!



May 21, 2013 at 08:50 PM
BrianO
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p.1 #15 · p.1 #15 · Please HELP


k clayton wrote:
Sorry for the late response but the FEC increase helped a lot... Thanks!!!


Glad I could help. It doesn't work in every situation, but sometimes it's just what's needed.



May 22, 2013 at 04:07 AM





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