Basic flash question

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bvphotos
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p.1 #1 · Basic flash question

I don't use the flash much, and I'm finding myself unable to figure out what might end up being elementary knowledge to most of you. I have a 50D and a 5D (classic). The flash is 430EX.

When I use the flash with the 50D in Av mode and the flash in E-TTL mode, regardless of what aperture I select, the shutter speed is 1/250. Which is exactly what I want. Now, I put the flash on my 5D, and the shutter speed automatically selected by the camera in Av mode varies depending on ambient light. It's as though the camera does not recognize that the flash is mounted, even though the flash symbol appears in the viewfinder. Photos taken thus are over-exposed due to the slow shutter speed + flash. To get the shutter speed up, I set the camera to Tv mode and manually set it to 1/250. The aperture then falls to the maximum (say 2.0) and starts flashing, as one would expect for the available ambient light. Having said that, the photos I take in this way are fine. Can someone please explain what's going on? In Av mode, how do I get the camera to automatically select a shutter speed of 1/250?

Nov 18, 2012 at 12:53 AM

anthonygh
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p.1 #2 · Basic flash question

I would theorize that there is a fault in the 5D as the flash appears ok with the 50D....what the camera is doing is responding to the flash going off and reducing the flash output to compensate for the wide aperture...hence the correct exposure. I cannot think (from personal experience) of a normal situation where the flash doesn't determine the shutter speed but it is not doing this. Try cleaning the contacts.

You could probably check this by manually setting shutter speed and aperture and checking whether the flash output responds to these settings and still gives a good exposure...if it does this might be the way to go....from what I remember there is some latitude for manual settings before the flash output cannot compensate for the manual settings.

I use a digital Metz myself so am thinking back to my 430EZ days (film stuff!!)

Nov 18, 2012 at 01:30 AM

devaulrg
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p.1 #3 · Basic flash question

The default is to have the shutter speed as AUTO in Av mode w/ a flash (what the 5D is doing.) Your 50D must have a custom option enabled.

On my 40D, I go to the menu and go to "C. Fn I : Exposure" and the 7th setting in that menu is "Flash sync. speed in Av mode" with the default option being AUTO and the other option being 1/250sec.

Nov 18, 2012 at 01:38 AM

winman3
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p.1 #4 · Basic flash question

Go to your C FN selections in the MENU, then find "Flash synch speed in AV mode" and set the shutter speed you desire. This selection is likely to be under the "Exposure" area of the CFN section.

I use a 5D II now and the above is my setting. The 50D must have the same or very similar set up. I'm not sure about the 5D, haven't used one for a while, but it likely has something similar.

Best of all, learn to use cameras in the manual mode. I can set any aperture and shutter speed (within the flash's range), set my 580EX, 430EX or 430II on EETL and the flash will work perfectly with those settings.

There is much info on using Canon flashes with EOS cameras on several Canon sites,

such as this one.

have fun.....

Nov 18, 2012 at 01:41 AM

anthonygh
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p.1 #5 · Basic flash question

devaulrg wrote:
The default is to have the shutter speed as AUTO in Av mode w/ a flash (what the 5D is doing.) Your 50D must have a custom option enabled.

On my 40D, I go to the menu and go to "C. Fn I : Exposure" and the 7th setting in that menu is "Flash sync. speed in Av mode" with the default option being AUTO and the other option being 1/250sec.

I did wonder if the easy check might not be to put the camera back to the factory default settings.....

Nov 18, 2012 at 01:42 AM

bvphotos
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p.1 #6 · Basic flash question

That's it; it was a custom function that I needed to set. I must have done so on my 50D a long time ago. Thanks for the help, everyone.

Nov 18, 2012 at 02:20 AM

BrianO
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p.1 #7 · Basic flash question

bvphotos wrote: ...Photos taken thus are over-exposed due to the slow shutter speed + flash.

Something still doesn't add up: the flash should have powered down so that it didn't over expose. Was it in ETTL mode?

The only other possibility I can think of was that your ISO setting was so high that even at minimum power there was still too much light from the flash.

Nov 19, 2012 at 06:45 AM

timbop
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p.1 #8 · Basic flash question

bvphotos wrote:
That's it; it was a custom function that I needed to set. I must have done so on my 50D a long time ago. Thanks for the help, everyone.

RTFM

Nov 19, 2012 at 07:15 PM

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