Why does the flash on my camera fire when I half press the shutter release?

guybrush

guybrush

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Rebecca
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So for the past few days I've been reading Strobist Blog and Photonotes to try and figure out how things work, but I haven't really got very far.

I thought the first step before I go out and buy flash kits and what not would be to play around with the inbuilt flash on my 500D, but something very strange keeps happening and I have absolutely no idea why. I'd have thougt this would be a very easy question to find the answer to, but I've not found anything anywhere!

When I half press the shutter release button.. my flash sometimes starts going crazy and continually firing, sometimes it even does it so much that by the time the lens has focussed on the subject the flash needs to wait a few seconds before it can get ready to fire the flash for the actual shot.

Why is it doing this, what is the purpose and how do I make it stop?

I assume that I'm possibly doing something incredibly stupid, so I'd like to know why and then I can stop being so stupid. ;)
 
It does this to assist auto focus in poor light (if I remember correctly). Probably has some fancy name.

Nothing to worry about, it's just doing it's job.
 
You have low light flash focus assist turned on. You can turn it off on the custom functions menu.
 
Was the flash-going-crazy light red or white?

If it was red then it will only happen in low light and I would recommend you leave it on.

If it is a very bright white continuous flashing, you may have accidently pressed the DOF (depth of field) preview button (probably round the corner on the barrel of your lens). When you do this (in low light at least) the flash will strobe so you can try and judge the depth of field...I'd switch this off...and/or stop pressing your DOF preview button.

Hope this helps

Steve
 
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