E-TTL query

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michaelho

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So E-TTL works but firing off a pre flash and then after metering it's strength it sets the flash power to appropriate power. Is this right?

I have just got my 580EX and have set it to ETTL, however I haven't noticed a pre flash. The flash is set to ETTL with auto zoom mode, the 400D is set on Manual mode.

Is this right?
 
Have a look through this
 
Worth adding that the pre-flash and final flash happen within milliseconds of each other and you see it as a single burst. Some people to react to the pre-flash and blink just as the main one fires which can be a right royal pain :(
 
That is so right... the wedding I did had lots of half closed eyes. Bloody nuisance. You can flash it first by hand.. then do the real one.
 
Thanks for that link Janice, it gave me a better insight.

I'm slightly confused in using the flash now. The exposure meter on my camera seems to not be fully representative unless I point the flash towards the subject.
e.g. I point the flash to the ceiling, I set my aperture and shutter timer, the Av meter says its nearly 2 stops under exposed but when I take the photo it's fine.

Am I supposed to ignore the exposure meter or am I doing something obviously wrong here?
 
The meter only shows the ambient light reading, not the flash. The flash metering is only done when you take the shot.
 
So do I just set the settings I desire and the flash automatically will compensate for the light needed?
 
Yup, tho you might want to add some exp. comp. for the flash depending on the situation, eg. fill flash outside maybe -1 FEC, bounced off the ceiling indoors maybe +2/3 FEC.
 
thanks for that pxl8.
What's the difference between fill flash and bouncing off ceilings?
 
Fill flash is when you just add a bit of light into the shadow areas, say on a sunny day or if your subject is backlit. It helps to balance out the extremes of highlight and shadow areas and control contrast.

Bouncing off the ceiling is normally when the flash is the main source of light and you bounce it to soften the light.

There's a good read about using flash here:

http://planetneil.com/tangents/flash-photography-techniques/
 
many thanks for the link, really need to find out more about how to use the flash.

So the difference between fill flash and bounce flash is just the situation you use flash in? There's no specific settings (apart from FEC) for each of them.
 
You can't really say there's a difference between bounce and fill because you can both at the same time.

When you use fill flash you will expose for the existing light as you normally would and the flash will add a bit in the shadow areas. If the scene is too dark then the flash stops being the fill light and becomes the main light instead but all of this is automatic as the amount of light out of the flash is decided by the ETTL calculations in camera. The only time this doesn't happen is if you set the flash to manual mode, then you have to do the maths instead.

Bounce isn't a mode or setting, you physically rotate the flash head so it is pointing at the ceiling or wall and the light is bounced off that before hitting the subject giving a much softer result.
 
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