Am I using the correct settings for external flash?

[gunawan]

Need some expert advice from the CS seniors:

I tried to use a nissin 622 flash on a 70-200 at f4 indoors flourescent lighting at about 2-3 meters (distance to subject) on AV mode.

After pressing the exposure button (ie preflash ), I noticed the shutter speed is a miserably slow 0"3 or something around there, which is almost similar to not using the external flash!?

question: How much increase in shutter speed will I get if I were to use an external flash at full automatic mode?

TV Mode: I then manually switched to 1/180 shutter speed at 70mm FL and shoot the subject with same parameters and the photo turned out perfect, except that my 40D showed an error in the 'aperture setting' (ie. the F4 aperture numeral was flashing, denoting an error)

-Is the above method (TV mode) that I am using the correct way?
-where to read up on how to use external flash?
-do we use tv or av mode when using external flash?

Thanks for sharing. I've always been shooting without flash and now venturing with external flash and found it interesting but confusing.

[calebk]

Read this on how EOS cameras behave with external flashes on semi-auto-exposure modes:

http://photonotes.org/articles/eos-flash/

[gunawan]

Originally Posted by calebk Read this on how EOS cameras behave with external flashes on semi-auto-exposure modes: http://photonotes.org/articles/eos-flash/

Hey Thanks Calebk. That looks comprehensive. will readup.