Questions abount on-camera flash and E-TTL modes on Canon G1X

[tobyjhnsn]

Hey guys,

I've decided I want to get into photography and purchased a canon G1X as my first camera. I'm a bit unsure however of how exactly the on-camera flash works and how E-TTL works in general.
I realise that without CHDK the camera is limited to manual flash in manual exposure mode and that E-TTL works by default on all other exposure modes.
Hopefully somebody may be able to clear up a few uncertainties that I have.

Does E-TTL only affect the flash power? For instance will it increase the aperture if the flash is unable to output enough power. Basically I want to know if by using ETTL its going to mess with the exposure either I have determined or the camera has determined without flash being on.
I notice that generally the shutter is limited to 1/60 second when the flash is open in Av and other exposure mode, however in Tv and M I can lower this even further. Is this due to the sync speed of the flash? If so what are the downfalls of using quicker shutter speeds?
When using manual flash mode in manual exposure mode the flash is adjusted through power, rather than flash exposure compensation. If i expose the photo for the background (leaving the foreground underexposed) and then open the flash the entire photo lowers in exposure. I can see a jump in the light meter on the right. Why is this happening and is it normal for manual flash mode? Its rather annoying if Im trying to expose for a particular part of the photo and rasing the flash changes the reading. Usually in manual exposure mode I set the exposure with the flash down and then open it up and adjust the power for the foreground exposure.


Cheers in advance for any help.

Thanks,
Toby

[swifty]

Hi Toby,
Your flash gripes sounds suspiciously like the ones I had with a G12 and 270EXII.
http://www.ausphotography.net.au/forum/showthread.php?98023-Canon-G12-WP-DC34-underwater-housing-mini-review
The relevant section is just after the first set of pictures.

Since I don't own either items anymore, I can't verify some of the flash behaviour nuances and I'm also extrapolating my experiences with the G12 to your G1x.

1) I'm not 100% sure but I'm pretty sure e-ttl is only measuring flash exposure. I can't check this unfortunately.

2) On the G12, 1/60 was the default shutter flash sync speed for any of the auto/semi auto modes where shutter speed is not a variable, ie. any mode except Tv and M.
The normal max flash sync speed was 1/250th I think. And with high speed sync modes, it can go much higher ~1/4000th I think.
The problem is you cannot change your default sync speed like you can on DSLRs so if you're using Av for example, you're stuck with 1/60th. This may or may not be a problem depending on your shooting habits but for me, it was really annoying. For example you can't 'drag your shutter' in a controlled manner cos even though enabling slow speed sync lets your drop the shutter speed, you can't tell the camera what range to use and the camera often drops it to unuseable ranges like >1 seconds.
This also means if you're already shooting wide open and your ambient's still too dark, your only choice is to up your ISO rather than drop your shutter speed.

3) I don't remember this behaviour. As I recall, you can set ambient exposure manually in M mode and it wasn't affected when you use your flash. But the problem of course is using manual flash is tricky when you're moving around and your subject distance constantly changes. IMO it was unuseable to use manual flash when you're shooting on the move.
Look at your exif, are your exposure settings changing (when set in M mode) as soon as you activate the flash?