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using flash

Debbiee 14 136 6 United Kingdom
26 Feb 2010 11:54AM
Hi just after some advice again I have a sigma ef-430st flash for my Canon eos 350d and really don't know how to use it, I'm not sure it even works properly as every time I have tried to take images using flash I end up with an awful lot of noise. I don't know about the settings on it which could be the problem i.e TTL etc and just wondered if anyone could give me any advice on using it or point me in the right direction of a tutorial. I have browsed through the ephotozine site but can't seem to find anything on it, thanks for your time Debbie
Overread 12 4.1k 19 England
26 Feb 2010 12:18PM
A flash shouldn't cause noise in a shot - if anything it should be there to help reduce the noise. Have you an example shot with settings as well as the shooting mode you used on the site for us to see which shows this? It's hard to guess at the problem and what it could be.
Even just what shooting mode you use and the settings on your last noisy shot might give a clue as to where the problem is.

One thing I can say though (as its a common thing people don't often understand when new to flash) is that the camera when it meters does not meter for the flash. It still only meters with ambient light which means that the settings it suggests for you will still be similar to those if you did not have the flash. In this mode the flash is effectivly giving you fill flash - it is filling in the shadows in the scene and won't be the dominant light source - this is certainly the case if you shoot in the semi auto modes like aperture and shutter priority and is also how the settings will be metered in full manual mode.
When you fire the shutter the flash preflashes (very fast often you don't see it) and then the meter reads how that light affects the exposure scene and then it fires the main flash blast of light to achive a correct exposure. (note this is why there are two compensation modes - flash and regular - as you essentially have two exposures to control - if the flash gives out a bit too much light (for example) you can tell it to underexpose (using its compensation mode if needed).

This method means that the camera flash is always reactive when in auto rather than proactive in giving the exposure. If you have a darker scene where you are going to use flash more dominatly to be the lighting I find the best mode is full manual for the camera - where you can tell it the aperture, shutter speed and ISO and then let the flash punch out the light as needed. If you have time for test shot this works really well - shoot - review on the camera (histogram is very important to review for this) and adjust settings if needed.
That's the basics - things get much more complicated after that Wink
gaelldew 14 377 United Kingdom
26 Feb 2010 2:33PM
http://photonotes.org/articles/eos-flash/ or your manual, that should have the basics at least
Briwooly 15 454 6 England
26 Feb 2010 2:48PM
Here's a link Flash

Debbiee 14 136 6 United Kingdom
4 Mar 2010 2:04PM
Thanks for your help, I have just uploaded an image taken using flash so you can see what I mean going to have a read through the info you provided and have a practice to see if I can get to grips with it.
Debbiee 14 136 6 United Kingdom
5 Mar 2010 12:31PM
again thanks for all you help and comments to my flash image, i now realise where I was going so wrong i.e I was setting my camera up for the scene as if it where to be taken without flash and had my aperture set very wrong.

I been trying to play around with flash since reading all your helpful comments but still need help!! pictures now are coming out over exposed I set the flash exposure compensation to -2 but still getting very over exposed images, my flash seems to set itself to 50 all the time? whether in a really light place or really dark.

I was just wondering if my flash itself isn't compatible with my camera, I was told when I bought it, that it was compatible but when looking online at a compatibility list I can't see it included. Its a sigma ef-430st and my camera is the Canon EOS 350D does anyone know if they are compatible.

thanks again Debbie

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