Fill in flash - where am I going wrong?

amumonamission

amumonamission

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Sarah
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I have been struggling to get to grips with the built in flash when I want to use it as a fill in flash. When shooting in the bright sunlight I have been getting a lot of shadows on faces etc from not being able to take the photo with the sun facing the subject all the time. I have tried using my built in flash as a fill in but the the shot is really over exposed. I had a look in the menu settings and saw a setting called flash exp comp, I had a play with that but it made no difference. Where am I going wrong?
 
There is a good description of how eos flash works at the Photonotes website. It is in two parts and is a bit heavy going in places but well worth a read through (twice in my case because I did not understand a lot the first time).

Getting back to your problem with fill flash there is a good section here that explains how the camera will set itself when using flash in each of the main exposure modes (P, Tv, Av & M)

Hope this helps but if not it may be helpful to post an example of the problem so that the more experienced members can have a go at explaining it.

The Full Explanations are here:-

Part I
Part II
 
So you're shooting into the light, sun behind the subject, and wanting to fill-in with flash? Most likely all you need to do is use a higher f/number.

What's probably happening is that because it's a bright day, the ambient light is wanting to push the shutter speed above the max x-sync speed, which is 1/200sec, in order to balance the daylight with the flash. That is the fastest shutter speed you can use with the pop-up flash, because of the way focal plane shutters work (google).

When the flash is on, the camera won't allow you to go faster than this (the flash would only show in a small band across the picture) and if it wasn't so bright you could see the speed flashing a warning in the viewfinder. But it fires anyway, and of course the daylight is way over exposed. There are various ways around this.

You have got to get the shutter speed down to 1/200sec or longer, so use a higher f/number and/or reduce the ISO. With any luck that should fix it. (You could also do the same thing with ND fiilters.)

If you're still having problems, the best solution is a separate flash gun that has High Speed Sync. Most of them do, eg Canon 430EX. This allows you to use flash at any shutter speed. When you switch on the HSS mode, it changes the way the flash operates and instead of one very brief flash, it pulses a stream of flashes extremely rapidly (you can't see it strobing, it just looks like a normal flash to the naked eye) which effectively becomes continuous light while the focal plane shutter completes its cycle.

It works extremely well - I was using it at a garden party yesterday, all on E-TTL auto - perfect. The only drawback is that it uses a lot of power (more than the pop-up can deliver, which is why you need a bigger gun) so range is reduced and recycling is slower. There's so much more you can do with a decent flash and a bit of practise :thumbs:
 
HoppyUK said:
So you're shooting into the light, sun behind the subject, and wanting to fill-in with flash? Most likely all you need to do is use a higher f/number.

What's probably happening is that because it's a bright day, the ambient light is wanting to push the shutter speed above the max x-sync speed, which is 1/200sec, in order to balance the daylight with the flash. That is the fastest shutter speed you can use with the pop-up flash, because of the way focal plane shutters work (google).

When the flash is on, the camera won't allow you to go faster than this (the flash would only show in a small band across the picture) and if it wasn't so bright you could see the speed flashing a warning in the viewfinder. But it fires anyway, and of course the daylight is way over exposed. There are various ways around this.

You have got to get the shutter speed down to 1/200sec or longer, so use a higher f/number and/or reduce the ISO. With any luck that should fix it. (You could also do the same thing with ND fiilters.)

If you're still having problems, the best solution is a separate flash gun that has High Speed Sync. Most of them do, eg Canon 430EX. This allows you to use flash at any shutter speed. When you switch on the HSS mode, it changes the way the flash operates and instead of one very brief flash, it pulses a stream of flashes extremely rapidly (you can't see it strobing, it just looks like a normal flash to the naked eye) which effectively becomes continuous light while the focal plane shutter completes its cycle.

It works extremely well - I was using it at a garden party yesterday, all on E-TTL auto - perfect. The only drawback is that it uses a lot of power (more than the pop-up can deliver, which is why you need a bigger gun) so range is reduced and recycling is slower. There's so much more you can do with a decent flash and a bit of practise :thumbs:
Click to expand...

Interesting post, I have also had a few problems with using fill in flash. Will look into this :thumbs:
 
I`ve applied that thinking to my use of my Nikon sb800 and works a treat in auto FP mode (high syn) and using BL - balanced fill. Great except in brightest conditions at f2.8 when I guess I just don`t have enough power to overcome the sun
 
Excellent, thanks will definately look in to getting a new flash I think as I personally love the shallow DOF I get with using the lower f no settings. On the days were I have had this problem I have usually got the camera in AV mode on the lowest f no and the iso set to 200 so to get the results I want I think separate flash is the way to go.

Thanks, very helpfull advice as usual :thumbs:
 
Cheers guys :) Hope it helps.

On this HSS/FP flash business. Normally it's fine, but because of the way it works the maximum light output is dramatically reduced. That's okay when you're close (typical guess, say up to 10ft or so) but after that even the most powerful gun runs out of puff. The other thing is fighting toe to toe with daylight, which is never a good idea at the best of times.

These are situations where HSS cannot cope and there's a cross-over point where you're better off using normal flash output, even if you have to raise the f/number or reduce ISO to get it. This will bring the shutter speed down to the x-sync level where the camera and flash work much more efficiently. If in this situation you want to use a low f/number for shallow DoF, you will probably be better off using an ND filter. Or move closer!

It seems strange that you would want to reduce the light in order to help out the flash gun, but that's how it sometimes balances out. And that's the reason why strobists love cameras with a naturally high x-sync. There's a new book out covering Canon flash in some detail. It's by NK Guy, who's name was mentioned above - excellent book, comprehensive and clearly written http://www.amazon.co.uk/Mastering-Canon-EOS-Flash-Photography/dp/193395244X
 
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