How do I make a Canon flash do what I want?

lodious

lodious

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I'm pretty new to using an external flash, so forgive me if this is obvious....

I'm using a 550D w/EX420 flash and 50mm f1.8 to do indoor shots of our toddler. I'm boucing the flash to soften the light.

I've tried using the Portrait mode, but if always selects F4.0 as the aperture, which seems a shame, as I'd like to use the lens wide open. I've tried using Av mode, but it selects a shutter speed of 30th of a sec (i.e. I think it's not factoring the flash for the exposure, the flash is used as fill only), which is too slow.

What I really want it is to select aperture at 1.8, shutter speed at (say) 1/125 and have the flash provide the correct amount of light for the shot. Can this be done?

I've been using manual mode to do this, ant i'd not turing out too bad, but I think it would be better to have the security of the camera doing to work for the correct exposure?
 
I have very limited knowledge of this, having only recently started playing with flash myself, but I think what you're doing is correct, and the only way to do what you want.
 
I have the same problem with av. I just set to manual mode when using flash.
 
Try and wrench yourself off the scene modes. Of you want f1.8 1/25 set the camera and do it. You will only improve by practice
 
Av will, as I understand it, always set the shutter to expose for the ambient light and then the flash will be used as fill-in only. Same with Tv where the aperture will be set for the ambient light. I believe the flash will only expose to illuminate the scene in P, where you get no control over the aperture or shutter speed, as you have found, or M, where you do.

I am sure that someone will correct this if I am wrong, and if I am, I would like to know too!
 
Stick it in manual, aperture at f:1.8 shutter speed at 1/125 or whatever you want and set the flash to TTL, that way the camera will decide how much flash it thinks it needs, even bouncing the flash it should be close. If it's a little dark you can dial in a bit of positive flash compensation to increase the exposure.
 
So even in Manual, it adjusts the flash intensity to correctly expose to picture?
 
lodious said:
So even in Manual, it adjusts the flash intensity to correctly expose to picture?
Click to expand...

If you set it that way then it will.

To get the camera settings you want, put it in manual and make the settings. Set the flash to Canon's equivalent of iTTL (I'm a Nikonite), intelligent Through The Lens, and away you go. Take some practice shots and if necessary you can dial in some flash compensation if they're too bright or too dark.

iTTL mode uses the camera's metering to measure the amount of flash needed. It fires a few low power pre flashes, measures the incoming light, calculates how powerful the main flash needs to be for correct exposure and fires it at that power. It should result in a correctly exposed shot using your desired camera settings.

So, camera in Manual, flash in iTTL.
 
Last edited:
Andy

Thanks a million for that. Been reading this thread as I had exactly the same thoughts as OP, and that website is exactly what I've been looking for.

:)
 
The link that Andy posted is worth getting your head around.

It's worth knowing that the camera settings adjust the logic of how the flash metering is applied and so, can vary the exposure differently - can be useful if you can remember all the settings. However (as already mentioned) it's actually easier to set the camera to manual and let the flash 'do it's thing', :) the flash will be in ETTL mode (by default) and will look after exposure (mostly) and you can adjust your manual camera settings to suit.

If in doubt - Chimp.
 
Just to "Canonise" Stratman's advice above.....

Set the body in manual and the flash in ETTL, dial in the aperture and shutter speed as required. Centre your subject in the frame, focus and then press the <FEL> button (probably the * button on your 550D). Take a shot and review the results. If you want boost the effect of the flash a little then repeat the proceure but after pressing the <FEL/*> button, dial in a little extra exposure from the flash (you should see the additional exposure bar in the viewfinder). It'll become a little more intuitive when you have practiced for a while.

Bob
 
Be aware that if you use this method using direct flash, and set the aperture and shutter speed settings in manual, that only the subjest will be exposed correctly. The background will be dark if it is any appreciable distance behind the subject. Bouncing the flash as you say you do will help lessen this.
 
As said you need to read up on how flash works in each of the modes on Canon cameras. Forget about all of the auto modes, you want to be using either P or M for this sort of thing.

Av will always try to expose the background correctly, even if it means using a long shutter speed. P will try to expose the background correctly providing there's enough light - it will not use a shutter speed slower than 1/60 so you could end up with a black background.

Regardless, in any mode the flash will always try to expose the foreground (subject) correctly.

Do not mistake M for manual flash...the flash exposure is always handled by ETTL unless you switch the FLASH to manual mode, which you probably do not want to do.

If you don't care about the background then just use P - it will do its best to give you some background but it will not risk camera shake.
 
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