430EX question

Started Feb 5, 2013 | Questions thread
apersson850 Senior Member • Posts: 1,209
Re: 430EX question

ihgold2 wrote:

apersson850 wrote:

ihgold2 wrote:

Or maybe, I suppose, I might like to give distance to subject as my input and have the flash tell me the necessary power based on current ISO/aperture.

That's indeed the most common way of doing it, since often you want to be at a certain distance from your subject and you want to use a certain aperture. Only if this brings you outside of the flash' capability, you'll consider changing one of these two parameters.

Thanks. I have a couple follow up questions. I'm not sure if anyone can answer them for me (and maybe they're contained within the two previous replies already and I just need help interpreting

It looks like the 430EX only let's me set the power. Then, when I press the shutter half way, it shows me the distance. Ok, I can back my way into the correct distance by just adjusting the power until my flash-to-subject distance is correct for me. Does that make sense, or am I going about things in an awkward way?

When you are using a flash on the camera, then there are four ways to get the proper illumination of a subject.

  1. Change flash power level.
  2. Change the aperture.
  3. Change the distance to the subject.
  4. Change the camera's ISO setting.

It's up to you which you'd like best. Within certain limits, because if you are already at full flash power, then you have to use one or more of the other three to get correct exposure. As one example. There are countless of possible combinations.

Now if you are using E-TTL, then the camera will adjust the flash power for you, to match the other three conditions. If it can. Once again, outside the power range of the flash this will fail.

Which is why there's a distance scale, since it aids you in telling you which range the E-TTL can work through, if you use E-TTL, or which distance is the correct one, if you set power manually, taking the other settings into account.

Second question: because the 430EX is dependent on being attached to the hotshoe to give me the distance, how can I use the method above when the flash is a Slave off camera? (Does the 430EX II or 580EX II allow for this?)

No, the flash has no way of knowing which distance it can be used at, when it's a slave flash. The calculation it does when it's mounted on the camera does of course require that the flash is able to light up the part of the subject which faces the camera. For all a slave flash knows, if may be aimed so that it doesn't hit the main subject at all, in which case the distance has no meaning whatsoever. The flash may be used to lift a shadow you want brighter, in the background, instead of providing light for the main subject.

But if you do place the slave flash in such a way that it more or less illuminates the surface of the subject that's facing you, then the same distance applies as if the flash was on the camera. The flash just can't know, so it can't compute it for you.

Again, I'm really asking because I just read Understanding Flash... by Bryan Peterson. And he's always writing something like, "I just dialed in my flash-to-subject distance and found the appropriate f/stop or flash power ..." Does that work for some flashes when the flash is off the camera?

If you use E-TTL for flash exposure this is done automatically, even when the flash acts as a slave. Takes that the slave flash system supports E-TTL, though. Canon's own system does, just like some other systems do.

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