Canon Speedlite Questions

[GTP 290]

*facepalm

Step 1: Cover the flash with your hand.
Step 2: Press the shutter button half way.
Step 3: Allow the camera to focus.
Now this bit is tricky so read carefully.
Step 4: Remove hand from flash unit while still holding the shutter button half way down.
Step 5: Once you hand has been removed press the shutter button the rest of the way down.

[Scotty72]

And... the pre flashes only happen at stage 5

So, steps 1-4 are completely, utterly, totally, absolutely (clear) irrelevant.

[Scotty72]

If you are still not convinced, try this.

Put the camera in manual mode (or TV)

set the shutter speed for 2 secs (so there is a huge delay that is obvious)

set your flash to 2nd (rear) curtain sync (so the main flash is at the end of the exposure and pre-flash is just prior to it)

make sure your 430ex is ready

do the half press and focus the camera (where you put your other hand is your business )

keeping your shutter button half pressed, pause to make sure that operation has finished.

then, when you're ready fully press the shutter button.

You will then notice (a distinct but, small and short) pre-flash.

Count two seconds (or whatever the shutter speed you choose is) then you will notice the main flash pulse.

Normally, if you have a shutter speed of 1/10 th or faster, the gap between pre-flash and main flash is too short for anyone to notice.

Scotty

[Scotty72]

If you need yet more convincing

Use the FEL lock to set the pre-flash off (and lock that reading in) prior to the exposure, then, turn the room lights off. You will find that because your flash setting is locked, that it wont react to the lights going off - so the flash will be a fraction of what's required.

[Scotty72]

If you remain sceptical, I can think of one more test.

You might be thinking that pre-flash in the 2 sec, rear curtain test was part of the exposure.

Try this. (you'll need a tripod)

Set the shutter speed to 20 secs (long enough to do what I am suggesting) - make sure rear curtain is still on

Pre focus. pause etc just like the other test.

Only this time, once the pre-flash has gone off, turn off the flash head - remove it, smash it, burn it and place a curse on it before launching it into deep space - so it will not go off and ruin this test.

After 20 seconds (by the way, turning the flash off is sufficient - you don;t have to smash it to atoms), the exposure will end but, obviously, the main flash (that the camera was expecting) never happens - the photo will be massively underexposed.

Why, because that pre-flash was just that - pre the shutter movement. So, no light from it entered the shutter.

All it did was tell the flash how strong it needs to be.

Scotty

[Scotty72]

Well, in fairness. It is very difficult to get your head around modern flash technology.

Sometimes, I know what the flash is doing but am not sure how it is done - thus my questions earlier in the thread.

I know that the more I learn about flashes, the less I know about it.