Sorry for the cross post, flash info needed.

[Mr Felix]

I am reading a lot about the flashes and the different types.

I am still not 100% sure if the 550D is E-TTL A-TTL or any TTL.

My speedlight (in other post/thread) is probably tooooo old, but I am sure it used to work with TTL on my old AE1-P. But that is "so yesterday" is seems.

Anyway, reading and looking there are those kind of flashes then there are the FP (high speed) flashes which work at ANY speed.

I have also read about cyncing the flah to the curtains. First, second or both.

First curtain flashes when the shutter opens.

Second curtain fires the flash just before the shutter closes.

Both, does two flashes. One when the shutter opens and one when it closes.


I have also read where you open the shutter, fire the flash and hold the shutter open for 'x' seconds after that. It was called "Dragging the flash" but not sure if that is THE term and/or if/how I could do it on the 550D.



Anyway, this "FP" system sounds interesting.
Other than setting up lights everywhere they are needed and leaving them on for how ever long it takes, is a lot of effort/energy.

CAN/COULD I set up a system using the FP signal to "fire" the flashes/lights when the shutter button is pressed?

That way I can do what I want, set the lights (rear ones, side, etc.) have anothe button to activate the lights so I can see what I will get, then when happy, "Click" take the image and have the lights flash then.


This would probably mean getting a hot-shoe thing to connect to the camera's flash connection and build some electronics. Not a problem - unelss it involves extreme building/design.

But if they are only discreet signals/voltages - not an entire sequence of pulses - then it shouldn't be that difficult.


Anyone every done this?

[Clubmanmc]

sorry to be blunt but you have added tooo many questions to answer in a short short time...

the 550D is a E-TTL camer, which stands for Electronic Thru The Lens Metering, it does this by emmitting a pre-flash an instant before the shutter opens, hence the timing between them is so small that you wouldnt see the difference...

as for the 2 end sof the curtain synchnorization, yes it flashes as it opens or as it closes, the best way to see this is to set your Tv to 1 sec, you will see the preflash and then the flash go off just before the curtain closes.

the high speed flash function works by burning the flash for longer than the usual, as the 550D and all canon EOS cameras have a 2 focal plane shutter, there is effectively a slit open as the cmos is being exposed, so if it flashed normally the flash would only be visible in one small section, the flash will then light for as long as the "cylce" of the two shutters takes to traverse the focal plane.... even though the Tv is only 1/500th of a sec, the time it takes to travel the length of the focal plane shutter is longer, hence the flash burns for the entire time the two shutters are working...

this will use more battery power..

as for the setup... i am unsuure as to what you really want to achieve... maybe some wireless triggers are what your after...

M

[Mr Felix]

What I want to do is set up some electronics so when I press the shutter button I can have a circuit to drive lights.
Any size/type/voltage, as there will be isolation between the camera and the "flashes".

Isolation as in electrical. I would use wither an opto coupling, semiconductor, or similar.

[kiwi]

What sort of lights ?

Speedlghts dont really have the ability to have what's called a modelling light
Continous lights have the benefit of getting what you are seeing, you don't need to trigger either
Strives or studio lights usually have a modelling mode so you can test positioning but not at full power and there are several ways of triggering them...radio wireless, sync cables and optical

A couple of speed lights is easiest

[MarkChap]

If you use radio triggers, there is no connection with the camera at all, thus isolating the camera from any voltage due to the flashes.
If you are using high powered, read older flashes with high trigger voltage, you will most likely fry the electronics in the receivers.
What you will need then is a Safe Sync (http://www.weinproducts.com/safesyncs.htm) between each flash and the trigger/receiver.
If you google the term Safe Sync, you will be provided with plenty of reading and even multiple DIY offerings.

[Mr Felix]

Well, the actual flash part is still not determined.

I was more interested in constructing the interface which detects the shutter being pressed. The speedlight - in the hotshoe - receives a signal from the camera when you press the shutter button.

What I am wanting to build that part which detects the signal. From there, I can build radio/wireless signals etc to control what ever.


Actually what would also be nice to learn - but I think I am at the wrong end of the camera - is to also build a circuit which will go from something to tell the camera to take a image, but that may not be acceptable to ask that here.

This is more for flashes rather than making the flash happen.

Thanks shall look at safesync.

[Mr Felix]

Looked, thanks.

Yeah, but they are "pre-built" things. I am wanting to learn the signals sent from the camera to the flash, and vice versa.