580ex ii and 7D

[Trevoreast]

Re: 580ex ii and 7D

I have just tried it on my 60D, and can confirm that the built-in flash has absolutely no effect on the image!

I can only really talk about the 7D & 580ex2.
Are you able to fire the built in flash straight at a reflective surface / subject and not see the flash reflection in the image ?

Trev

[S_J_P]

580ex ii and 7D

I stand corrected! Contrary to what I've read, and what I believed, there is indeed a small (but significant) input from the on-camera flash in master mode. How has that fact been missed all this time?

[Trevoreast]

Re: 580ex ii and 7D

The pre-flash, setting the exposure, will fire before the shutter opens and only the external 'guns flash will impact the scene (unless I'm missing something!)

IF there's just a pre-flash that occurs before the shutter opens
Change the flash to manual mode, and observe how built in flash still fires. :-)

Trev

[Trevoreast]

Re: 580ex ii and 7D

Hi Steve sorry I posted before seeing your last reply.

This system is usuable but maybe canon didn't think of it as a professional tool or even a rival to the ste2
More of a "bone" thrown to mid range camera users like myself.
I have no doubt poeple will get great results using this setup.

Trev

[S_J_P]

580ex ii and 7D

I guess that due to the way the system operates (pre-flash to set exposure, then a "trigger" flash) there must be some form of light output from the built-in flash once the shutter is open otherwise the system wouldn't be able to sync the external slave 'gun as shutter lag varies by conditions and camera. I'd always presumed that the lack of second curtain sync with wireless was to do with the pre/trigger impacting upon the image, but I'd never considered that even standard first curtain sync was affected too.

This feature of Canon's wireless system has explained some peculiar lighting effects I saw when doing some water drop photography though (using wireless), and vindicates the use of a TTL cord rather than relying on wireless.

Maybe those Yongnuo 622c radio-triggers I've had my eye on for a while now are more useful than I'd thought!

[David Morison]

Re: 580ex ii and 7D

With the Metz MS1 Macroflash a clip is supplied which goes over the on board flash to dramatically mask the output but still enough to set off the macro unit. I don't know whether this will work with other flashes but I'll give it a try.

David

[maasg]

Re: 580ex ii and 7D

For E-TTL to work, two flash pulses from the master flash are needed:

When you fully press the shutter release button (or the FEL button), the master unit will send an encoded pre-flash burst that will indicate the slaves to also fire a pre-flash for the camera to determine the correct flash exposure. This happens before the shutter actually opens, so no light from the pre-flash is contributed to the exposure.

Then, when the actual exposure starts, the master needs to tell the remote flashes to fire. That beam of light is of very low power, but it will contribute to the exposure. If you are using high ISO settings or you have highly reflective materials in front of you, some of that light will become part of the final image.

If you want to fully eliminate the contribution from the built-in flash, you could cover it with an IR filter. That's what the ST-E2 actually does.

In the film era, IR filters for this purpose were easy to come by... you just needed a piece of exposed and developed slide film for that. Nowadays you might need to find a store that still stocks Kodak Wratten 89 filters.

I might still have some plastic IR filters somewhere in the basement. If you're still having issues with this, drop me a line and I'll see if I can get you a piece of IR filter.

-kr, Gerard.