7d: Pop-up flash master/slave works...check

Started Oct 1, 2009 | Discussions
Julio Veteran Member • Posts: 4,886
7d: Pop-up flash master/slave works...check

Just a couple of quick 2-flash set-up shots.

Pop-up set-up to not fire and control a 550EX on the left (Group B) and a 420EX on the right (Group C.)

First shot is Group B only--notice that even though the distance was fairly short--about 4 feet--and the pop-up uses visible light to send it's commands, it doesn't contribute to the exposure.

The second one is as above but with C providing -3EV fill. When you have 3 flash groups, Group C's exposure is controled by it's own separate +/- 3 EV - 3 is equivalent to a B:C 8:1 ratio I believe.

And for trivia fans, yes that's an Ed Jovanoski bobblehead

-- hide signature --
ScratchDisk Veteran Member • Posts: 3,750
Re: 7d: Pop-up flash master/slave works...check

Hi, And thanks!

Very interested especially if the 'no contribution' (photo 1) from the built-in master is an absolute comment. If that is strictly correct then Canon have delivered a flash solution that in one tiny regard is superior to Nikon's equivalent. That may have removed one reason to consider trying Nikon's SG-3IR filter on a 7D - something I requested here a couple of days ago. The other reason remains - namely making the pre-flash 'stealthy'. I don't suppose you have access to a SG-3IR do you?

Either way, thanks for your post.

(We need to get someone to try Radiopopper's PX Tx driven from a 7D built-in!)

 ScratchDisk's gear list:ScratchDisk's gear list
Canon EOS M5 Canon EOS 5D Mark III Canon EOS 90D
Paul Feng Regular Member • Posts: 231
Nice lighting, but...

...your subject seems a little stiff.

First! (?)

(Sorry)

OP Julio Veteran Member • Posts: 4,886
This is what the pop-up would have done

I was shooting slightly from above and the 2 flash units were slightly below. You can see that the top of his helmet was in deep shadow in both photos above. The pop-up would have filled that, at least a tiny bit, if its light had any effect.

Mind you, to be absolutely sure, I should reshoot using a high ISO and large aperture with the flash facing the background and compare that with a pure ambient light no-flash shot at the same setting. I might do that when I get some time later today.

This is a pop-up flash shot from the same position:

-- hide signature --
ScratchDisk Veteran Member • Posts: 3,750
Re: 7d: Pop-up flash master/slave works...check

..in fact Julio,
I’m intrigued.

With other Canon masters there is in fact a 'trigger-flash'. (I'm not referring to ‘pre-flash’, nor ‘capture-flash’, but ‘trigger-flash’.) It’s extremely weak – weaker than the Nikon equivalent. IOW with the master set to taking/capture flash ‘disabled’ there is still a minute amount of master flash visible in the capture. With other Canon masters the only reliable way to see this, is to make the camera capture itself, complete with master flash tube, in a mirror. Set master to capture-flash ‘disabled’, don’t have a live slave anywhere near, and closely examine the (very underexposed) capture. With your new 'built-in' 7D master, is there absolutely, positively NO light coming from the built-in master flash tube, in such a mirror based capture?
If so, that is a first.

Thank you for humouring a strobo-nerd! Cheers
(Sorry, this post clashed with your reply above. Tx!)

 ScratchDisk's gear list:ScratchDisk's gear list
Canon EOS M5 Canon EOS 5D Mark III Canon EOS 90D
OP Julio Veteran Member • Posts: 4,886
Re: 7d: Pop-up flash master/slave works...check

ScratchDisk wrote:

..in fact Julio,
I’m intrigued.

With other Canon masters there is in fact a 'trigger-flash'. (I'm not referring to ‘pre-flash’, nor ‘capture-flash’, but ‘trigger-flash’.) It’s extremely weak – weaker than the Nikon equivalent. IOW with the master set to taking/capture flash ‘disabled’ there is still a minute amount of master flash visible in the capture. With other Canon masters the only reliable way to see this, is to make the camera capture itself, complete with master flash tube, in a mirror. Set master to capture-flash ‘disabled’, don’t have a live slave anywhere near, and closely examine the (very underexposed) capture. With your new 'built-in' 7D master, is there absolutely, positively NO light coming from the built-in master flash tube, in such a mirror based capture?
If so, that is a first.

I'll check that out when I get sometime. But I can tell you that the pop-up does fire to communicate the comands. And I assume that it's not doing it with the pre-flash in ETTL mode since it also can conrol remote flashes and optical slaves in manual mode--it would need to do it during the actual flash for that. I'm sure the "flash" will be visible in the mirror if I do what you suggest.

The real question is how (in)significant the light output is. So far so good, but I'll try it in a more extreme situation--closer to the subject, etc.

-- hide signature --
ScratchDisk Veteran Member • Posts: 3,750
Re: 7d: Pop-up flash master/slave works...check

Hi Julio,

First thanks again for your info, it's going to be a little while before I can justify buying a 7D - but I am drooling as you can probably tell.
You are a little off target with this comment;

"..and I assume that it's not doing it with the pre-flash in ETTL mode since it also can conrol remote flashes and optical slaves in manual mode--it would need to do it during the actual flash for that.."
The best Canon info on that issue is on page 2 of this Canon site;
http://cpn.canon-europe.com/content/infobank/flash/wireless_flash.do#container

..it's well worth a quick read, including the diagramic representation of 'pre-flash'.

Under both ETTL/Autoflash and Canon Manual Wireless all of the control (except the actual triggering) is handled within the 'pre-flash exchange'. In fact for Canon Manual Wireless, it's not strictly an exchange because the pre-flash communication is only one-way. HTH
Cheers

 ScratchDisk's gear list:ScratchDisk's gear list
Canon EOS M5 Canon EOS 5D Mark III Canon EOS 90D
Jehuty Regular Member • Posts: 137
Re: 7d: Pop-up flash master/slave works...check

you know, all you have to do is pull the flashes out of the room that your shooting in. i have the 7d and i did the same thing. i turned out the lights, fired a couple of shots with my 580 and 430 EXIIs and then pulled them out to be certain no light was coming from the on board flash. i took the shoot and the image was completely black. i was about three feet away from my subject so if there was an effect from the on board flash it would have showed up for sure. we can rule out this being a problem.

ScratchDisk Veteran Member • Posts: 3,750
Re: 7d: Pop-up flash master/slave works...check

Thanks, ....and I agree that for 99% of the time your test does indicate that there will not 'be a problem'. You may be aware that with the equivalent Nikon setup using their pop-up as a controller, there is a minor issue. It only really manifests at close range with highly reflective subjects etc - it's one of the reasons why Nikon have the SG-3IR filter.

It seems as if Canon have really tried quite hard to get the flash game as good as they could with the 7D. Thanks

 ScratchDisk's gear list:ScratchDisk's gear list
Canon EOS M5 Canon EOS 5D Mark III Canon EOS 90D
SteveDude Senior Member • Posts: 2,485
The significance of the trigger-flash light will be iso-dependent

Since the trigger flash is fixed output, you should be able to see a ton more effect shooting a flash shot at higher isos than lower isos. Just like ambient light mixes in much more at iso3200 than iso100.

It might be interesting to have you shoot a trigger-only shot at a few different ISOs (maybe even an extreme like 6400) to see how much it lights up the subject.

Steve

-- hide signature --

My galleries are at http://www.GrillosView.com , Equipment on profile page

Thefo Forum Member • Posts: 81
Re: 7d: Pop-up flash master/slave works...check

Thanks Julio, that is excellent news. Now I want this camera even more since the onboard master feature interests me greatly.

Regards,
--
Heath
40D, 17-40F4L, 70-200F4L, 50 EF1.4, 300F4L, 430EX

chanandrew Regular Member • Posts: 355
Re: 7d: Pop-up flash master/slave works...check

nice sample!

-- hide signature --
xxD Contributing Member • Posts: 726
Oooh. I like it (nt)
n/t
Keyboard shortcuts:
FForum MMy threads