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FORUMS General Gear Talk Flash and Studio Lighting 
Thread started 02 Feb 2012 (Thursday) 10:20
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E-TTL Vagaries

 
oldvultureface
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Feb 02, 2012 10:20 |  #1

After purchasing a 580EX II, I've been experimenting with E-TTL in both auto and manual mode. The power difference (in pure manual mode, not E-TTL) between the 430EX II and 580 is about one stop. When I fire the two with dumb radio triggers, I have to set the 580, for instance, to 1/64 and the 430 1/32 to get equal shadows on both sides of a subject.

However, when triggered through Canon's wireless setup, E-TTL seems to compensate for the power difference with both auto ratios and manual power settings. If I set 1/16 power on both flashes, I get equal shadows on both sides of the subject when I would expect to see a difference because of the differing power outputs.

Is this my imagination or does Canon correct for the power discrepancy between the two flashes?

The setup (not my doll :)):

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Feb 02, 2012 17:54 |  #2

You can't have ETTL and manual activated at the same time. If you clarify what you're doing people may be able to help. Do you mean multiple wireless flash using the Canon system, set to manual power control?

AFAIK manual is manual.


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oldvultureface
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Feb 02, 2012 18:59 |  #3

tim wrote in post #13815171 (external link)
Do you mean multiple wireless flash using the Canon system, set to manual power control?

Correct. However, Canon's 'manual' wireless system does not appear to be completely manual. There is, of course, a control preflash to set up the slaves before the picture is taken even in manual mode. And Canon's system seems to be compensating for the difference in power (within manufacturing tolerances and my tape measuring accuracy) between the 430 and 580 flash.

E-TTL 1:1 ratio:

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Canon wireless manual, both flashes (580 camera left, 430 camera right) set to 1/32 power. This is what gets me. The 580 on the left, being more powerful, should produce a noticeably darker shadow to the right of the subject:

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Totally manual. Both flashes set to 1/64 power and fired by dumb radio triggers. Now one clearly sees the difference in the output between the two flashes at the same power setting. Note also the difference in white balance (set to 'flash' for all pictures) between the two Canon controlled pictures and this one where the camera was not aware a flash was being used. That I would expect as Canon claims white balance is modified as needed when using a Canon flash and 'flash' or 'auto' white balance is selected:

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oldvultureface
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Feb 02, 2012 19:06 |  #4

tim wrote in post #13815171 (external link)
You can't have ETTL and manual activated at the same time.

You can but that's not what concerns me.

Press the mode button on a flash in E-TTL slave mode for several seconds 'til 'M' flashes. Then set the output manually. It will fire at the manual setting while the other slaves fire in E-TTL.




  
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tim
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Feb 02, 2012 19:14 |  #5

ETTL is automatic metering. I don't know the name for the wireless system built into Canon speedlites.


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oldvultureface
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Feb 02, 2012 19:40 as a reply to  @ tim's post |  #6

What I'm wondering is if anyone else has noticed, with flashes of differing power, that Canon's wireless system is compensating for that difference with regard to ratios and also manual output.




  
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oldvultureface
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Feb 02, 2012 19:55 |  #7

tim wrote in post #13815587 (external link)
I don't know the name for the wireless system built into Canon speedlites.

Sorry for the confusion. Until now, I considered Canon's wireless manual implementation as a subset of its E-TTL system. :confused:




  
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mabviper
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Feb 03, 2012 15:16 as a reply to  @ oldvultureface's post |  #8

Canon flashes, when placed into wireless slave mode, will always get its operating mode from the flash master. It can be from the camera (7D) or mounted hotshoe flash (580ex). Whatever setting you put into the flashes will disappear once it gets the preflash commands from the master.

For example, in your tests, if you place both of them as slaves and changed their modes to Manual after you take a shot from your 7D, the camera will change flash modes to wireless E-TTL. If you look at your flashes after the shot, they should both display E-TTL as their operating modes.

You can try wireless manual mode by changing the master flash settings in the 7D to manual instead of E-TTL. After that, you need to change the flash set (A, B or C) on each flash. You can then modify the flash power of each flash set in the 7D flash menu.

Hope it helps ^^


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Feb 03, 2012 17:59 |  #9

mabviper wrote in post #13820367 (external link)
Canon flashes, when placed into wireless slave mode, will always get its operating mode from the flash master. It can be from the camera (7D) or mounted hotshoe flash (580ex). Whatever setting you put into the flashes will disappear once it gets the preflash commands from the master.

For example, in your tests, if you place both of them as slaves and changed their modes to Manual after you take a shot from your 7D, the camera will change flash modes to wireless E-TTL. If you look at your flashes after the shot, they should both display E-TTL as their operating modes.

You can try wireless manual mode by changing the master flash settings in the 7D to manual instead of E-TTL. After that, you need to change the flash set (A, B or C) on each flash. You can then modify the flash power of each flash set in the 7D flash menu.

Hope it helps ^^

I do understand all that. :) I operated the flashes for the first two pictures from the 7D's menu. First picture was A:B with a ratio of 1:1, A being the 580 camera left, B being the 430 camera right. The second picture was wireless manual, (A,B,C), setting A and B manually to 1/32 power. The last picture was radio triggered with flashes set at 1/64. Note also, Canon manual needed 1/32 and total manual needed 1/64 for virtually identical exposures.

This was and still is my question:

oldvultureface wrote in post #13815696 (external link)
What I'm wondering is if anyone else has noticed, with flashes of differing power, that Canon's wireless system is compensating for that difference with regard to ratios and also manual output.




  
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René ­ Damkot
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Feb 05, 2012 09:04 |  #10

Lighting is totally different in the first two and the last image: Looks like the on camera flash also lit the scene in the first two.


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Feb 05, 2012 10:35 |  #11

mabviper wrote in post #13820367 (external link)
Canon flashes, when placed into wireless slave mode, will always get its operating mode from the flash master. It can be from the camera (7D) or mounted hotshoe flash (580ex). Whatever setting you put into the flashes will disappear once it gets the preflash commands from the master.

For example, in your tests, if you place both of them as slaves and changed their modes to Manual after you take a shot from your 7D, the camera will change flash modes to wireless E-TTL. If you look at your flashes after the shot, they should both display E-TTL as their operating modes.

You can try wireless manual mode by changing the master flash settings in the 7D to manual instead of E-TTL. After that, you need to change the flash set (A, B or C) on each flash. You can then modify the flash power of each flash set in the 7D flash menu.

Hope it helps ^^

You can force a slave flash to manual and have it stay there when it is part of an eTTl setup. You get your slave all setup as normal with the correct channel and group numbers. Then press and hold the mode button on the slave flash until the M indicator starts flashing. Then press the set button. The slave is now locked into manual mode and you have to adjust its power from the back panel of the flash. The only place that I have found this documented is in Syl Arena's book, Speedliters Handbook. He calls it Free-Agent Wireless.

Also in your example, I am pretty sure that if you start your slaves out in slave mode with manual selected, they will not respond to the master. I will have to confirm that later. It does work the other way though. If they are in eTTL mode and you change the master to manual, after the next shot the slaves will display manual.

Edit: I did a test with my 7d and 580ex and if the 580ex is in manual mode when you move the switch to slave it changes to eTTL mode and you cannot change it back with out doing the Free-Agent method described above.



  
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mabviper
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Feb 05, 2012 10:48 |  #12

dedsen wrote in post #13829287 (external link)
You can force a slave flash to manual and have it stay there when it is part of an eTTl setup. You get your slave all setup as normal with the correct channel and group numbers. Then press and hold the mode button on the slave flash until the M indicator starts flashing. Then press the set button. The slave is now locked into manual mode and you have to adjust its power from the back panel of the flash. The only place that I have found this documented is in Syl Arena's book, Speedliters Handbook. He calls it Free-Agent Wireless.

Also in your example, I am pretty sure that if you start your slaves out in slave mode with manual selected, they will not respond to the master. I will have to confirm that later. It does work the other way though. If they are in eTTL mode and you change the master to manual, after the next shot the slaves will display manual.

Wow, I didn't know about that you can force a canon flash into manual mode with wireless ettl. It's kinda like an optical trigger for wireless ettl. Thanks for that info. ^^


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Feb 05, 2012 11:14 |  #13

I did not know about it before reading Syl's book. I can see where it would be handy if you had more than 3 flashes that you needed at different powers. It allows you to have unlimited groups at different power settings. The down side is you have to go to each flash to change the power settings.



  
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oldvultureface
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Feb 05, 2012 11:24 |  #14

René Damkot wrote in post #13828845 (external link)
Looks like the on camera flash also lit the scene in the first two.

The popup master was turned off in the wireless menu. What little light it would contribute in that configuration would not be visible (except in a mirror) shooting at ISO 100 and f/11.

René Damkot wrote in post #13828845 (external link)
Lighting is totally different in the first two and the last image ...

Aside from the white balance (explained with the last picture in post #3), that's my point. The first two images do not reflect the difference in power between the 430 and 580 (approximately one stop). Canon's system seems to be attenuating one of the flashes to make both appear to be the same power. The last image, fired by simple radio triggers, does show the difference between the 430 and 580 both set to 1/64 power.




  
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Feb 08, 2012 19:11 |  #15

oldvultureface wrote in post #13815545 (external link)
You can but that's not what concerns me.

Press the mode button on a flash in E-TTL slave mode for several seconds 'til 'M' flashes. Then set the output manually. It will fire at the manual setting while the other slaves fire in E-TTL.

It uses the "E-TTL system" (whatever it's called) to trigger them when it's in Manual but it doesn't control their output when in Manual. When in E-TTL Auto it controls both triggering and output as ratios (1:1, 1:2, 1:4, etc). It's an all or nothing system. They're either all E-TTL Auto or all E-TTL Manual. The reason both shadows are equal in the Auto shot is your ratio is set as 1:1 = telling it to fire both at the same power level. 1:1 doesn't mean each flash fires at its max capability, and it has nothing to do with the manual output level set on the flash.


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