Controlling multiple flashes

[chairmnofthboard]

How do I control the flash output of my slave flashes?

Can I control each flash power output individually?

I use my 580 as master and 430/420 as slaves.

And yes, I did a search.

[apersson850]

Search the user's manual for the 580 EX (II). It will tell you.

But basically the answer is yes. You can split up the slaves in three groups, A, B and C, and these three groups can be controlled individually, in different ways, depending upon how you set up the master.

[CliveyBoy]

You do mean 580EXII, and not 580EX as your post said?

Put the 580EXII on camera, and set the remote slaves to E-TTL and Slave. The slaves should be set to A or B or C and channel 1.

Use the 50D menu to select Flash Control/External flash func. setting.

Set Flash Mode to Manual Flash. Then cusror down to select Wireless Set.

Enable Wireless Func. and Master Flash.

Select Firing Group A:B C - as the flash is set to Manual mode, each group (A, B, C) can have its power level set.

Fire a test shot. Check the slaves - they should now display the settings as conveyed by the Master. After the initial setup, there should be no need to touch the slaves, unless they are out of range.

[PacAce]

You do mean 580EXII, and not 580EX as your post said?

Put the 580EXII on camera, and set the remote slaves to E-TTL and Slave. The slaves should be set to A or B or C and channel 1.

Use the 50D menu to select Flash Control/External flash func. setting.

Set Flash Mode to Manual Flash. Then cusror down to select Wireless Set.

Enable Wireless Func. and Master Flash.

Select Firing Group A:B C - as the flash is set to Manual mode, each group (A, B, C) can have its power level set.

Fire a test shot. Check the slaves - they should now display the settings as conveyed by the Master. After the initial setup, there should be no need to touch the slaves, unless they are out of range.
The 430EX can be set to manual slave mode but the 420EX cannot so it'll have to be removed from the wireless configuration if manual control is desired.

[agv8or]

To answer your question "How do I control the flash output of my slave flashes?".


First make sure your slaves are configured properly. 1. Set to slave, 2. Proper channel selected 1-4, 3. The proper group A, B or C, and 4. Make sure to manually set your zoom at each slave flash as the master will not do this.

First it must be noted that the mode set in your master flash will be the mode that your master flash controls your slave in unless you override each slave as mentioned below. In the wireless configuration your master can be set to operate wirelessly in either E-TTL or Manual modes. I have never used Multi mode let alone Multi wireless so I will leave that for others to comment on.


To control your slaves in the Manual mode Wireless configuration:
I will echo what PacAce stated in that the 420EX is not capable of manual flash operation so there for cannot be used in a wireless config manual mode operation but the 430EX can be so if you wish to you can control the 430EX, in the wireless config manual mode, here are the two ways of doing so.

1. Directly from the master flash by entering a manual power setting into the group in which the slave flash is placed. So in other words if your 430EX is set to group A go into the master and set the desired manual flash setting in group A.

2. As I mentioned above each slave can be overriden manually to where the master flash only triggers that slave and all settings are manually entered into the slave at the slave. Go to your slave flash and hold down the mode button for two seconds until the M is flashing. (This removes that individual flash from any slave groups but it still allows it to be fired by the master flash.) When the M is flashing the flash is now in the Manual mode. Enter a manual power setting directly into this flash just as if it were a stand alone flash in the normal configuration. This procedure can also be used even if the master flash is set to the E-TTL mode (something to bear in mind when we discuss E-TTL wireless operation below). You can also set that slave to operate in the Multi mode as well by pushing the mode button one more time after the M starts flashing.

Now when operating in the E-TTL mode while in the wireless configuration:

Again make sure your master flash is set to the proper mode in this case to E-TTL.

You control your slaves in E-TTL wireless via Ratios and FEC (Flash Exposure Compensation). Remember when operating in E-TTL your camera is doing the metering and controlling the flash outputs based on its readings. You can change this exposure + or - 3 stops by changing the FEC.

If you have one or more slaves but did not turn on "Ratio A:B or Ratio A:B C" in your master, even if those slaves are set to different groups, then the slave(s) output will be controlled directly by FEC and you will have no individual control over any of the groups.

If you have Ratio A:B or Ratio A:B C turned on and you are using two flash units in the A and B groups then you change the flash outputs of these two groups by changing the Ratio between the A and B groups . When you change the Ratio between the A and B groups you raise the value of one group while lowering the value of the other group. If you get the desired Ratio between the A and B groups about right but the overall image is too dark or too light then you can change the overall exposure with FEC which is global and controls flash exposure for groups A and B ( as well as C ) equally.

If you add a third flash and place it in the C group then the C group (Ratio A:B C must be turned on) is adjusted as an FEC in relation to the overall exposure obtained by the A and B flash units. The C group was designed to act as a background light and when you think of background light you think of it's value in relation to the exposure of your subject. Lets say you have an exposure of f8 on your subject and you want the background to be darker by a stop then you would want a reading of f5.6 on your background.

What group C does (the camera does, not the actual flash in group C) is looks at the overall exposure obtained by groups A and B and then fires at whatever FEC value you entered. If you entered for group C to fire at -1 then it would fire to illuminate whatever it is pointed at to be 1 stop under the exposure that was obtained by groups A and B.

This is a pretty simplified explaination of the C group as well as the E-TTL mode in the wireless configuration. There is more that goes on than what I described but, when you think of it in the context I outlined then you will have better control over it and after all that is the primary question you asked.

[CliveyBoy]

Thanks, Leo for noting the limitation of the 420EX.

As I explained above, the camera menus make the settings very clear and simple, and you can then set the 1/1 to 1/64 etc power levels for each group A, B and C.

This enables you to control the flash output of the slaves - and all from the camera.

Or, you can use the camera menus to set the A:B ratios and FEC on group C, but that leaves the camera in control of the flash output rather than the user.

[Titus213]

You can do the same thing with the 580EX, it just doesn't work through the camera menu as I understand it.

[CliveyBoy]

And with the 550EX, but the inability to use the camera menus is a big deal. This newish capability seems to be ignored and underrated as much as any of the new technologies of the last 7 years.

The old hands stick with what they are competent at, and newcomers get the benefit of the new technology "because they know no better". Finally the old hands catch up and wonder why they didn't adopt (adapt?) earlier.

I like the full words in the menus - eg for flash custom functions. I especially like the size of the information - I need to find my reading glasses and put them on to read the flash's lcd, then take them off for the rest of the camera work.

The inter-dependent logic of various settings is also abundantly clear, and for a new flash user this can be the best way to learn what is involved, and then go onto the flash buttons after understanding has been gained. This is why I suggested that the OP uses this route to understanding.

[apersson850]

On the 7D, Canon has finally taken yet another step along the route of multiple flash control, as the 7D can use the internal flash as a master as well.
It's actually a bit more advanced than what's possible if you use a 580 EX II as a master, since the internal flash works in a group by itself, not always in group A, as an external master does.
The menu system for flash setup is also a tad more comprehensive on the 7D. If you are doing studio work so you can have a USB cable plugged in, or use the horribly expensive WFT-E5, you can use a netbook tethered to the 7D, and then set the flash setup on the computer. If you are taking photos of a recurring kind, you can store your flash setup in a file, for later retreival and reloading into the camera.

[chairmnofthboard]

You do mean 580EXII, and not 580EX as your post said?

Put the 580EXII on camera, and set the remote slaves to E-TTL and Slave. The slaves should be set to A or B or C and channel 1.

Use the 50D menu to select Flash Control/External flash func. setting.

Set Flash Mode to Manual Flash. Then cusror down to select Wireless Set.

Enable Wireless Func. and Master Flash.

Select Firing Group A:B C - as the flash is set to Manual mode, each group (A, B, C) can have its power level set.

Fire a test shot. Check the slaves - they should now display the settings as conveyed by the Master. After the initial setup, there should be no need to touch the slaves, unless they are out of range.

I'm sorry, it's 580ex II.

I can't find my owners manual, that's why I'm asking.

Man this is really confusing.

[PacAce]

I'm sorry, it's 580ex II.

I can't find my owners manual, that's why I'm asking.

Man this is really confusing.
You can download the 580EX manual from here:

http://www.usa.canon.com/consumer/controller?act=ModelInfoAct&fcategoryid=141&modelid=14998#DownloadDetailAct

[apersson850]

Man this is really confusing.I think it will be easier if you state clearly if you want to control the flashes' relative strength in E-TTL, or their absolute power using manual power setting?

[chairmnofthboard]

I think it will be easier if you state clearly if you want to control the flashes' relative strength in E-TTL, or their absolute power using manual power setting?

Now I am even more confused. I figured out how to get the flashes to have different power levels. But I am confused with the A:B control, C control, FEC on the flash and FEC on the camera.

I can get the effect I want, but I doubt I using these features correctly.

[apersson850]

When you write "different power levels", I assume that's when using manual settings? So that you can set 1/8 or 1/32 power, for example. Right?

For the rest, I suggest you start using only two flashes, in groups A and B, and play with different ratios between them to learn what happens.
Then add some FEC on the camera, to see what happens.
Finally, add group C, aimed at the background only, and adjust the separate FEC for that flash to see what happens.

Note that the 7D, if using the internal flash as a master, handles this issue with the different FEC settings slightly differently.

[bobbyz]

OP, more info about canon flash over at Chuck's website:

http://super.nova.org/DPR/Canon/CanonRatios/

[chairmnofthboard]

I tried playing around with them in M, however as mentioned my 420ex doesn't work in M, and I couldn't control the flashes well. I am using them in ETTL.

I really appreciate the help everyone.

When you write "different power levels", I assume that's when using manual settings? So that you can set 1/8 or 1/32 power, for example. Right?

For the rest, I suggest you start using only two flashes, in groups A and B, and play with different ratios between them to learn what happens.
Then add some FEC on the camera, to see what happens.
Finally, add group C, aimed at the background only, and adjust the separate FEC for that flash to see what happens.

Note that the 7D, if using the internal flash as a master, handles this issue with the different FEC settings slightly differently.