430ex as main (wireless), 580ex as fill

Ok I'm confused, if you asked my partner she would say this is normal behaviour

I'm intending to use a 430EX with silver umbrella off camera (slave) and use the 580EX on camera (master).
What I'm trying to achieve is for the 430EX to be my main light and for the 580EX to only give me the fill.

I've tried ETTL but and manual but for some unknown reason cannot work out how to alter the ratios. I'm hoping to achieve f8 with the 430 and around f5.6 with the 580.

Any help would be greatly appreciated. If anyone knows of any websites this would be much appreciated also. I've tried the strobist site but it doesn't have anything on how to alter the ratios between the 430 and 580 EX's

Thanks again all

Ok I'm no longer confused (about the flash that is )

Set the 430EX to channel 1 and unit B, set 580EX to channel 1 and unit A. Then activated the ratio option and I was set.

Goes to show that thinking about it doesn't always help. Writing it down makes it clear.

I can't believe how simple it was, yet the brain didn't grasp the idea.
I think this is what they refer to as a Homer moment DOH

It's amazing how, after posting what seams a simple question, the panic sets in and you work it out yourself! Have fun.

Thornfield wrote in post #2694404
Ok I'm no longer confused (about the flash that is )

Set the 430EX to channel 1 and unit B, set 580EX to channel 1 and unit A. Then activated the ratio option and I was set.

Goes to show that thinking about it doesn't always help. Writing it down makes it clear.

I can't believe how simple it was, yet the brain didn't grasp the idea.
I think this is what they refer to as a Homer moment DOH

When you WANT a 3:1 lighting ratio with the setup you've described, which basically means that the Main is almost one stop brighter than the Fill, you must choose 1:3 on the ratio controls of the 580EX. And of course this applys to any ratio you choose. If you actually pick 3:1 the Fill will be brigher than the Main. I know that this sounds weird but that's the way it goes!

DaveG wrote in post #2695118
When you WANT a 3:1 lighting ratio with the setup you've described, which basically means that the Main is almost one stop brighter than the Fill, you must choose 1:3 on the ratio controls of the 580EX. And of course this applys to any ratio you choose. If you actually pick 3:1 the Fill will be brigher than the Main. I know that this sounds weird but that's the way it goes!

Only if his main is on A. It goes A:B:C so if the 580EX is on A and to be used as fill he wants 1:3.

cdi-ink.com wrote in post #2695147
Only if his main is on A. It goes A:B:C so if the 580EX is on A and to be used as fill he wants 1:3.

Except that you can't use the on camera Master/Fill as a B group flash. It must be an A Group.

DaveG wrote in post #2695118
When you WANT a 3:1 lighting ratio with the setup you've described, which basically means that the Main is almost one stop brighter than the Fill, you must choose 1:3 on the ratio controls of the 580EX. And of course this applys to any ratio you choose. If you actually pick 3:1 the Fill will be brigher than the Main. I know that this sounds weird but that's the way it goes!

The OP used a lighting example of f/8 for the main and f/5.6 for the fill. That's a one stop difference between the main and the fill light. To get a one stop difference in lighting ratio, with the master as the fill and the slave as the main, a ratio of 1:2 needs to be set, not 1:3 which will give a difference of one and a half stops.

PacAce wrote in post #2696166
The OP used a lighting example of f/8 for the main and f/5.6 for the fill. That's a one stop difference between the main and the fill light. To get a one stop difference in lighting ratio, with the master as the fill and the slave as the main, a ratio of 1:2 needs to be set, not 1:3 which will give a difference of one and a half stops.

No that's not the way ratios are calculated. A one stop difference is 3:1.

DaveG wrote in post #2696411
No that's not the way ratios are calculated. A one stop difference is 3:1.

I guess it all depends on what book you are reading but as far as the EX flashes is concerned, 1:2 is what give you a one stop difference.

Maybe but if you calculate manual strobes to give you a 3:1 lighting ratio then the difference between Main and Fill is almost one stop. If 1:2 on the Canon (which is really 2:1) is that same almost one stop, then Canon has gotten it wrong.

By the way how can you determine what exactly any Canon E-TTL flash is actually outputting? My flash meter won't work with E-TTL as the first instructional pulse will set it off.

DaveG wrote in post #2697793
Maybe but if you calculate manual strobes to give you a 3:1 lighting ratio then the difference between Main and Fill is almost one stop. If 1:2 on the Canon (which is really 2:1) is that same almost one stop, then Canon has gotten it wrong.

By the way how can you determine what exactly any Canon E-TTL flash is actually outputting? My flash meter won't work with E-TTL as the first instructional pulse will set it off.

This really has nothing to do with whether Canon got it right or not. It's all about what the markings on the flash is supposed to mean and they're not open to your own interpretation. If Canon says that 1:2 means that the difference between A and B is one stop, then that's exactly what it means. So, if you want your main light to be one stop more than your fill light and your main is the slave, then what you need to do is set the flash ratio to 1:2. Period.

Now, if you don't like the result you got with the setting, then, of course, you can change the setting until what you get is exactly what you want.

Excerpt from page 40 of the 580EX manual:

HOSTED PHOTO
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Hi Dave,

I don't understand why you keep using the expression 'almost one stop'. That's like saying f/8 is almost one stop smaller than f/5.6. It IS one stop smaller.

PacAce wrote in post #2698202
This really has nothing to do with whether Canon got it right or not. It's all about what the markings on the flash is supposed to mean and they're not open to your own interpretation. If Canon says that 1:2 means that the difference between A and B is one stop, then that's exactly what it means. So, if you want your main light to be one stop more than your fill light and your main is the slave, then what you need to do is set the flash ratio to 1:2. Period.

Now, if you don't like the result you got with the setting, then, of course, you can change the setting until what you get is exactly what you want.

Excerpt from page 40 of the 580EX manual:

Hosted photo: posted by PacAce in
./showthread.php?p=269​8202&i=i167725910
forum: Flash and Studio Lighting

I'm not sure where you've read that Canon says that 1:2 means one stop difference. Ratios are NOT stops. Ratios are a combination of how much light strikes different parts of the subject's face.

This is how ratios are calculated for a 2:1 lighting ratio. You take a subject and pretend that subject is in the centre of a circle. At a distance away from the subject (say two meters) you set up a studio flash on full manual. That flash is 45 degrees to one side of the subject and this is the Main light. Now you set up another identical flash at the same power and the same distance. But this time its right in front of the subject and within 20 degrees of the camera.

The Main light from its 45 degree angle is hitting one side of the subject's face. The fill light - with the same power - is hitting BOTH sides of the subject's face. So ONE unit of light has hit the shadow side of the face, while TWO units have hit the highlight side of the face. THIS is a 2:1 lighting ratio, and BOTH flashes are set to EXACTLY the same output. If you measured either you'd get (say) f8, but there is MORE light on the highlight side.

That's the reason that the fill MUST be within 20 degrees of the camera, and that's to insure that its output stikes both sides of the subject's face.

I can take you through 3:1 lighting if you'd like but that involves some inverse square arithmatic.

When I took a portrait lighting course the instuctor worked through this with us but then he said "Just remember that for a 3:1 lighting ratio there's almost, but not quite, one stop between Main and Fill." Since I use stops all day this made sense. Figuring ratios with math and on the fly does not.

TMR Design wrote in post #2698521
Hi Dave,

I don't understand why you keep using the expression 'almost one stop'. That's like saying f/8 is almost one stop smaller than f/5.6. It IS one stop smaller.

My flash meter is sensitive in 10% increments of a stop. If I measure a flash the read out might say f8.2., which I would read to mean f8 + 20% of another stop. If the Main is sept to f11.0 then f8.2 - the Fill light - is "almost but not quite" one stop less than the Main. And that's a 3:1 lighting ratio.

DaveG wrote in post #2702178
I'm not sure where you've read that Canon says that 1:2 means one stop difference. Ratios are NOT stops. Ratios are a combination of how much light strikes different parts of the subject's face.

This is how ratios are calculated for a 2:1 lighting ratio. You take a subject and pretend that subject is in the centre of a circle. At a distance away from the subject (say two meters) you set up a studio flash on full manual. That flash is 45 degrees to one side of the subject and this is the Main light. Now you set up another identical flash at the same power and the same distance. But this time its right in front of the subject and within 20 degrees of the camera.

The Main light from its 45 degree angle is hitting one side of the subject's face. The fill light - with the same power - is hitting BOTH sides of the subject's face. So ONE unit of light has hit the shadow side of the face, while TWO units have hit the highlight side of the face. THIS is a 2:1 lighting ratio, and BOTH flashes are set to EXACTLY the same output. If you measured either you'd get (say) f8, but there is MORE light on the highlight side.

That's the reason that the fill MUST be within 20 degrees of the camera, and that's to insure that its output stikes both sides of the subject's face.

I can take you through 3:1 lighting if you'd like but that involves some inverse square arithmatic.

When I took a portrait lighting course the instuctor worked through this with us but then he said "Just remember that for a 3:1 lighting ratio there's almost, but not quite, one stop between Main and Fill." Since I use stops all day this made sense. Figuring ratios with math and on the fly does not.

Dave, I'm pretty sure that you know what you are talking about and I am not questioning or debating your points. But they have nothing to do with the OP's original post and what the ratio markings mean on the EX flash.