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

PacAce wrote in post #2702273
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.

Well he asked for a one stop difference. "I'm hoping to achieve f8 with the 430 and around f5.6 with the 580." I said select 3:1 (which in the Canon Wireless world is 1:3).

You said "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."

I disagreed, explained why, and I think that I was still on point.

DaveG wrote in post #2702385
Well he asked for a one stop difference. "I'm hoping to achieve f8 with the 430 and around f5.6 with the 580." I said select 3:1 (which in the Canon Wireless world is 1:3).

You said "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."

I disagreed, explained why, and I think that I was still on point.

Dave, please go back and take a look my previous post where I attached an excerpt from the 580EX manual (page 40) and carefully read what is written there. It'll become pretty obvious from reading it that you are wrong and I am right.

PacAce wrote in post #2703471
Dave, please go back and take a look my previous post where I attached an excerpt from the 580EX manual (page 40) and carefully read what is written there. It'll become pretty obvious from reading it that you are wrong and I am right.

I've looked at that manual extract and I want you to explain something to me. If you have the flashes set up at 1:1 and one is at 45 degrees (the main) and the other is at the camera position, and they both output EXACTLY the same, how does the same amount of light fall on the shadow side of the subject's face as on the highlight side? Is there not twice as much light hitting the highlight side?

In reality the only way that you'd ever get 1:1 is if you split the two flashes so that they both are at 45 degree angles so neither can see the other side of the subject's face.

Now if I actually did place the two stobes in the classic portrait position and had them output at exactly the same power from the same distance then that ratio would not be 1:1 but 1:2. Once again if you measured each flash at the subject position they would be exactly the same. Both would read out f8 but I still get a lighting ratio.

Try that with some manual flashes and don't believe me, just measure them. One flash at f8 at the subject position and the other at f8 at a 45 degree angle to the subject. Now measure them together. IT WILL NOT BE ONE MORE STOP OF LIGHT. The combined exposure will not be f11, it will be f8 and roughly a half. So if 2:1 is NOT a full stop as I maintain, and you can chack for yourself, what is 3:1?

I stand by my previous posts, and I just think that Canon got it wrong. Now am I smarter than Canon? No I don't think so. But I may well be smarter than the guy who wrote that page of the book.

Dave, I think you're missing the whole point here and obsessing on your 3:1 ratio too much. Yes, from the camera's perspective, two lights that are one stop apart will give you a 3:1 ratio as you said, assuming you are talking about the overall lighting to fill lighting, which is one way of denoting ratios. But it's not the only way. Ratios can also be denoted in terms of the relative light intensity of one light over the other light, which is how the Speedlites are set up and more specifically as the Group A light over the Group B light rather than main light over the fill light.

If you have a Sekonic light meter, it also denotes ratios the same way Canon does, one light relative to the other. Not the total light relative to the weaker one when you measure light intensity ratios (although, if you want to, you can also measure the total light against the fill which will give you the ratio you are talking about).

And here are a few other source that do the same (i.e. measure one light relative to the other):

http://www.vividlight.​com/articles/1916.htm
http://www.studiolight​ing.net …for-portrait-photography/

You can also find similar references in book on lighting as well. Christopher Grey's "Master Lighting Guide" is one that comes to mind off the top of my head.

Long story short, Dave, you're talking oranges when I'm talking apples.