Finally took my 580EX outside experimenting with Fill Flash

i didnt think he was maxing it out. he says he used +1/3 FEC. am i missing something? i will most likely upgrade to the bigger flash unit soon anyways but im curious as to why you say he was maxed out. im just always willing to learn new stuff, more so when it involves flash.

Wilt wrote in post #2384881
Obvious only to those who know the 580EX was maxed out. It takes an understanding of Guide Numbers to realize that fact, and with increasing dependence on ETTL tens of thousands have no clue what Guide Number is and how it can be useful!

Well Wilt I must admit that is one of the next things I want to delve into and learn. I keep seeing and reading about guide numbers but knew that I could get the ball rolling without understanding what they were or meant. Now I want to thoroughly understand how to interpret and use guide numbers.

I'm going to go read this now:
Flash Photography 101: Chapter 4 – Guide Numbers and High Speed Sync

EDIT: I did neglect to indicate the flash Zoom setting was on 105mm.

jjmucker wrote in post #2384918
i didnt think he was maxing it out. he says he used +1/3 FEC. am i missing something? i will most likely upgrade to the bigger flash unit soon anyways but im curious as to why you say he was maxed out. im just always willing to learn new stuff, more so when it involves flash.

Ok, here's Robert's statement: "I was about 20 feet away in both shots using my 85mm f/1.8 lens. I find that I hardly ever shoot in Av mode and have really taken a liking to shooting in Manual mode. I like the control it gives me. For those shots I was at 1/250s (max sync speed with flash), F/11, ISO 400, no EC, +1/3 FEC. Using these settings I was able to just focus and shoot without having to make changes and I let the flash do its work."

20' * f/11 = GN220.

I neglected to notice his comment about ISO400! The 580EX has an official ISO100 guide number of 190 when the head is zoomed to 105mm coverage. The ISO400 Guide Number would be 380, easy to derive from ISO 100 GN=190 *2. So at f/11 with ISO400, the 580EX could reach out as far as 35'. His flash was not maxed out after all, because he was using ISO400. But it would have been maxed out with ISO100.

As far as his comment about FEC +1/3, he could have dialed that into the control, but the flash could still have fallen short of attaining that level of output (such as if he were using SIO100)!

np, thanks for clearing it up.
you can really see the difference between the 430ex and the 550ex when its explained like that.

That sure does make sense and now I'm going to apply that basic formula to other situations with flash to gain a better understanding and to know when there simply is not enough flash power.

I do have a question.......
If I were to have another flash (keep it simple and say another 580EX), how do guide numbers and flash power work when using multiple flashes?

TMR Design wrote in post #2385007
I do have a question.......
If I were to have another flash (keep it simple and say another 580EX), how do guide numbers and flash power work when using multiple flashes?

Light is like water, it is additive. Two hoses output twice as much total water as one hose alone. Two flashes of the same model will output twice as much light as one flash alone (adding +1EV of light to the scene)

Wilt wrote in post #2385023
Light is like water, it is additive. Two hoses output twice as much total water as one hose alone. Two flashes of the same model will output twice as much light as one flash alone (adding +1EV of light to the scene)

I should have known that. You've told me that before. Thanks.

BUT.... does it give you twice as much range? Or twice as much light over the same distance?

TMR Design wrote in post #2385081
I should have known that. You've told me that before. Thanks.

BUT.... does it give you twice as much range? Or twice as much light over the same distance?

Twice as much light means the effective GN goes up by 1.4x. So 1.4GN / aperture = distance. Distance goes up because there is more light remaining after the inverse square falloff of intensity.

Wilt wrote in post #2385275
Twice as much light means the effective GN goes up by 1.4x. So 1.4GN / aperture = distance. Distance goes up because there is more light remaining after the inverse square falloff of intensity.

As always, thank you. It'll take some time to get this under my belt but I'm beginning to understand.

TMR Design wrote in post #2384532
There isn't much that I could bounce the flash off so I brought my white bounce card and gave it a try.

Fill flash can be a tremendous benefit outdoors. I will only add one caveat to this thread: With the apertures typical of daylight shooting and 1/250 shutter speed, use of a bounce card or any other flash modifier will significantly reduce your range.

Softening the light from the flash is generally unnecessary when it's used as fill. Outdoors, direct flash is usually the best (and easiest) choice.

Curtis N wrote in post #2385433
Fill flash can be a tremendous benefit outdoors. I will only add one caveat to this thread: With the apertures typical of daylight shooting and 1/250 shutter speed, use of a bounce card or any other flash modifier will significantly reduce your range.

Softening the light from the flash is generally unnecessary when it's used as fill. Outdoors, direct flash is usually the best (and easiest) choice.

Thank you Curtis. I had tried some direct flash but it looked a litle stark and unnatural. In that case should I have just dialed down some FEC?

TMR Design wrote in post #2385444
I had tried some direct flash but it looked a litle stark and unnatural. In that case should I have just dialed down some FEC?

Perhaps. Another thing that can make outdoor fill look "unnatural" is a difference in the color temperature of the flash vs. ambient.

Curtis N wrote in post #2385454
Perhaps. Another thing that can make outdoor fill look "unnatural" is a difference in the color temperature of the flash vs. ambient.

I should have been more clear. When I say it looked stark it was bright and appeared overlit, almost like when you are indoors and use direct flash and the subject(s) have a bright appearance in their face.

I find I'm always adjusting FEC to match conditions when using outdoor fill. I usually wind up somewhere between -2/3 and 0.

And it can create shadows if the background is close. The more fill you use, the more noticeable the shadows.

Wilt wrote in post #2384784
Just some observations for the benefit of those who are motivated by Robert's photos to try flash fill...

Robert used a 580EX to provide fill at f/11 to subjects 20' away...he was MAX'd out in the power output from that flash! If you use a lesser flash, you will not be able to use fill flash to the same distances. And if you think you can open up the lens to make it easier on the flash, remember that he was at 1/250...so going to higher shutter speed for proper exposure with larger aperture would force the use of HSS, but that causes the flash's light output to drop very precipitously!

So set your expectations accordingly, with lesser output flash units!

I wonder if I’m mistaken as I’m also new but hopefully learning from the wealth of knowledge that is shared in this forum.

It’s may understanding/recollec​tion that the 580 essentially has a 1 stop advantage over the 430? If this is correct wouldn’t we simply be able to lower the shutter speed to 125sec and achieve the same results? Would we also not be able to increase FEC levels to further add additional flash if required? No doubt that the 580 will out power the 430 but in regards to this particular shot it seems to me that it would have been sufficient.

Anyway great shots I’m sure your glad you had your flash on you. I just recently got my 580 last week and haven’t had the opportunity to try fill flash outdoors yet but I have a feeling it’s going to see some action soon