Someone Please Explain Fill flash

C.Fn 3 set to Auto [on the 30D] allows the camera to sync with any speed that is needed, called for by the ambient lighting it sees. In other words, if the flash were not on the camera and you use Av Mode and with whatever ISO and aperture you have set, it comes up with a shutter speed of 1/400sec, then that's what it shoots at, 1/400sec. Now put the flash on and set the camera custom function 3 to Auto, set the flash unit to HSS, and in the same light as before, you still get 1/400sec shutter speed but you can shoot at that speed, the flash will fire a burst that will light the image without blowing it out. Whereas, if you set custom function 3 to 1/250 fixed, it's going to shoot at 1/250sec and the image will probably be dark.

I set ETTL II to Evaluative.

Franko515 wrote in post #3249502
so whats the good of C.Fn ?

Custom function 3 has no real value in my book. It just makes your Canon act like a Nikon, as I mentioned in post #8.

Leave C.Fn. 14 at 0 (Evaluative) for fill flash. It will evaluate the pre-flash, "find" your subject, and automatically compensate for the ambient light.

I get more consistent results with C.fn. 14-1 (average) indoors with flash as the main light. But be sure to switch it back to 0 when you go outdoors!

canonloader wrote in post #3249565
C.Fn 3 set to Auto [on the 30D] allows the camera to sync with any speed that is needed, called for by the ambient lighting it sees. In other words, if the flash were not on the camera and you use Av Mode and with whatever ISO and aperture you have set, it comes up with a shutter speed of 1/400sec, then that's what it shoots at, 1/400sec. Now put the flash on and set the camera custom function 3 to Auto, set the flash unit to HSS, and in the same light as before, you still get 1/400sec shutter speed but you can shoot at that speed, the flash will fire a burst that will light the image without blowing it out. Whereas, if you set custom function 3 to 1/250 fixed, it's going to shoot at 1/250sec and the image will probably be dark.

I set ETTL II to Evaluative.

Curtis N wrote in post #3249594
Custom function 3 has no real value in my book. It just makes your Canon act like a Nikon, as I mentioned in post #8.Leave C.Fn. 14 at 0 (Evaluative) for fill flash. It will evaluate the pre-flash, "find" your subject, and automatically compensate for the ambient light.

I get more consistent results with C.fn. 14-1 (average) indoors with flash as the main light. But be sure to switch it back to 0 when you go outdoors!

Ok got it, i think. I will do test today and see what I come up with.

Also setting the camera to manual, w/flash (set to ettl) to expose for a sky (to make it blue) I would just expose for the sky (since i can now get over 1/250 w/HSS) and the flash should light the subject properly (person in front of city skyline), but if not i can add or subtract FEC (flash exposure compensation). HSS is for Av, Tv and M modes. Is this correct?

Last thing, I hear people say they had flash at full or half power is that because of FEC or is there a way to just set it at half or 1/3 power

I hope you guys dont grow tierd of my dumbness (is that a word?) I really do thank you guys for your replies. I try to read up on flash but end up getting confused, there is so much info and mis-info to wade through.

Again THANKS

Right.

I have the 550ex and you can set the power from 1/1 to 1/128, although I just use the wheel on the camera to use FEC.

canonloader wrote in post #3249790
Right.

I have the 550ex and you can set the power from 1/1 to 1/128, although I just use the wheel on the camera to use FEC.

Thanks, I am armed and ready

Since I understand a little better THIS post by Curtis makes perfect sense now. I had the HSS figured all wrong, somehow I let myself think this was C.Fn 3 (yes I know im dumb)

Don't call yourself dumb. This stuff confuses a lot of people.

Think of it this way: Outdoors you have two options to properly expose for bright sunlight. You can use a moderate shutter speed (1/250 or slower) along with a relatively small aperture.

Or you can use a fast shutter and a wider aperture. Whether you're using Av, Tv or M, you still need a relatively fast shutter, or a relatively small aperture, or some combination thereof.

So you need to make a choice. You can set the shutter at 1/250 and then stop down the aperture for proper exposure. In bright sun this will require a relatively small aperture that will give you a lot of DOF and keep the background relatively sharp.

But maybe you want a wide aperture to blur the background. In this case you will need a fast shutter speed which requires HSS. But HSS uses the flash less efficiently, reduces the range and generates longer recycle times and less battery life.

Those are your choices. Now you need to decide what's important to you and use the appropriate strategy.

Now I have another question. What does the camera metering settings play in all this? Center Weighted Average, Spot, Partial and Evaluative all meter deifferently and can give different results.

canonloader wrote in post #3251373
Now I have another question. What does the camera metering settings play in all this? Center Weighted Average, Spot, Partial and Evaluative all meter deifferently and can give different results.

These two articles may be what your looking for

http://www.planetneil.​com/faq/flash-5.html

http://www.planetneil.​com/faq/flash-compensation.html

Hope this helps you out as much as you guys have helped me

this is making my brain hurt. I want to understand it, but alas, my poor noggin can scarcely handle it, and my models are no longer willing to go into the sun with me. Boo hoo

It's really simple. Going back to the original question and nothing more, which was how to get fill flash to work. Fill flash being to light the shaded side of the subject when the subject is backlit.

Set the C.Fn 3 to Auto, set C.Fn 14 to Evaluative, set the camera to Av mode, set the flash unit to ETTL II then use the camera as if there was no flash unit on it. The camera will meter the ambient light and give the same shutter speed it would if the flash were left at home. Push the button and what happens is, the flash unit pulses just enough light to light the shaded side of the subject and not blow out the rest. Simple.

If you want to use the flash to light the subject in the dark, then use other settings, thats not fill flash.

Thanks Mitch, giving that a try!

You'll get it.

What I was trying to do was to shoot a bird that was between me and the sun. Of course, the side towards me would always be dark. Trying to fix that kind of mess in Photoshop just adds noise and I wanted to avoid that. So using fill flash correctly will light the side of the bird towards me without blowing out any leaves or other items in the picture with a full pulse of light. When you do it right, it looks completely natural.

Just as a side note, I am really sorry I hijacked your thread, I apologize that was not my intent. I was so wrapped up in understanding flash I just jumped in, and I shouldnt have. Again I am sorry.

Naaa, you didn't. This is what it's all about here.

canonloader wrote in post #3255763
It's really simple. Going back to the original question and nothing more, which was how to get fill flash to work. Fill flash being to light the shaded side of the subject when the subject is backlit.

Set the C.Fn 3 to Auto, set C.Fn 14 to Evaluative, set the camera to Av mode, set the flash unit to ETTL II then use the camera as if there was no flash unit on it. The camera will meter the ambient light and give the same shutter speed it would if the flash were left at home. Push the button and what happens is, the flash unit pulses just enough light to light the shaded side of the subject and not blow out the rest. Simple.

If you want to use the flash to light the subject in the dark, then use other settings, thats not fill flash.

Could this also be used indoors when using the dragging shutter technique?