Diffusion... right scenario?

I've yet to take portraits with flash, but am hoping to do so very soon...

I have a 580ex II which would be mounted to top of camera. Thinking it will be a mix of direct sunlight, as well as "broken sunlight with shadows" through trees...

Is this where a diffuser on the flash would be a good idea? What about everyone who says these diffusers are utterly useless and just cause you to have to unnecessarily increase flash power?

Kaitlyn, the issue is that only SIZE (not the mere presence of) a diffuser is the key aspect that determines its effectiveness, when it is used as a direct source of light.

When a flash is pointed up to the ceiling, the ceiling becomes a 'large virtual source of light' and that provides the soft lighting with fewer shadows. Putting the 'diffuser' on the flash head does nothing to make the light from the ceiling 'softer' because it is no larger than the flash head itself. An Omnibounce pointed upward does send some light straight forward to the subject (a benefit, as a 'second source' sending direct light forward in addition to the ceiling bounce), filling in the eye sockets and under the chin -- with light that is virtually AS HARSH AS pointing the flash straight ahead -- as well as sending light up to the ceiling. But it also sends light backward and to the sides, wasting light except in small rooms.

1000arms wrote in post #12486635
You might want to read https://photography-on-the.net …php?p=1585420#p​ost1585420 from https://photography-on-the.net/forum/showthre​ad.php?t=138907 .

And then look at these: One shot has flash fill. Notice the detail in the black coat & white boa.
Angeline outdoors

Here is proof of how a small 'diffuser' in pointless when there is nothing to bounce light off, to soften the light

https://photography-on-the.net …p?p=12396412&po​stcount=61


And here is what happens of the modifier increases the apparent size of the the flash head (in this case, increasing size from about 3 sq.in. to 35 sq.in.), when fired forward directly
https://photography-on-the.net …p?p=12403237&po​stcount=78

Hi Kaitlyn,
Given that you have a 7D, you can fire the 580EX wirelessly using the pop-up flash on the camera. This usually gives more pleasing lighting than on-camera flash. Regarding diffusion, something like the Lumiquest Softbox III (72 sq. inches) can be very useful if it is placed fairly close to the subject (eg. 2-4 feet). Next step up from that would be something like the Cheetah Qbox 16 or 24. Off-camera flash using any of these will require either an assistant to hold the light or an inexpensive (about $25) light stand. As stated above by others, very small diffusers and dome diffusers are essentially worthless outside with no bouncing surfaces available.

HughR wrote in post #12489308
Hi Kaitlyn,
Given that you have a 7D, you can fire the 580EX wirelessly using the pop-up flash on the camera. This usually gives more pleasing lighting than on-camera flash.

Kinda forgot about that feature, but I actually have wireless triggers (before I got 7D...). still would need a stand or another hand to hold it off camera though