Strobist Talks all about outdoor and indoor studio type shots using small speedlights.
That has been linked so many times here, that I would think a search would give you at least like 50-100 hits... lol
Now the thing is we can talk all sorts of extremes all day. If your idea of a studio type shot is outside against the sunset lighting up a model using a large umbrella for extremely smooth light, then no the speedlight won't do.
Not to contradict my good friend Garbz, but sunset shots are where speedlights shine. As long as we are not talking bright daylight conditions, I can overpower the sun pretty easily and not use full power on my flash. Please let me demonstrate:
Nothing special, just a pretty bright day (not noon, it was around 4:30 in the afternoon and there was a good partial cloud doing some nice diffusion), but F/8 at 1/80th and off camera flash for lighting the subjects shows that they kinda "stand out" brighter than the ambient. This was done with a single SB-800 at 1/2 power.
Current conditions will dictate if that speedlight will do it or not, but if the sun was even 2 stops higher, I could not get this shot with a speedlight and would need 2 speedlights or a studio head to get the same shot. If shooting under the "Sunny 16" rule of conditions... speedlights are sorely pressed to do a good job.
For those that are not sure what I mean, the sunny 16 rule is just an old rule from the film days meaning that, on a bright cloudless day, if you set up your camera to F/16 and 1/125th shutter speed, these settings would net you a proper exposure.
But for much else, modern cameras don't really need to nuke their subjects. If you're not fighting against the sun then upping the ISO reduces the power required and then yes 2 SB-600s would be more than enough to light a model in a wide variety of circumstances.
For sure!

I would have to say that this scenario could easily cover 80, maybe 90% of all possibilities. This is why I advocate speedlights for the most part. Sure they do not do it all... I did a wedding where my settings were F/16 for deep DOF and I needed to set shutter speed to 1/2500th to cut down ambient. I then overpowered the ambient using a single studio head at 1/2 power and the results were fantastic!
From an e-session that I did a couple days ago taken by my mentor (used with permission):
The setup was a single flash at 1/2 power shooting through an umbrella at camera left (very close to camera, about 4 feet away) and a bare speedlight set to rim-light from behind the subjects at 1/16th. Obviously at sunset.
