Well I'll be the odd man out here, I think it looks phony for a couple reasons. First, your color temperature. The cool color of the studio lights clashes with the warm sunset. If you're shooting someone by sunset light, the strobe color should be gelled warm (as though it was reflecting the sun, not a cool strobe). Second, for a natural look, I prefer a one-source or unidentifiable light source on the front of the model - unless you're going for something specific or dramatic. If you want a hair light (which could look natural) it certainly has to be warm to convey the effect that it is the sun in her hair. So... if you're going to do it in studio and drop in a background, you have to light it with the background shot in mind, and ask yourself, "where would the light go?". The trick is to balance the light intensity with the background to make it look natural - we subconciously expect the background to be brighter than the foreground simply because that's what we're used to seeing.
In this old sample below, we shot the model and boat mockup in studio against a gray background and the client dropped in the sunset behind. Notice how there is only one main light on her body and yellow light on her hair coming from the direction of the sun in the background (The yellow on her legs was a little artistic license, because they were supposed to use a shot with the sun more in the center of the shot).<br>
Now here is another shot which I think looks like it could be in studio or "live". It was shot live, with one strobe (bastard amber gel over it to warm it up), but I dug this one up because it does look like it could be a green screen shot. I think its borderline either way.<br>
Here's one I did more recently, and also "live" (I don't have any recent examples with dropped in backgrounds). In this shot notice how the sunset is providing the halo around the model's hair. That comes from using a slow enough shutter to let the light bleed (as opposed to the calendar cover above), which of course adds to the realism makes her look like she's actually in the shot, which of course she is:<br>
Now... I would love to read about how the green screen process works if you could share that. I'd love to play with it.<br>
Andy Pearlman Studio