A very simple technique in outdoor fashion photography which uses on location flash lighting. This look was made popular in the early 90's and required generators with powerpacks, which in turn got down to batterypacks today. All leading studio light manufacturers have portable batterypacks. Some enthusiasts use off camera flashes which is good for crosslighting or balancing sunlight....but for against sun the power isn't quite upto it.
You need a lot of power to shoot against sun. Let me rephrase, you need a lot of power just to shoot against setting sun. In terms of wattage...atleast 500watts/sec light. And if you plan to shoot against afternoon sun, atleast 1000w/sec. Some pros shoot with 3000w/s of power from a single light source at noon, to make the sun look like a star. That is pushing it a bit too much. But if you are thinking that why you need 500w/s for late afternoon sun.......well, the answer is simple. You need power to be in control....especially in natural settings....and even more if it's a paid assignment.
What kind of control? Ok, first of all, never compromise in lighting a subject. Like in a studio, you know that a diffuser gives soft light. But using a softbox or any diffuser sucks up a lot of light. So, do you shoot your subject with hard light from the flash? If not, why should shooting outdoors be different. The model needs the same diffused light to give softer shadows even outdoors. With more power, you have the ability to place the light far from the model and with layers of diffusers. For a photographer, THAT is control over lighting situation.
The Star Effect
You might have seen this star effect quite often in magazines. Lets see how its done. First lets take a quick look at the lighting of the above images. Yes, very simple as you can see. We used a 32deg honeycomb grid and covered it with a gateway/diffusing paper on a 500w/s monoblock(powered with a portable generator) to give a kind of a soft radial spot on the upper body. We intentionally made the lower half darker because text matter in white was coming on that part according to the layout.
Anyway, the theory to the star effect is that it will be visible when the light source(any, but in our case...the sun) is revealed through a tiny opening or a gap. In the case above, i positioned the camera so that the sun could be just seen from the curve of the models palm. Also, to capture it, you have to shoot at apertures like f16 and above. If the same picture was shot at f5.6, the small star would be a big glow of light instead. So, the way to do this is to set the aperture at f16(atleast) and adjust the shutter speed to get the desired look of the background. Ideally this would be 1/250 or lower, depending on the setting sun. Now bring in the flash,and boost the power so it meters for this same setting...and shoot as fast as possible until the sun sets!