The power loss using high speed sync modes is huge which is why he has the flash so close in, exactly the same could be had with keeping to the sync speed and stopping down or using an ND filter. There is no free lunch.
How would one of you guys go about taking shots like those?
Cheers
They're not quite 'blocking out the sun'. They're adding a differential - or even in the case of the guy in the deckchair - barely just matching the sun. You could do that quite easily with a 200ws or 400ws battery portable or even a Sunpak 622. They look pretty much like flash on camera or on a bracket and at quite close distances. The format suggests they might even be MF with a flash bracket.
A standard parabolic reflector would work better than the Sunpak focused reflector, and at those distances even a 19" softbox would work - with or without cover.
Your camera has a range of about 7 stops, which means if you started with a normal Sunny 16 exposure of the background in the beach you'd need to underexpose the background by about 6-7 stops to render the white sunlit sand dark gray. Reducing by 2-3 stops will render the white sand med. gray. You can test / visualize this by going outside with the camera, putting white, gray and black content in the sun, start with a normal exposure and bracket and add ND until you make the white objects as dark as you want the sand.
Where you wind up with the camera aperture + ND will give you an idea of what GN you'll need for the flash in the foreground. For a wide full length shot 1200W/S - 2400W/S is probably what you'll need to turn noon into midnight in moonlight. Since you are blocking out all the ambient light on the foreground and with it the modeling the natural lighting creates you'll want to plan your lighting strategy more or less how you'd light the subjects indoors with centered fill to lift the shadows on the front side, off-axis key lighting, and perhaps a flash behind as rim lighting, depending on where the direct sun is relative to the subjects and how much of the natural light you kill. If you use centered fill to lift the shadows in the foreground you'll need less power on the key light to expose the highlights because the fill will lift them half way. So where you might need a 2400W/S flash with a one light "fill" strategy you probably can get by with two 1200 W/S in a key over fill strategy.
I never try something I've never done before without testing first. The best way to answer your question and plan a viable strategy would be to rent one or two 1200 W/S flashes for a day, take them out into the sun and shoot some tests. That way you can nail down the power needed for the distances you plan to shoot from, take measurements and notes so on the day of the shoot you can rent the same equipment and set up per your notes without a lot of trial and error.
