Problem is, as excellent and (so far) reliable as the ancient Bowens are, they are big and bulky units which cannot be used on location. I already have 2 Nikon SB-800 Speedlites and theses offer considerable advantages:
- Compact and light
- Battery power means location use (I also have SD-8a battery packs for quicker recycling)
- Works with Nikon Creative Light System (CLS) so exposure and power of each light can be controlled wirelessly from my D7000
Of course they are not as powerful as the Bowens, but it's incredibly difficult to judge from specs alone, and there is no real comparison I could find on the web. Trouble is, studio flash power tends to be quoted in watts, but this is really a measure of the electrical energy delivered to the tube, not the light output, which will vary depending on the efficiency of the tube and reflector. The Bowens are apparently 250W, according to this.
So I did a 'real world' test for myself, I fired the Bowens through a Westcott 43"/110cm white umbrella at my Sekonic flashmeter approximately 2 metres away, and then the same with the SB-800. I also attached the Nikon diffuser to the SB-800, as, although this reduces the output a little, it spreads the light nicely over the brolly (the flash covers 104 degrees, equivalent to a 14mm lens when the diffuser is attached). This enables the Speedlite to give a similar quality of light as the Bowens in this setup. Both flashes were set to full power.
As expected the Bowens beat the Speedlite by some margin, showing f/11, 2 stops more powerful than the Speedlite at f/5.6. So, still usable for individual portraits, especially as in practice the light could be positioned a lot closer to the subject. Of course using a second SB-800 firing through the same brolly would narrow this gap down to about 1 stop, but I'd probably need a third SB-800 to act as a fill light.
Why the SB-800, why not a more modern unit? Well, hardly used one's can be picked up easily for around £200-£220, which is about £120 less than a SB-900 or SB-910. Although it has a clunky interface compared to the more modern units, it is still the joint most powerful unit tested at speedlights.net and you can also pick up matching SD-8a battery packs for around £60.
Word of caution: if you're thinking of using some old studio lights with your modern DSLR, check carefully that the trigger voltage is not going to fry your camera. Or, do what I do and use a radio trigger so there is no electrical connection at all between flash and camera.