I think there is still some confusion over terminology, and the difference between wrap and bleaching (edge degradation).
Wrap is about the width of the background, relative to the subject, and how much of it reflects off the subject. Wide background, subject close to it, equals lots of wrap. And the opposite of course.
Bleaching is down to nothing but the difference between the background exposure and the foreground (main subject light). It has
nothing to do with the distance between the subject and the background. This distance can be used to control wrap (as described above) but not bleaching. If you maintain the exposure level between the background and foreground lights, bleaching will be the same. Moving the subject forward reduces the intensity of the background light (inverse square law) but if you turn it up to compensate and maintain the correct front/rear ratio, you will get exactly the same amount of bleaching (but reduced wrap). (I think there is some confusion here due to the difficulty of taking incident light readings when you have effectively two different light sources. Incident readings should really be taken from the subject position, but that doesn't work so well in this case. The LCD with blinkies enabled and a careful look at the histogram should be the deciding factor.)
Flare is something different again. It's a lens fault, and some are better than others. Flare comes in two flavours - coloured spots and patches which are obvious, and veiling glare which often goes unnoticed. Veiling glare is a general reduction in overall contrast, loss of 'punch' and 'pop' which flattens the image and makes it look very dull. With so much bright light blasting at the lens it is impossible to eliminate flare completely, but covering over any unnecessary areas of bright background will help a lot, as will screening off those areas.
A lens hood too will make a big difference, especially if you cannot do any of the other things. Lens hoods on zooms are pretty useless, and only optimum at the wide end. Lenses designed for full frame when used on crop cameras are also way off optimum. As I mentioned above, the hood I use with my 17-55 lens on a 40D is 4in long and from my 100-400L lens - at 50mm it is perfect. You can make a very good lens hood with two L shapes of black card and some BluTac. Stick it to the front of your normal lens hood and keep moving the L shapes inwards until you get vignetting, then move them out a bit. You will be amazed at how much extra shading you'll get. Try some test shots with and without to see the difference. Or just get one of these very good adjustable bellows hoods from Lee
http://www.warehouseexpress.com/buy-lee-single-slotted-lens-hood/p1010399 £89 well spent for any studio photographer
Final thing is spill, which can look like flare - basically just light from the background (and other lights) spilling around the room and bouncing/reflecting off ceilings and walls, carpets and furnishings. In the average domesting setting, there is tons of this stuff and while it's not so bad as flare it will soften the effect of the front key light, sometimes a lot. You won't get any dark shadows at all. Kill it by covering over any unnecessary areas of background, and don't use a shoot-through brolly which are hopeless for spill as half the light comes straight out of the back. Normal brolly or softbox are much better.
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But like I say a few secs in Ps should help.
