Gordon - I've used this size for a few years now and I find it the key modifier I turn to when I can't use a static set-up. I didn't use the lastolite version - I bought a cheaper flea bay bobbie - so there could be some difference due to diffusion materials being used and number of diffusion layers.
Mine was a single diffusion layer on the front. I opted for this to retain some power when working outdoors. This size of soft box suits a single flashgun well because you get an even light source and you also get the benefits of the an increase in apparent light size when compared to bare flash.
I use mine for some full body stuff, but mainly half-body shots where it excels because it just modifies the light enough to get that soft light associated with soft boxes and an attractive drop-off of the light. Placed close I really like the quality of the light and even when set further back for full body, despite the loss of power over a bare flash, there is a noticeable modification of the light.
The size means it's easily hand-held; I just grabbed the speeding and used a wireless trigger system to allow me to move it around the subject while holding the camera in the other hand.
T be fair, my £30 box lasted pretty well (two years, used virtually every day in all conditions) but I'm on the lookout for another because mine is now totally knackered. I doubt a Lastolite one would have lasted any longer TBH.
These were shot with one (click through to see the lighting info):
Duncan (lighting test) by
Pat MacInnes, on Flickr
My Partner In Crime.... (Explored) by
Pat MacInnes, on Flickr
Rob's Big Chub by
Pat MacInnes, on Flickr
One tip for these soft boxes that trap the speeding in position is to fix on some velcro loops that can be fixed around the speeding to keep it attached.
At the end of the day, it's about light source size relative to the subject. As a portable, handheld solution I'd go with a 40cm soft box but as a portable soft box to go on a stand, then I reckon 60cm may offer better quality of light. I also use a 28" Westcott Apollo, which is excellent, but it requires setup time and is something I really only use when I have the time, and mores when I'm shooting indoors.
Hope this all helps
