super white background with 600W compact flash?

[Deleted member 11105]

Hi, i am looking into getting the Elinchrom style RX 600w package of two heads and then also a white vinyl backdrop. but before i decide it would be useful to get some advice. if i only have one head for the subject (+ reflectors) and one head for the background, will this one head be enough to light the background and make it superwhite. i guess the shot i really want to take would be an upper body shot, so would that be a small enough area to light evenly? i would also be interested to know if you think it could light the background for a full body shot. in a book on lighting i have they allways have two heads on the background (it doesn't say what wattage), so that has made me wonder?

thanks

 

[Garry Edwards]

To a large extent, knowledge, skill and care can make up for lack of equipment so yes, you can achieve reasonably even lighting with a single light. Ideally you should use a background reflector (expensive) but an ordinary wideangle reflector will produce reasonable results as long as it hits the background square on, which means that it will need to be hidden behind the subject.
The light won't be even (it will fall off towards the edges) so you'll need to overexpose more than would be necessary with two or four lights on the background, and because of this you'll need more space between subject and background, so that the reflected light has lost most of its power before it hits the rear of the subject - otherwise you'll have the fine detail like hair degraded, a fault you see in a lot of beginner studio shots.

If you're planning on getting 600J heads (not watts, which are a measurement of power consumption for continuous lights) I wonder why you think you need that much power. You'll struggle to reduce the power enough in most situations. 300J is more than enough for the average portrait studio. I'm not knocking the Elinchrom Style, they're a much better product than their D-Lite series, but I do question whether you need that much power.

 

[Garry Edwards]

Well, if you want to use it for other purposes then that's fine. If you want to use it for large architectural interiors though 600J won't go very far (I frequently use 12,200J for large sets). Just be aware that a 5 stop range of adjustment isn't always enough for portraits, you may need to use ND gels as well.

As I said earlier, if you don't have a background reflector then a wideangle (umbrella) reflector square to the background and immediately behind the subject is ususally the best bet. Reflective umbrellas can also be used, but only with 2 lights, otherwise the lighting will be very uneven. Shoot through umbrellas are useless for this purpose, the light goes everywhere and creates flare.

Your physics is a bit out, Elinchrom refer to Watt seconds not watts. In theory, a watt second gives out the same amount of light during the brief flash exposure as a watt would give out in 1 second. In reality, it's about x3 as efficient, because when a light is on for 1 second at least 3x more heat is output than light. And your maths is out too, by a factor of x3,600.

Not to worry, at least you're trying to learn the theory, it makes a nice change for people on forums to even realise that theory matters