Studio Lighting Help

[Diddy2theJJ]

Hey guys,
I feel like I have a fairly good grasp on outdoor lighting, but I'm having some problems with studio lighting. I just rented some small studio space to start working in. I can get a nice seamless white background by using the method that I read about here:

I've moved the blog –> zackarias.com/blog » White Seamless Tutorial :: Part 1 :: Gear & Space
It was very helpful. My photos aren't looking quite as nice and evenly lit though, and I'm wondering if my light is too small. It's a 24x36 softbox over an Elinchrom 400w D-Lite. I'm also having problems with getting the background to be darker. It comes out as a lighter shade of gray when I turn my background lights off and use only the softbox. I thought maybe my space is just too small in there, but when I looked at the tutorial posted above it doesn't look like that area is much bigger.

It's not done yet, but here's a pic of the initial studio setup:

 

[tirediron]

What settings are you using? Are you increasing your shutter-speed to help control the background colour when you want a darker shade?

 

[Big Mike]

If you want your background to be dark/black, then you need to keep as much light off of it as possible. It also helps to remember the inverse square law.

In your example, the softbox is pointed at the subject, but it's also pointed at the background...so there will still be some light reflecting off if the background...making it grey and not dark/black.

Hard to judge the distance, but it looks like your subject is maybe 6-8 feet from the light...and your background is another 6-8 feet behind that. So the distance to the background is twice as far as the distance to the subject. So using the inverse square law, we can determine that the background is getting about 1/4 as much light as the subject. 1/4 as much light, is equivalent to two stops, by the way. Not considering that the backdrop is highly reflective (white) it doesn't take much for it to show up as grey (brighter than black).
Also consider that your backdrop, as white paper, is characterized by diffuse reflection. That means that any light source in the room will be picked up and reflected by the the backdrop. So not only your light in the softbox, but light bouncing off of the walls, the floor etc.

So to get around this, there are a few things you can do. The main thing is to use the inverse square law to your advantage. For example, if you move the light to 2 feet away from the subject, while keeping the subject just as far from the backdrop, you change the ratio. So instead of being twice as far from the light, the background might then be 4 times as far from the light. The inverse square law tells us that it would then get 1/16th the amount of light (4 stops). This would probably be enough to render it quite dark.
As you can probably guess, if you moved the subject even farther away from the backdrop and moved the light closer to the subject, you can maximize this effect.

Another thing you can do, is to aim your lights so that they don't directly point at the backdrop. This is where softboxes come in handy. So instead of firing right at the subject, put the light more to the side and turn it so that it's only turned toward the subject, as much as it needs to be. This is also why it's nice to have a grid for your softbox/lights. It helps to keep the light pointed in one direction.
You could also put something on the far side of the set, to prevent the light from bouncing off of the white walls. (doing dark field photos is much easier in a dark room, than it is in a white walled room. You might consider something like curtains to cover the walls, if this is something you plan to shoot often.

 

[Diddy2theJJ]

tirediron, I'm at my sync speed with my camera, so yes the shutter speed is cutting out as much light as possible. When I turned all my lights off I only get a black picture so there's not external light filtering in there.

Big Mike, your comments are much appreciated. I may have to check out some black curtains for the walls. I don't mind some light bouncing during portraits, but for newborn photos I like it to be pretty dark except for the subject. I will try and experiment with distances and using the inverse square law. I've read about it a little bit and it's finally starting to make some sense.

Thanks again.