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darkening background in limited space
http://www.paulcbuff-techforum.com/viewtopic.php?f=8&t=4023		 Page 1 of 1
Author:  shutterdown [ Sat Apr 20, 2013 8:06 pm ]
Post subject:  darkening background in limited space
First, I should describe what I have for equipment and space, for a studio-like environment.

I'm a novice. I have a finished basement, and use part of it as a studio. The ceiling is about 7 ft 4 inches. Spray texture. Carpet on the floor. The room is 11 ft wide, 26 ft long.

I have a couple of PCB light stands to hold up a 9 ft rod, to hold backdrops.

I have three PCB strobes, and I've set them up in such a way to mimic the "3 light" configuration.

I typically have a subject stand roughly 6 ft from the backdrop. To the camera right, an Alien 800 with a 24-36 soft box, with the light stand up against the right wall. The angle to the subject is roughly 45 degrees, and works out to about 5 ft from the front of the softbox.

The second strobe, also an Alien 800 and same soft box, is 5 ft from the subject on camera left, but the light is up as high as I can get it (vertical orientation), and pointed downward slightly.

In the back, to camera right, in the corner, I have an Alien 400 with a strip box, for use as the rim light. Slightly pointed downward. It's roughly 6 ft from the subject.

I trigger these with pocket wizards. Both 800s are at half power.

I shoot with a full frame camera and can only use certain lenses, as you might expect. Otherwise, I can't get back far enough to frame the subject properly. It's particularly difficult with group shots, since I don't have the length or height to work with, with the backdrops.

But, here are (at least) two issues I'm up against. I can't get the background to be very dark, since the strobes end up being too close and light it up almost as well as subject. I'm also wondering if this set up hinders me getting the eye color to "pop." I'm able to light the face up, but it seems like the angle of the strobes prevents better on axis lighting of the eyes. Or, am I wrong about this particular aspect of it?

I put my camera (Canon 5DII) in manual mode, typically f/8 and 1/160-200 second, ISO 100. I do have a light meter, and check it, and it seems correct. The histogram looks uniformly good, but the background is too light. Backgrounds are mottled, usually, and can be bluish, brownish, and other darker colors. Background blur is not very great, but acceptable.

Because of the brighter background lightness, I often "create" a darker background by duplicating the image as a layer in Photoshop, darkening one layer, then erasing the area over the subject. But, this is painful and I hate doing it.

I also tried a grid on the 800s, to better direct the light toward the subject. It doesn't help much in my circumstances.

Given these conditions, I'd appreciate any suggestions for improving things. Thanks.

Alan
Author:  John Skinner [ Sun Apr 21, 2013 1:44 pm ]
Post subject:  Re: darkening background in limited space
This isn't really PCB gear related (IMO) so I'm going to be very brief here.

You should familiarize yourself with the inverse square law. You can take any background(even white) and make it black providing that the lighting ratios are correctly working together. Google Frank Doorhof and check his site for "meters". He has very easy to understand info on the ISW and light meters (both methods) there.
Author:  Pxlwz [ Sun Apr 21, 2013 2:10 pm ]
Post subject:  Re: darkening background in limited space
Things you can try:

- Bring your front lights much closer to the subject: Example: if your light was 5' away from the subject, and 11' away from the background, you will get ~1/5th of the light measured at the subject to reach the background (or around - 2 .5f-stops.) If your light is 2 feet away from the subject, but the subject is still 6 feet away from the background, your backdrop would get about 1/50th of the amount of light, that hits the subject:
http://photo.tutsplus.com/articles/ligh ... quare-law/
However, your soft boxes will also give much softer light, the closer you bring them to the subject.
If it is too soft, and you don't have smaller modifiers, you can try to cover part of them with fabric, black cardboard etc.

- Try to use grids on your soft boxes.
- Flag your soft boxes.
- Hang some dark grey or even black fabric or tablecloth alongside the wall, to reduce bounce light towards the background.
-Paint walls and ceiling with a neutral gray.
Author:  shutterdown [ Sun Apr 21, 2013 2:47 pm ]
Post subject:  Re: darkening background in limited space
Pxlwz, thanks for the useful tips.
Author:  kenyee [ Sun Apr 21, 2013 9:17 pm ]
Post subject:  Re: darkening background in limited space
shutterdown wrote:
I also tried a grid on the 800s, to better direct the light toward the subject. It doesn't help much in my circumstances.


Are you gridding your B800's and not using anything else that's gridded?
You have to grid everything...
Author:  shutterdown [ Sun Apr 21, 2013 9:50 pm ]
Post subject:  Re: darkening background in limited space
The strip box in the back corner is not gridded. It's not pointing at the background, and the angle is severe enough, I don't see much light hitting it. Plus, the power level is pretty low on the AB400, just enough to lighten hair.

The only other strobes are the AB800s.

I did move the two 800s closer to a test subject, and the background darkened up, as expected. I'll keep experimenting.
Author:  kenyee [ Mon Apr 22, 2013 4:31 pm ]
Post subject:  Re: darkening background in limited space
shutterdown wrote:
The strip box in the back corner is not gridded. It's not pointing at the background, and the angle is severe enough


You might be getting light bounced back from the walls/ceiling given the size of your space.
If you have a spare dark/black bedsheet, hang it on the walls opposite the lights. Moving the lights closer to your subject sort of simulates this via the inverse square law, but you can avoid it by using black to absorb the light...
King size bedsheets are pretty cheap to buy..
Author:  Technical Support [ Tue Apr 23, 2013 11:21 am ]
Post subject:  Re: darkening background in limited space
Good advice posted here. But to add, you say you do not have very good background blur, but you are at half power and f/8. You have plenty of room to open the aperture and still dial the power down on the lights. You may be limited to how much farther you can go on the 400, but that can be gelled or use black lace fabric to reduce the light coming from it.

I assume you are using a black background vs. a dark grey or even lighter color?

As for eye sockets, the direction of the light dictates this, so have them face in the general direction of the key light. You can also move your fill closer to the camera axis.

Are you going for contrasty or softer light? You can feather the light to skim across the face. This will aim the light off the back ground, so it gets less light.

Also, 11' is really narrow, especially for groups. I won't say it cannot be done, but it is going to be hard.
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