How do I control spill from main light onto (colored) backlight?

Just got my colored gels and started playing with lighting up the background with different colors. I have a problem with the main light overpowering the background color though. Obviously I could position the main light in such a way that little or no light reflects in the direction of the background, but not only would that really hinder the main light to be used effectively but it is also almost impossible due to space restrictions.

So I'm guessing I should start experimenting with gobo's?

Or is it just down to power ratios? Full blast on the background flash and limit the main? I have yet to finish up my potentiometer mod on my 283 so I have difficult attaining that right now.


PS, I will post a picture later, I don't have internet at home right now.

a photo would help, or at least a diagram or explanation of how you have your lights set up.

you could try to use grids on your main light as well to help direct it more to the subject

Get your subject as far away from the background as possible and get your key light as close to the subject as possible - this should reduce light spill enough for you to control the background with a seperate BG light but some spill onto the background is usually unavoidable.

If you are shooting in a small area then try to use controlled modifiers like grids for accent-lights to stop light bouncing about everywhere.

If all else fails, paint the room black

Use a dark colored BG (and add more power to the BG light).
Keep the main light off the BG as good as possible.

The closer the light source is to the subject the less "light depth of field". You'll get a much faster fall off and less contamination of your background.

So like Hermes said get the light that is spilling as close to the subject as possible. The reason, by the way, is better explained by this guy than me:

http://strobist.blogsp​ot.com …12-position-distance.html

I forgot to say this was with a white paper tablecloth as BG. My rugged wetsheet ended up being not so rugged after all. I'm looking to buy some gray seamless paper, it's just that it is very expensive where I live and that's one thing I can't order cheaply from the US and A (because of shipping restrictions).

Yeah I did try and get the subject as far from the BG as possible, and the light as close to it as possible.

That's easier said than done in a tiny all-white room (with only basic equipment) though. I could fiddle with this in our (public) garage, but because I want to learn how to do this stuff as well as possible under the least favorable conditions I strive on in my tiny bedroom. I'm sure a lot of you guys could cope with these limitations and that's what convinces me to try and master that as well.

Try a black background and a relatively strong background light.

If I were in your position the first thing I'd do would be to paint the walls mid-grey - light spill would be less of a problem and you'd most likely be able to use the wall as a background.

Trying to achieve controlled lighting in a small all-white room for anything other than high-key work is really going to be an endless uphill struggle and without sample images and an idea of your setup its difficult to suggest anything specific.

You could always use a flag or something to block the spillover light onto your background.

Distance!...if you double the flash-to-subject distance and make that the flash-to-background distance, the light striking the b/g will be -1EV compared to its intensity on the subject. 4x the distance is -2EV the intensity on the b/g compared to its intensity on the subject

Using an umbrella in a small room with while walls and ceiling is almost imposible to control spill to the BG. I have better luck with a small softbox with grid though.