Q:

How can I further decrease the exposure in a studio environment?

I was trying a few things yesterday involving a studio backdrop which was lit using a grid to provide a gradient effect and a subject about 3ft in front of it, with its own lighting through umbrellas.
I was having problems with the shot being over-exposed. I had my studio lights on the lowest possible power setting, ISO-100, a shutter speed of 250 (the max sync speed) and my aperture was f/22 which is the highest it will go.
I don't really want to have to use the highest possible aperture value, and would like a bit more room to adjust it. The background was so detailed that you could see the paper texture which would had been better blurred out slightly.
Is there any way that I can further adjust the light input so that I have more flexibility with my settings?

A:

I think the approach will depend on several things: if the light is soft or harsh, if the overexposed illumination is over the entire scene or just a part of it.
ND Filter
If the entire scene is lit then you can try using a ND filter. If you use a 4x ND filter you can reduce the exposure from f22 to f11 or with an 8x to f8. A polarizing filter will also cut light if you don't have reflective surfaces or already polarized light.
Soft light
You can try using ND gel filters for the lights. You can also use wax paper to lower the light on individual strobes. Put the paper or gel over the flash head. Just be careful to ensure that the paper you are using doesn't change your white balance.
Harsh light
You can use a cardboard of black paper to make a mask on the light and move your lights further away. Twice the distance = 1/4 the light. Use the cardboard to maintain a similar shape regardless of the light distance.
The gel flash filters can also work but probably can scatter the light a bit. The wax paper option will diffuse it, but it is still an option if you have a considerable distance to your subject.
The cheaper way
Just put your lights further away.

