Baby on black - How to?

A friend is bringing her baby to my home studio with very specific ideas about what she wants. I have the gear but not the know-how to get the effect she wants. She wants all pictures done with a black background and black fabric (possibly over pillows) on the floor. This I can do. I can get decent separation from the background and have several Dlite-4's and various modifiers to use for this.

The first picture she wants has the baby laying on his tummy, facing away but possibly looking back. Focus will be on the feet with a shallow depth of field to blur the rest. When I did some DOF experiments in my studio, I found that with a single Dlite-4 set to its lowest setting and Photoflex medium octa with diffusion panels and my camera set to ISO 50 and shutter speed 1/250, I could shoot at f2.0, but any larger aperture was overexposed. I was shooting with the 85L and would like to go to f1.2 or f1.4, if I could.

Also a more general question...How can I prevent much light spill onto the black fabric flooring? My light modifiers are all rather large, compared to a baby, with the exception of the Ezybox with the optional diffusion panels. I could use a grid on the light, but then the light would be a bit harsh, wouldn't it? Is there a technique for wrapping light around a small person or object that would work in this case? Thanks.

You can get bg blur at smaller apertures if you can shoot at longer focal lengths, assuming you have the space. Also I would think using medium octa will put light every where. Medium SB should be more than enough for the task.

You didn't say when this was happening. If you have time pick up a Neutral Density filter. Getting one for the lens is more convenient but more expensive. You can also get ND gels for the lights, cheaper but with them going between the light and modifier. You'll be able to get anywhere for .25 to >9 stops it's up to you.

All a grid mostly does is limit the angle of light spread. If you are referring to using a grid on a bare flash vs. a softbox? Then yes that will be harder light. But if you are referring to using a grid on the front of the softbox that would be the trick. You can also use gobos, cutters and flags to block the light .

It's happening next week (Wed). So I have a little time but not much. I have the fabric grid for the Photoflex medium octa, but although that gives me control over light direction, it still sends a wide swath of light in that direction. Maybe the small (24"x24") softbox would be best for this, but I'm still not sure how to place flags to prevent light spill on the black floor, with the baby on top of it. Hadn't thought of getting ND gels for the lights. Gee, I wonder if using my 580EX in the Ezybox might actually give me more control for this.