[Cycle] Shadow from spotlight without lighting the environment

Hi everyone,

I’m a beginner Blender user, and I started a few days ago to use Cycle.
Everything is going fine but I’m facing a problem with lighting:

I have a scene (white lightbox) with different lights. It’s very diffuse and smooth.
For a special effect, I would like to have a strong shadow of my subject, but I do not want to add more lighting to the subject and to the environment.

I tried different thing with the light path, but all suggested solutions added more lighting to the close environment of my model.

How could I say to my light “cast shadow only, not light” with Cycle ?

My apologize if you consider it as a repost, but I did not find the adjusted answer to my problem.

A screenshot of what you have or a link to your blend file could help in this case.

If you are using a mesh lamp, the closer or the larger the lamp, the stronger the shadow, if I remember correctly. With the blender lamps, the smaller the size value, the stronger the shadow and this doesn’t affect the light strength, I think.