Ok, we all know that the maximum apeture usually between 1.4 and 4 let in a ton of light and have a shallow depth of field. The minimum aperture, usually 16 to 22 lets in very little light and has a huge depth of field.

So when we are using huge strobes we use the F stop to either lighten or darken photos. These shots were taken to show the differences and are unedited.

We move form F9 to F18. Notice how the face shadowing gets darker and contrast greatly increases. Lighting was done at 120w coming in from the upper left about three feet away and elevated 2 feet above via a reflective umbrella