Multiple takes of the same scene at different exposure values — safety net for color grading and HDR. Rescue option when your key shot flattens in post.
Exposure Wedge
You need exposure wedges when you're not 100% sure if your exposure is correct—or when you consciously want to offer multiple options. It works like this: You set up the camera on the subject, take a shot at your base exposure, then one at +1 stop, then one at -1 stop. Sometimes also +2, -2. All three (or five) versions go onto the same material, same lighting situation, same camera settings—only the exposure changes. This is your insurance.
On set, you don't need special equipment or extra time for this if you're organized. With ND filters or just by changing the aperture, you can do this in seconds. The exposure wedges all land in the same take or in directly consecutive frames. You don't shoot three separate takes—that would be inefficient. In the edit or color correction, you then have three source materials to choose from if one version becomes too dark and another too bright. This saves you discussions with the DI suite when the colorist says, "The material is underexposed." You can then say, "No, I have the +1 version for you."
Exposure wedges become particularly valuable in HDR productions. If you shoot in SDR but need to convert to HDR later, you need highlight information that you might have lost in the base exposure. The overexposed version (+1, +2) saves your skies, windows, and reflective surfaces. The underexposed version (-1) is your safety for shadow detail if the colorist later determines in the DI that the blacks are washed out. So, you're not working with one take version, but with an arsenal.
In practice: Never shoot without wedges in critical scenes—especially for exterior work, in locations with extreme light range, or for talent shots where a failed take is costly. Make sure to note exactly which stops you made in your shot log. The DI team needs to know that versions 3, 4, and 5 of the same shot are different exposures, not errors. A good workflow system (similar to color timing or monitoring) recognizes these variations and sorts them clearly. Exposure wedges are not a flaw in the staging—they are professional foresight.