Lighting Ratios

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    Mustafa Irshaid

      Hi there,
      I’m Wondering how DPs keep a consistent lighting ratio throughout the whole piece.
      Or don’t they? I don’t know.
      Key to fill or Key to background ratio

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    • #214540

        I’m not sure what exactly your question is. Using  a light meter or false color will make it fairly easy to adjust your ratio as desired in every shot. So if you want to stick to the same ratio in every shot, that’s how to do it. But I don’t see why a DP would want to stick to such a hard rule. Every shot is different and might need a different feel and therefor lighting and lighting ratio.

        Tyler F

          It definitely varies as each scene mostly likely is different. Night vs. Day. Interior vs Exterior, etc. Sometimes you don’t have control and have to lean into those obstacles.

          What you can do is, let’s say you want to shoot at a t/2.8 the entire time. Then maybe your subject at key is always a 2.8. You can modify through lighting or in camera via ND, shutterspeed/angle, ISO..then work from there.

          Maybe the fill or shadow side of your subject always lies at a t/2 or 1.4, then adjust accordingly. Same goes for background or practical’s.

          A light meter is your best friend, buy a combo if you can! I think Roger (and myself) own the Gossen Luna Pro which have both. Cheap to find and take a 9v battery.



            “I’m Wondering how DPs keep a consistent lighting ratio throughout the whole piece.
            Or don’t they?”

            I don’t think they do (unless there’s a specific reason to). They keep it consistent throughout a scene.

            If a couple says farewell to each other in tears in a dim barn, and then one of them steps outside into a desert at noon to face the antagonist, there’s not much reason to stick to the same lighting ratio I would think. But the wide, medium and CU shots inside the barn must match each other.


              You’re mainly trying to be consistent within the coverage of a scene. Individuals in a space may be in different lighting ratios but when you go from a wide shot to closer shots, you try and make it feel similar in contrast. If you’re cutting to a reverse angle not seen in the master wide shot, you are more free to create a different effect.

              You can use a light meter of course if you are concerned. Often you light a master  –let’s say to f/2.8 — and when you go into coverage, you might adjust the light on the actor but not touch the background light so if you light the actor to the same level as the master, then the background will look the same as before. The ratio you often set by eye, especially if you are going for that “barely visible” level of fill. But you can use a light meter or tools like false colors, waveforms, etc. if you’re not sure.

              If shooting digital with a DIT on the crew, you can also save a frame of the master shot and compare the new set-up to see if they are in the same ballpark — do an A-B comparison.

              M Ryan

                This one was a helpful guide for me in using false colour to help with consistent ratio

                Cinematography School: Lighting Ratios 101

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