Rolling Bands and Shifting Skin Tones at a Sangeet
Rahul is shooting a sangeet function in a community hall for a client's three-minute highlight film. The hall is lit by old 50 Hz fluorescent tubes plus two warm halogen spots aimed at the stage. His camera is set to 1080/25p, auto exposure, auto white balance and auto ISO. On playback, the ceiling lights show a rolling dark band, faces shift between magenta and green as he pans from the tube-lit seating to the halogen-lit stage, and cheeks near the spots are blown out. He also wants a two-second slow-motion shot of a dancer's leap for the opening. His 64 GB card shows 12 minutes remaining, he has one spare 32 GB card, an ND filter, a grey card, one small bi-colour LED panel and no light meter. The best part of the evening is still to come.
1. Diagnose the rolling band and the blown faces, and give the exact camera settings you would lock in.
Read the worked answer
The band is a shutter/mains mismatch, made worse by auto exposure. Fluorescent tubes in India flicker at 50 Hz, so brightness rises and falls every 10 ms. When Rahul pans toward the halogen spots the auto system brightens the image by shortening the shutter - possibly to 1/500 s - and each frame then samples a different part of the flicker cycle, producing a dark band that rolls through the picture. The blown faces come from the same auto system metering the whole frame: the dark seating area pushes exposure up until the lit faces clip.
Lock these in:
- Shutter: 1/50 s (the 180-degree rule for 25p). This also integrates over a full mains cycle and largely removes banding. If some banding survives, use the camera's flicker-reduction or synchro-scan setting.
- Exposure: manual. Set aperture and ISO so faces on the stage sit just below clipping; use zebras or the histogram rather than the LCD in a dark hall. Use the ND filter if the halogen spots are too bright at a wide aperture.
- ISO: fixed, at the highest value that still gives acceptable noise - do not let it float, because auto ISO changes both noise and colour between shots.
- White balance: manual, not auto. Grey-card the tube-lit seating, or set the tungsten preset and let the halogen read warm as an accent.
Locked settings produce consistent footage; auto settings produce three problems in one take.
2. How do you handle the mixed fluorescent and halogen lighting so that skin tones stay believable, and what do you shoot for post?
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Mixed sources cannot all be made neutral at once - the decision is which source becomes the reference and which is allowed to stay warm.
Practical approach:
- Choose a reference. The fluorescents cover most of the room, so white-balance to them on the grey card. The halogen stage will then read warm/amber - which is acceptable and even flattering on skin, whereas the reverse (neutral halogen, green faces in the seating) looks wrong.
- Reduce the gap at source. Bring the bi-colour LED panel to roughly the halogen colour temperature and use it as a soft fill on faces near the stage, so the transition across a pan is smaller.
- Stop panning through the boundary mid-shot. Cut between seating and stage rather than whipping across two colour temperatures in one continuous move.
- Beware the green spike. Fluorescents often render skin slightly green even when technically white-balanced; check on faces, not on a white tablecloth.
Shoot these for post: ten seconds of a grey card or colour chart under each lighting condition, at the start of each block; a locked-off wide of the hall as a reference; and clean plates of the ceiling and stage. In the edit, correct per shot - never mid-shot, because a correction that fixes the pan will crawl. Small, consistent corrections on short clips look far better than one heroic grade across a mixed take.
3. Rahul wants a two-second slow-motion leap but has 12 minutes on the 64 GB card and a 32 GB spare. Work out the shooting and card plan.
Read the worked answer
Slow motion first. The film is going to a 25p timeline, so the shot needs to be recorded at a higher frame rate and played back at 25p. At 50 fps, two seconds of screen time needs one second of recording and gives 2x slow motion; at 100 fps, it gives 4x. Rahul should pick 50 fps - 100 fps usually needs more light than this hall has.
Exposure consequence: to keep the 180-degree rule at 50 fps he needs a 1/100 s shutter, which halves the light reaching each frame compared with 1/50 s. That is about one stop. He must open the aperture, remove the ND filter, or raise ISO - and he should test it on the dancer before the performance, not during it.
Storage consequence: doubling the frame rate roughly doubles the data per second. Recording the whole evening at 50 fps would burn through the remaining card. So: keep the bulk of the shoot at 1080/25p, and switch to 50p only for the specific performance he wants slowed, capturing a few short bursts of 5–10 seconds rather than one long take.
Card plan:
- Protect the 64 GB card and keep the 32 GB as the working card for risky/high-bitrate material.
- Offload at the interval to a laptop or portable drive, verify by playing clips back from the copy, and only then reformat.
- Never format a card that holds the only copy - the leap shot is unrepeatable.
If there is no offload device, drop the recording bitrate or resolution slightly rather than risk a full card at the wrong moment.