why the flicker, why the flicker???

[CaesarC]

Just the other day I had a small problem. It was no big deal, everything in the end worked out just fine, but I wanted to see if anyone had any idea what caused the problem. Below is
Camera set up:

Red
Build 20.1.6
48 FPS
23.98 time base
180 shutter
redcode 36

Lighting was all 3200 with:
2 4 bank kino's
one source 4
one Arri 300
and a single kino tube on the floor
Also, 2 common desk lamps, both on dimmers.

Problem:
One of the desk lamps flickered. The dimmer was replaced, and the flicker didn't go away. Also, while on the dimmer, the lamp was full up, and still flickered. Removed the dimmer from the set up and the lamp still flickered.

I switched the shutter to 288 and the flicker went away.

Anyone have any input or shed any light on why this happened?

Thanks,

Caesar

carnevale43@yahoo.com

 

[David W. Jones]

Also, 2 common desk lamps, both on dimmers.

When you say common desk lamps, what type of lamp was it?

 

[CaesarC]

The lamps were no different then the type you would put in a 3/4 year old kids room. Nothing out of the ordinary. Desk/side table lamps.

 

[ericyoung]

Fluorescent energy saving bulb? Was the flickering visible to the naked eye?

 

[Noah Kadner]

Totally normal for certain practical lamp/electrical cycle combinations to flicker at certain shutter angles. Fixing with the shutter or swapping out the lamp is the best way to fix. I.e. you did exactly the right thing.

Noah

 

[Cail Young]

48 FPS
23.98 time base
180 shutter

You were shooting with a shutter time of 1/96 which doesn't fit neatly into the (probably) 60Hz power cycles going into that lamp.

1/120 would have worked fine, as would have 1/60.

When under/overcranking with funny light sources you may be best to switch the shutter to NORMAL mode and display to 1/SEC so you can accurately set a precise shutter time as opposed to a shutter fraction or 'angle' - for example we did a TVC yesterday at 22FPS - work out the angle on that to get 1/50 shutter time (50Hz power in Australia). (I believe the camera displayed 158° when I changed it over to 1/50 NORMAL).

 

[David Mullen ASC]

I've had ordinary tungsten bulbs flicker on a film camera running at 24 fps crystal-sync due to a bad power supply in a poorly wired house.