Variable exposure in very low light

miken · May 20, 2020

Hello all.
I'm currently engaged in a night time Badger photography project using a few LED lights as ambient lighting.
Flash is not an option. I'm using a 1DX2 and 70-200 f2.8L mk2
Things are progressing slowly but positively, I am puzzled though by the variable results in the exposures. It's as if I've selected bracketing. I attach a burst of three consecutive shots with no camera setting variations other than milliseconds in shutter actuation.
The images are SOC and I don't understand the reason for the fluctuation, it's the same in different metering modes.
Q) Am I missing something or am I expecting something outside of the equipment design parameters.
Thanks.
Mike.

neuroanatomist · May 20, 2020

What is powering the LED lights? If they’re run off the mains and use a cheap power supply, LEDs can flicker like fluorescent lights, leading to uneven exposures.

miken · May 20, 2020

neuroanatomist said:
What is powering the LED lights? If they’re run off the mains and use a cheap power supply, LEDs can flicker like fluorescent lights, leading to uneven exposures.

Thanks for that.
The LED's are 240v mains floodlight type fittings, the sort you'd have in your backyard. I'll enable the anti Flickr in red menu and see if that improves things.
Best.
Mike.

dcm · May 20, 2020

miken said:
Thanks for that.
The LED's are 240v mains floodlight type fittings, the sort you'd have in your backyard. I'll enable the anti Flickr in red menu and see if that improves things.
Best.
Mike.

I tried some outdoor floodlights for lighting the target for AFMA calibration with a 6D and noticed the flicker issue. LED floodlights running directly off 110V AC in the US can have a similar problem. They still have some internal circuitry in the floodlights, the LEDs don't run directly off house current. My setup worked just fine with I replaced the LEDs with the equivalent halogen floodlights. I haven't given them another try since I got the 1DX2.

All lights flicker, some are more noticeable than others. Did you have a dimmer in the circuit? Dimmers can also cause a flicker since they switch the light on and off, increasing the off duration to dim.

If you want to do an experiment try capturing video at 50/60, 100/120, or 200/240 fps if you have a camera capable of these speeds. Check out this short video comparing a couple of cheap LED video lights (12VDC/battery) with an outdoor LED floodlight (120VAC). Shot on an iPhone with Slo-Mo video - the easiest/cheapest way I know to check for flicker (since I already have one).

Also checked out the Anti-flicker option on the M6MII for the PAR38 and it detects the flicker from the lamp when pressing the <Q> button before you shoot. It didn't detect any flicker from the LED video lights. Neat way to test whether or not you need it. The 1DXII also tells you if there is a flickering light source.

tolusina · May 21, 2020

LEDs flicker when they are pulse width modulated rather than voltage or current controlled.
They will do this whether they are powered by batteries or mains.
The easiest, cheapest and quickest way to test is to spread your fingers and wave that hand briskly in front of the light. Spokes of a spinning bicycle wheel demonstrate this pulsing very well too.
Try it with a stepped power LED flashlight. With the lights I have here, on high power, fingers are distinct. On medium and low there's a very obvious strobe effect, multiple images of each finger.

miken · May 21, 2020

dcm said:
I tried some outdoor floodlights for lighting the target for AFMA calibration with a 6D and noticed the flicker issue. LED floodlights running directly off 110V AC in the US can have a similar problem. They still have some internal circuitry in the floodlights, the LEDs don't run directly off house current. My setup worked just fine with I replaced the LEDs with the equivalent halogen floodlights. I haven't given them another try since I got the 1DX2.

All lights flicker, some are more noticeable than others. Did you have a dimmer in the circuit? Dimmers can also cause a flicker since they switch the light on and off, increasing the off duration to dim.

If you want to do an experiment try capturing video at 50/60, 100/120, or 200/240 fps if you have a camera capable of these speeds. Check out this short video comparing a couple of cheap LED video lights (12VDC/battery) with an outdoor LED floodlight (120VAC). Shot on an iPhone with Slo-Mo video - the easiest/cheapest way I know to check for flicker (since I already have one).

Also checked out the Anti-flicker option on the M6MII for the PAR38 and it detects the flicker from the lamp when pressing the <Q> button before you shoot. It didn't detect any flicker from the LED video lights. Neat way to test whether or not you need it. The 1DXII also tells you if there is a flickering light source.

Hi dcm.
There's no dimmer being used and the enable anti flickr mode on the camera makes no difference either.
I guess it's the downside of using budget lights that are not meant for photography.

Thanks.
Mike.

dcm · May 21, 2020

miken said:
Hi dcm.
There's no dimmer being used and the enable anti flickr mode on the camera makes no difference either.
I guess it's the downside of using budget lights that are not meant for photography.

Thanks.
Mike.

I had the same thought when I tried the LED floodlights for similar reasons.

EOS 1DX2 & M6m2 manuals said:
"Flicker at a frequency other than 100 Hz or 120 Hz cannot be detected. Also, if the flickering frequency of the light source changes during continuous shooting, effects of the flicker cannot be reduced."

The Anti-Flicker feature is limited to the common AC frequencies.

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Variable exposure in very low light

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