5D mk ll Liveview error?

[Leopard Lupus]

Hello there!
Last evening I was shooting a very low light concert with a 5D mk ll, Canon 50mm f/1.2 and 430ex ll.
When using liveview for a few manual focusing shots, I encountered a weird behavior from the camera. When not focused on light at f/1.2, the liveview would show transparent moving bars (like the fuzz on a TV channel that is black and grey) which was rather annoying. I was previously standing outdoors with the camera around my neck in 30degree weather, but I have placed it in worse conditions than that.
Has anyone experienced this before?

[tt]

Were you shooting video? Could have been your frame speed wasn't in tune with the frequency of the power supply so it was flickering? (Not sure if live view in photo mode would have the same issue or if you can even change the live view Hz?)

[KacperP]

Has anyone experienced this before?

Yes. I have the same in my 60D. Camera electronics probe image at speed set for shutter and try to emulate expected result. It happens when shutter speed is faster and close to one of harmonics of lighting frequency. It's not an error. I think this can be actually treated as feature, some kind of warning indication

As for lighting frequencies, they can be very different. Metal halide and fluorescent lamps with magnetic ballast flicker with mains frequency, more advanced fluorescent ballasts use much higher frequencies, and with LED lighting it solely depends on its power source - some flicker with mains, some at few kHz, and some does not at all.

[Mt Spokane Photography]

It has happened to all my 40D's my 7D, my and my 5D MK II.  Using a AC adapter helped when I had the camera in liveview for more than just a few minutes.  It could be the battery drain is lowering the battery voltage, or sensor heating, or a combination of things, but it seems to happen to most Canon DSLR's with liveview.  Come to think of it, I don't recall it happening to my 1D MK III and its much more powerful battery.

[Nick Gombinsky]

As they've stated, its not an error. Different kind of lights oscillates at different frequencies (they tun on and of a certain amount of times in a second), fluorescent tubes and such, with magnetic ballasts, oscillates at the frequency of your power grid (220v = 50hz // 110v = 60hz). For it not to show on your camera, it must have a shutter speed equal to the Hz of it, or, it must be a number equal to the base Hz multiplied by a natural number (1, 2, 3, etc). It happens on TV screens also.

The thing is that nowdays, many light fixtures uses an electronic ballast, which, in theory, oscillates at such a high frequency that the camera shouldn't be able to pick it up. But not every manufacturer uses good ballasts. So sometimes it is really hard to find the right shutter speed. It has happened to me with many stage lights, I flicked the shutter dial everywhere in live view until I got the effect toned down the most, but I couldn't remove it all the way. This applies a lot when it comes to LED lights. They are a bitch.

[KacperP]

This applies a lot when it comes to LED lights. They are a bitch.

I studied lighting engineering and I work in entertainment lighting industry, and I know a bit more about those.
Your problem is not with the LEDs themselves, but their power regulators. Cheap one usually flicker with mains frequency and with different PWM modulation ratios - those are real pain.
There are ones that have PWM regulation around 1-2 kHz for flicker-free light in TV cameras.
There are also LED lights with constant current regulation which does not flicker at all.

[Leopard Lupus]

Thank you all very much for the explanations, I was terribly worried!
I am actually looking forward to learning more about lighting, as I have always been against anything that is not natural lit. This helps a TON.