Hello Everyone!

I'm doing a stop motion project in my university and I encountered a flicker problem during one of my shots. I am using Canon 7D + Dragonframe 3.7.1 + 1 Arri 300W + 3 Dedolights.

I have 20 Canon 7D cameras in the lab and 13 of them have flickering problems - inconsistent exposures/brightness.

Questions:

1. Were the flickering problems caused by the camera or the lights?

2. What is wrong with the cameras? Faulty? Old? Sensor overused? Turned on for too long?

3. Could the problem caused by Dedolights being near to the camera?

Do help me understand the problem. I will like to recommend solutions to my lab technicians for future classes. Thank you!

- Gerald

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Hey,

If the camera is really old or  intensively used, the shutter speed can be inconsistant.

Otherwise, in my experience (many stopmotion shoots, including 3 month on Isle of Dogs), it's more often due to lights. You should carefully test them.

Sometimes it also come from a bad electricity circuit resulting in some fluctuation in the plugs, it happened to me recently in an old building.

Try to isolate a camera that you are sure you don't have any flickering from the camera.
Then test each sources individually.

Also if you use dimmer it can be the cause if you aimed low intensity via them.

Hi,

Try covering the viewfinder with some black tape during shooting.  I can't remember why it was recommended to me for timelapse and stop motion (light leaking on to sensor or light causing inaccurate metering?), but it seems to make a difference.

I use a 7d.  It did take me going through all the menus to turn off every automatic function, to remove flicker in the camera. Some are obscure, like some sort of edge compensation, but anything that tries to "help" needs to be disabled.  Possibly some of the cameras have different settings in the menus?  Especially if used by students, or for still photos as well.  I also use manual Nikon lenses with an adapter, so I don't have the iris opening up between shots and maybe not stopping down exactly the same every frame. Kit lenses (and all Canon lenses, because they have no aperture ring on the lens) can sometimes flicker.  It is normal for still cameras to open the iris and only stop down when you press the shutter, which gives you a nice bright view.  But old movie cameras didn't do this, they stayed stopped down, at the expense of a dimmer preview.

My bigger problem is the lights responding to small changes in the mains voltage and getting slightly brighter or darker.  The camera faithfully picks this up.  I installed a double conversion UPS that smoothed out the voltage and that fixed it. (It converts AC to 12v DC, charges a battery, then converts the output back to AC, but a couple of volts lower than the power coming out of the wall.)  It is not a normal UPS, which doesn't filter the power but just kicks in if the power fails.   I tested with a volt meter visible on camera, and I could see that the frames where the needle dropped a bit (usually 1 to 2 volts) that is when I got a darker frame.  It is caused by other users in the neighbourhood, but I could also make it happen on cue by turning my oven on and off.  

At the moment my UPS battery has died and it is showing me fault messages, and I will need an electrician to come on site as it is hard wired in to my mains power.  And that will cost, so I'm putting it off. So I am shooting with some fluorescent lights.  They don't work with a dimmer, so shouldn't respond to small voltage fluctuations.  In theory.  Some seem to hold steady, some seem to change brightness a tiny bit but far less than the halogens did.  I stick a sign in front of the camera to say if the oven is on or off, and they do dim when the oven is drawing power, and not when it is off.  I think I've found enough that don't vary to let me do the animation.  (Fluoros do flicker rapidly, but an exposure of 1/2 sec or longer smoothes that out.)

Edit:  Just picked up that you have Dedolights - I think they have a ballast that smoothes the power, I don't own any but i have animated on films using them in places where I would expect dirty power, and there was no flicker.  So it comes back to the camera menus.  I might be able to look at my 7d tomorrow and see what needs turning off.

Covering viewfinder:  I used to have to cover the viewfinder with my Bolex 16mm and Mitchell 35mm if I had a light behind it, light could get in and fog the film.  But the Canon 7d is working with mirror flipped up out of the way, so you get a live view, so it shouldn't be necessary.  Also, you aren't letting the camera do any metering, you set everything manually either on the camera body or in Dragonframe, so it shouldn't be able to respond.   

 Hello, 

you know, it is quite important that lenses do not move aperture between shots. Modern camera controlled lenses open aperture between shots and close it just before shooting. This can create flickering because the mechanics of lenses is not perfect enough usually.  

I wanted to chime in on my own personal experience with flickering, and what solved it for me. 

  I had flickering when I was shooting in the following manner:

  • I was mistakenly using the 'AE' setting to film with my Canon EOS Rebel T3, instead of manual.
  • I was using the 'kit lens' that came with the camera. Even with the non-automatic switched off, I got flickering.

I fixed the problem for me by:

  • Always using the Manual mode (M on the dial)
  • using Nikkor lenses with an adapter ring. This prevents the camera from interfacing with the lens.
  • Another filmmaker, Dale Hayward, pointed me toward an AE plugin, 'GBDeFlicker' by Granite Bay, which allowed me to salvage some of the most flickered footage.

I hope this helps.

Lots of great suggestions about cameras and lights. I'll suggest a 3rd source of flicker- the animator. If the animator isn't standing in completely dark void when they're taking a frame, then they are part of the lighting scheme. Wearing dark clothes helps, as well as standing in the same spot when capturing- preferably shadowed from the scene's main light source.

Aside from that, and manual lenses- I find it's usually the mains power. Try using an LED light when testing your cameras and lights, which (I believe) don't fluctuate with your AC.

I've gone with longer exposures and have not had problems with flicker. I'm using a Canon 60D and cheap Lowell halogen lights.

Yeah, I remembered that after my post. Wear Black  shirts, and marking the floor with tape where you stand to click the frame grab can help.

My production is 100% LEDs, but I dont' know enough about LED tech to know that they  don't fluctuate.

Evan DeRushie said:

Lots of great suggestions about cameras and lights. I'll suggest a 3rd source of flicker- the animator. If the animator isn't standing in completely dark void when they're taking a frame, then they are part of the lighting scheme. Wearing dark clothes helps, as well as standing in the same spot when capturing- preferably shadowed from the scene's main light source.

Aside from that, and manual lenses- I find it's usually the mains power. Try using an LED light when testing your cameras and lights, which (I believe) don't fluctuate with your AC.

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