taking one frame at a time since 1999

Getting ready to film a feature and I can't get rid of flickering issues. Have been watching Youtubers and reading blogs so I've blacked out everyting, using LEDs, have cranked my Fs up high as they will go and my SS down to the point of blowing out the picture (but found my best results at F11 and SS 1/3) on my Sony A77 with Zeiss 85mm. Still have some issues...see attached. Nothing auto is turned on. Any advice?  Thank you in advance.

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It looks very much like the flicker I got that turned out to be due to small fluctuations in the AC power.  I used an old analog  multimeter in front of the camera to test it.  It was clipped onto the mains power that powered the lights. Voltage shown on the meter varied by around 1 volt,  and the lights got dimmer when the voltage dropped, and brighter when it went up.  I had just had a studio building built in the back of the garden, and fitted it out with lighting bars and power points on the ceiling, all ready to animate.

If you don't have a meter, I also found that the 220-240v AC mains power was pretty steady at 1:00 to 5:00 AM, but varied a lot during the working day when factories in the neighbourhood were turning equipment on and off.   So if you don't get the flicker then, but do in the day or when turning off something power-hungry like an electric heater, it might be due to power fluctuations.  If your lights respond to a dimmer, then they will also respond to a small drop in the voltage.  I could make it happen by switching the 1200w oven in my studio on and off, in order to test it without waiting for others to cause the voltage variations, and I also knew which frames I had the oven on for.  But, inducing flicker this way does not completely eliminate other possible causes. 

I don't know the Sony A77, I have Canons, and there are a lot of sneaky items on the menus to check - one might have been called Edge Correction, or something like that. Any "helpful" thing that uses the cameras pea brain to "improve" your still photo for you is suspect.  I also needed to use older Nikon manual lenses with the aperture control on the lens itself, and which could be partly unscrewed (on a Nikon camera) or used with an adapter (on a Canon) so it did not open up between exposures, as is normal for still cameras, and could not be controlled electronically by the camera body.  So there might still be possible camera causes for flicker that you need to eliminate.

My solution was a power conditioner - an Eaton Powerware double-conversion UPS that converts the AC power to DC, charges a battery, then converts back to AC, losing a couple of volts in the process but making the output absolutely steady.    Mine is a wired in 4000 VA unit, because I already had the special overhead lighting circuits as part of the building's wiring, and it cost about $5000 with installation by an electrician.   A better (and cheaper) way is a smaller 1500 VA stand-alone, plug-in unit, more like $1500, and with more than ample power now that we have LED lighting.  I was using a mix of halogens at the time, some up to 1000 watts.  Now I use smaller lights.  

A normal UPS does not filter the power, it lets the variation through, and kicks in to replace the power if it cuts out completely.   I tried one, costing around $100 - completely useless for this purpose.  Great if the computer is rendering overnight.

Some animators use a thing called a Variac, where you manually adjust the voltage output before shooting each frame - you set your output to a little lower than the lowest the incoming voltage is likely to get to, and the higher it goes the more you turn the dial down to keep output at the same level.  Another fiddly thing to do while animating, which you don't want, but apparently it works.    

Thank you, Nick. Have you ever used the program "Flicker Free"? Any thoughts?  Testing a bunch today. May have to go down to a rental house and get a lunch box.

Have you dimmed your LED lights? They work on PWM, which basically turns them off and on so quickly the human eye only sees a dimmer light. Some cheap LEDs do it quite slowly. You can get 10K PWM dimmers, which switch at 10,000 times a second.

Have you also done tests with just a single light at a time, to see if it is only one of them creating a problem? That might help to eliminate one possible cause.

I appreciate your reply. I built all the light rigs myself based on a Roger Dekins model, but I didn't include a dimmer option and am now regretting it. Thank you for responding. I've purchased Flicker Free and did some testing on it today. Seems to work. We'll start principal photography tomorrow.

Flicker Free type software works pretty well if it is an overall change in brightness with all lights changing by the same amount.  Or with the exposure in the camera being changed. I tested one, as a plug-in for After Effects, Flicker Fixer I think -  just a demo version with watermark.  It didn't work for me because I had some fluorescent lighting on, for a general soft ambient light, that did not change with the voltage fluctuations.   But the halogen key lights and backlights did change, so if they went dimmer and I boosted the brightness to get them back to the same level, the ambient fluoro light got too bright.  In the end, with stuff already shot, I had to erase most of each frame to replace it with a single image, so only the moving puppet had the lighting changes.  I made some adjustments to the brightness and contrast on the puppet part of the image manually, frame by frame, in TV Paint, but it could never be perfect. However, since the character was moving, the changes weren't as noticeable as they would be with a static background.  But it took longer to fix in post that way than it did to do the animation in the first place.

Your footage did look like an overall exposure change, rather than just one light changing.  So that points to something in the camera, or something that affects all the lights the same.

I know that fluorescent lights don't respond to the old type of dimmer that just reduces the voltage - they usually stay the same until the power drops too far, then go very dim, shut off, or develop an obvious flicker.  (They do flicker anyway, but very fast, so a longer exposure of 1/2 second or longer averages them out.)  I don't really know much about LEDs, but if they have a similar rapid switching on and off, a longer exposure might help with them as well. I would try 1 second. The dimmable ones need a special dimmer like Simon was talking about, not the old style dimmer that lowers the voltage.  I need to google PWM and learn what that means!

It is still possible that the camera is doing something to "improve" each frame on an individual basis, as if it were a still image.  I looked at the camera support on the Dragonframe site, it has the set-up instructions for the Sony A77 II:

No mention of an A77 I model.


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