7D owners, help me track a flicker problem

[Jonathan Ziegler]

Hey there, what are you using to play back the frames on? In other words, you shot on the 7D, then you turned them into video in what app? If you are playing back on the 7D, don’t rely on the output, rely on something like Quicktime instead. Also, I would run all the frames through Adobe RAW or Lightroom or something that you can use to ensure you have the exact same levels on each frame and then convert to video from jpegs in Quicktime.

If I’m not getting what you mean, then please clarify. I do time-lapse with my Canon Rebel xt straight to hard drive with the built-in canon remote shooter. Sounds like there are too many factors to lay it on just one thing.

Jonathan Ziegler
https://www.electrictiger.com/
520-360-8293

[Norman Pogson]

My theory is that what you are seeing is an inconsistent iris in the lens, which is quite normal but does show up as flicker in the film because there is a slight exposure variable. Modern lenese don’t have aperture rings, the camera body sends an electrical signal to the lens to stop it down to your selected setting, being electrical you can get fluctuations.

To test why don’t you tape over the electrical contact on the lens, or put a fully manual old lens on with an aperture ring and set the aperture to wide open and run a test.

My Canon 7D Blog

[Stewart Mayer]

Hi Jonathan, thanks for your input.

I can see the shift directly on the camera, and in premiere pro, and in quickime (after importing sequential stills), and stills batch converted from raw to jpeg in photoshop and brought into premiere and quicktime. I’ve been through it all, and the actual post gurus who are animating over our backgrounds found it too (actually they found it first as they were checking the shots after each day of shooting). I’ve been shooting timelapse with DSLRs for a couple years and this is the only camera to exhibit this behavior that i’ve used, after we determined the 7d was our problem, we switched to the XS and T1i cameras for the remaining 5 days of shooting with exactly the same setup and lenses and it was fine. Do you have a 7D to test with? Any suggestions? I’m willing to try them if someone can think of something I’ve not tested for yet.

thanks,
stewart

[Stewart Mayer]

I thought that too at first, since my first test that showed it was with an electronic lens. But the rest of the shooting was done with the Zeiss ZF manual lenses that have an old school iris ring and no electronics. They are actually nikon mount but I used an adapter ring.

Rented a set here: https://www.filmstarrentals.com/Zeiss-Lenses-For-Rent-in-Boston

Do you happen to have a 7d? take a photo in manual mode with a manual lens with and without liveview on, the difference will show up every time. Or maybe it is something different? But the exposure difference is the same whether at 1/4sec or 1000th exposure so I dont think it is a faulty shutter either.

hmmmmm

[Jonathan Ziegler]

I won’t have one to play with until Saturday. It sounds like you got it to work, though. I’d talk with Canon about it.

Jonathan Ziegler
https://www.electrictiger.com/
520-360-8293

[Deleted User]

Hi Stewart: Philip Bloom may be getting similar flickering results in his timelapses. He says he’s had success using software to correct his footage in post, but I don’t know if he’s identified the root cause yet:
https://philipbloom.co.uk/2010/01/24/sky/

[Stace Carter]

I’m not sure if this is what you’re talking about, but Canon reccomends covering the eyepiece to prevent light leak when not using Live View (if you won’t have your face pressed against it).

There’s a little rubber cover that comes on the strap of the 7D (and the new Rebels as I recall) that will snap right on and should prevent any erroneous exposure adjustments.

Cheers,
Stace

Apple Certified Trainer

[Stewart Mayer]

That is one of the few simple things I had not tried, thank you. Just tried it and it makes no difference unfortunately. But, had it been the problem, I would have had to stick my head in the sand for a month.

I have canon investigating… boy, getting through their phone bank is next to impossible. Also following a few more leads, and emailed phillip bloom to see if he ever solved it. If this gets resolved i’ll be sure to post the findings/resolution.

thanks,
stewart

[James Stanek]

I think the flicker you are seeing is not unique to the 7D, but is typical of most DSLRs when used for timelapse or stop motion work. I chased this problem around on several Nikon bodies, and since then, I’ve seen confirmation in several timelapse oriented website discussion groups. The flickering is caused by the iris. On modern DSLRs and SLRs, you may set the iris manually, but the camera will open it all the way between shots, so you get the brightest viewfinder to see through (and for the autofocus system) while composing. Then, when you press the button to take a picture, the mirror swings up, the camera stops the iris down to the selected f-stop, and the shutter activates.
The problem for stop motion work is that the iris never stops down to the exact same place twice. This error is well within the tolerance of what is needed for still photography, which is what the camera is built for. However, when you play the frames in sequence, your (very sensitive) eye sees this tiny variance in exposure as flicker.
Regardless, it’s relatively easy to determine if this is your problem. Make a series of tests at different f-stop settings. The problem should go away when the lens is set to it’s maximum aperture. It should get progressively worse as you stop the lens down further towards F/16.
Fixing it is harder. You can shoot wide open all the time, which limits depth of field and generally requires NDs for adjusting exposure time. You can shoot nearly wide open to minimize the problem and live with it. You can try one of the various flicker correction plug-ins. Personally, I haven’t had much luck with the plug-ins, but I haven’t tried the newer ones. Try checking out some timelapse on DSLR forums for more info. I only periodically skim them myself, so I don’t have any particular ones to rec.

[Mathew Joki]

Make sure that “Auto Lighting Optimizer” is OFF and “Highlight Tone Priority” is OFF.

See if that helps.