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Old May 18th, 2010, 06:25 PM   #1
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Strange slight flickring problem on 5d mark ii

Hello,

for some quite time now, I've noticed that when shooting static interviews (for example) there is a very slight an gentle flickering issue, mostly noticeable in dark areas. of course the camera is on full manual, tripod, and the lighting is studio 3200K lamps, that should not cause any flickering issue (25p at 50hz).

Attached is a 4 seconds clip with some flickering (mostly noticeable in the dark left down corner of the frame).

does anyone knows what causes this issue and how maybe to solve it?
does it has to do anything with LCD auto brightness feature (should have, but maybe a bizarre bug)...

Thanks in advance,
Alon.
Attached Files
File Type: mov flickring-issue-5d.mov (656.0 KB, 855 views)
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Old May 18th, 2010, 11:01 PM   #2
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I really looks like your f-stop or shutter speed is changing OR you're on auto ISO. So maybe an accidental twist of a dial? It has that "pop" in exposure I see when changing one of these on the fly. It doesn't look like what you get when you're lighting and shutter is out of sync. And I don't see you zooming, which would be my other guess if you where using a variable aperture and zooming. I can't remember if highlight tone priority can do this, I don't think it adjusts while recording.

Auto LCD isn't the culprit since it's brightness is totally independent of what's being filmed. Although I highly recommend you always set your LCD brightness manually for every situation you're in by using the exposure bars in manual mode.

Lastly, do you see this on your camera's LCD screen during playback? If not, then it's something happening in post.
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Old May 19th, 2010, 04:27 AM   #3
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Of course everything, including ISO, shutter, IRIS was set to manual.What I sent was a very short example out of a few very long interviews, and this effects continues all over them (I sent one of the most prominent examples, most times it is much gentler).

I do see it in the LCD screen, but I was sure it's the AUTO LCD brightness fooling me around.

Any other thoughts? maybe it's codec related?


Thanks,
alon
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Old May 19th, 2010, 05:02 AM   #4
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Two stabs in the dark from a complete amateur

Are you using exposure simulation mode? Recent posts indicate since the firmware upgrade - this setting in Liveview overrides manual settings and is like shooting in auto. However as your scene is consistently lit there should be no reason for the aperture to change. Watching the clip on loop there is a point at about 1.4 seconds where the cupboard door on the lower left side increases in brightness.

A while ago I read about the frequency rating of light bulbs causing problems on the 5D. i dismissed it at the time as I think it was a Red owner emoting. I cannot find it now - but those results - if they are in camera - could be effected by the lighting.

Coming from a computing background I am tempted to say you've got a faulty VGA plug on your monitor. Only kidding.

With regards

Jeff
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Old May 19th, 2010, 08:28 AM   #5
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Do you have auto lighting optimizer enabled?
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Old May 19th, 2010, 11:05 AM   #6
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Thanks Jeff,
well - it's not exp. simulation ('m using movie+stills), but it might be the second thing - since I believe i never saw it in a natural lit scenes. The thing is that the interview was lit with 3200K studio lamp, that should give a consistent light, shouldn't it?

Remember where you saw these RED people comments ? ;)

(being a computer guy myself I thought it's the codec breathing. but that's too much breathing...)
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Old May 19th, 2010, 11:33 AM   #7
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With the change occurring with a slight shift or movement of the camera, seems like auto exposure change to me.

1. Was this a zoom wide open that might be on the edge of Fstop range or perhaps a sticky aperature leaf. I notice this happens to me occasionally with the two auto Canon lenses I have. Most of the time I shoot with my vintage non- auto Nikon primes with adapters, and do not see anything like this.

2. As far as exposure simulation (and I don't have my 5D in front of me) at least on earlier firmware, you could have Movie + stills selected and still be in exposure simulation. That was a subcategory of the setting process, and you had to be sure it was changed to movie too! It wasn't clear from your post that that is what you did.
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Old May 19th, 2010, 11:45 AM   #8
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Hi Chris,

Yep, I did change to movie display. as for the len - i'm using Canon 24-70 L 2.8, and no change in exposure is suppose to/or happening de facto.

alon
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Old May 19th, 2010, 03:41 PM   #9
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Now I'm really guessing here, but if you where using 3200k lights, which draw a lot of power, in a place where the power is a bit iffy or over-loaded, you might have been getting a power flux flicker from the lights that you might not have noticed since you where concentrating on so many things at once during shooting. I say take the lights out of the equation and test awhile in sunlight and see if it's still happening? But I really think the camera is compensating for exposure somehow which I believe is what you're thinking too. I don't think it's the codec because if so, we would see tons of this out there with the amount of messing around in crazy lighting environments people are trying.
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Old May 19th, 2010, 09:27 PM   #10
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I don't believe this is an exposure change because the highlights did not seem to change, nor did most of the frame. I believe this is more likely a contrast change from either a fault or some setting that effects contrast like Highlight Tone Priority or Auto Lighting Optimizer. Since Evan brought up Auto Lighting Optimizer and the question hasn't been answered, I would look there first.
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Old May 20th, 2010, 02:35 PM   #11
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Thanks.
I will try to do a test with highlight tone priority and auto-lighting off, and i'll see if it happens again...

alon
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Old May 21st, 2010, 06:16 AM   #12
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Light Flicker Discussion 50hz v. 60hz

Flickr: Discussing Flicker in 5D MkII Movie Mode Caused by Manual Lenses. in EOS Cameras and Manual Lenses

Alon I cannot find that discussion using Google. However the problem is raised again in the above thread on Flickr (no pun intended). I am not sure if there is any truth in it - I have not used my camera much indoors yet. One opinion (if you can go by this) is that Flourescent lighting may cause the problem.

The Auto Lighting setting I guess is there to control it.

With regards

Jeff
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Old May 23rd, 2010, 06:55 PM   #13
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I haven't personally tried ALO on video, but it basically seems intended to dynamically shift the gamma in order to improve shadow detail. If it's doing that on the fly I would expect it to produce exactly the type of thing we see in your video.
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Old May 25th, 2010, 10:44 AM   #14
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The new firmware 2.07 looks like it addresses this issue:

http://www.dvinfo.net/forum/canon-eo...2-0-7-out.html
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Old May 25th, 2010, 12:40 PM   #15
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wow! i'll update the firmware also. it's so good to discover an issue which is real and not human related ;)

For some reasons the shift is mostly noticeable in low light situations (exterior with lot's of light doesn't seem to be that affected). anyhow, hope the firmware will make the problem go away.

Thanks all.
alon
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