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Color distortion when filming

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Caprice View Drop Down
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Post Options Post Options   Quote Caprice Quote  Post ReplyReply Direct Link To This Post Topic: Color distortion when filming
    Posted: 16 June 2019 at 01:19
Hi,
Does anyone know what has caused the following effect?

I have been filming for a number of years and have filmed in this venue before and have never seen this color issue before.

I'm filming on an A7Rii at 100fps with a CZ 35mm manual focus prime. The audio is a Sony blue-tooth unit.

When we finished the interview, I then went on to film the B roll footage straight after with the same settings in the same location and the footage does not have the effect going through it.

Anyone have any ideas?
Ross by Greg Forster, on Flickr]Ross by Greg Forster, on Flickr[/URL]
 



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Caprice View Drop Down
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Post Options Post Options   Quote Caprice Quote  Post ReplyReply Direct Link To This Post Posted: 16 June 2019 at 01:20
It should be playing or clicking through to Flickr. Le me know if it's not working.
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Miranda F View Drop Down
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Post Options Post Options   Quote Miranda F Quote  Post ReplyReply Direct Link To This Post Posted: 16 June 2019 at 07:01
The first doesn't play for me (missing page on server). The second does, but I can't see any colour effects on it. What am I looking for?

Okay, I can get the first one up by clicking on 'Ross'. I can see the skin tones fading in and out (was that what you meant?), but they seem to me to be doing that equally on both videos. Can you explain further?

As to possible causes, the only one I can think of is AWB, if you have that set. Simplistically put, Sony AWB looks for the colour of the brightest bits of the picture and assumes these are white, whereas the human eye kind of AC-couples each of the colour channels individually, so they will not correlate exactly under all circumstances.

On the video I see you have some saturated highlights on the car bonnet which is highly reflective. This might be affecting the AWB operation as you make minute movements while filming.

Alternatively (and more probably), there are two white lights in the shot and both of these will be saturated. If they are compact flourescent or LED (anything with rapid response) then there will be an interference (beating) between the mains frequency and the video frame frequency, rather like the old backwards-spinning wagon-wheel effect on old western movies.
So although the light looks constant in the image, it may be varying cyclically between adjacent shots and this might (guessing here!) affect either the AWB or the actual exposure between frames. Of course the eye is much more sensitive to minute changes in skin tones than in other colours (try looking at the yellows, greens, or browns in the scene) so this is more noticable.

Anyway, just my 2p worth!

Edited by Miranda F - 16 June 2019 at 07:17
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Post Options Post Options   Quote addy landzaat Quote  Post ReplyReply Direct Link To This Post Posted: 16 June 2019 at 08:02
Were both cameras set to 100fps? (that is an uncommon FPS btw) Before you also used 100 FPS? Maybe it has something to do with the syncing of the Led lights? Just a thought.
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Caprice View Drop Down
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Post Options Post Options   Quote Caprice Quote  Post ReplyReply Direct Link To This Post Posted: 16 June 2019 at 23:43
Sorry for the confusion guys. I've never posted a vid on Dyxum before. I'm not sure what the first box is asking for: "Enter the on screen display text for the Hyperlink" I just added the link into both the first and second box so both vids are identical.

Thanks for the info Miranda. Yes, my settings are AWB and Multi-metering.
The discoloration is a brownish hue the moves across the screen in a wave. It's like a type of interference but has a random feel about it. I have filmed here before and throughout the two days this year but the effect is only on this car. I looked again at my b-roll of this car and it is happening in that two. Is the camera struggling to read the tones of the bare metal car?

Thanks Addy. I'm recording in XAVCS-HD at 100p 50M. I'm shooting at this frame rate to create smooth slo-mo when required. The issue could be LED related like when shooting in silent mode under florescent.
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Post Options Post Options   Quote Caprice Quote  Post ReplyReply Direct Link To This Post Posted: 17 June 2019 at 00:17
Check out the effect in this clip. It's longer and I've sped it up so it's more prominent. Use second clip.

ross2 by Greg Forster, on Flickr]ross2 by Greg Forster, on Flickr[/URL]
 



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Post Options Post Options   Quote stiuskr Quote  Post ReplyReply Direct Link To This Post Posted: 17 June 2019 at 02:29
Originally posted by Caprice Caprice wrote:

Check out the effect in this clip. It's longer and I've sped it up so it's more prominent. Use second clip.


Those are Private and can't be viewed.

Edited by stiuskr - 17 June 2019 at 03:41
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Caprice View Drop Down
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Post Options Post Options   Quote Caprice Quote  Post ReplyReply Direct Link To This Post Posted: 17 June 2019 at 03:26
Originally posted by stiuskr stiuskr wrote:

Originally posted by Caprice Caprice wrote:

Check out the effect in this clip. It's longer and I've sped it up so it's more prominent. Use second clip.


Those are Private and can't be viewed.

Thanks. Just made it public.

Edited by stiuskr - 17 June 2019 at 03:42
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SnowFella View Drop Down
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Post Options Post Options   Quote SnowFella Quote  Post ReplyReply Direct Link To This Post Posted: 17 June 2019 at 05:04
Could they of changed the lighting to something LED based?
Looking at the ceiling and lamps there seem to be a rolling change in brightness from the lights.
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Post Options Post Options   Quote Miranda F Quote  Post ReplyReply Direct Link To This Post Posted: 17 June 2019 at 13:41
Interference from lighting was long an issue with fluorescent lighting and is now presumably a significant issue with CF and LED lighting too. The main issues are
(1) the emission spectrum is not the same as daylight or incandescent filament, and
(2) the emissions vary in output at twice mains supply frequency (100Hz for the UK, 120Hz for the US). If you have a shutter speed near to either of these, expect some rolling change. frankly, I'm surprised the amount is as little as it appears in these videos.
Miranda F & Sensorex, Sony A58, Nex-6, Dynax 4, 5, 60, 500si/600si/700si/800si, various Sony & Minolta lenses, several Tamrons, lots of MF primes and *far* too many old film cameras . . .
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Post Options Post Options   Quote Caprice Quote  Post ReplyReply Direct Link To This Post Posted: 18 June 2019 at 06:10
Originally posted by Miranda F Miranda F wrote:

Interference from lighting was long an issue with fluorescent lighting and is now presumably a significant issue with CF and LED lighting too. The main issues are
(1) the emission spectrum is not the same as daylight or incandescent filament, and
(2) the emissions vary in output at twice mains supply frequency (100Hz for the UK, 120Hz for the US). If you have a shutter speed near to either of these, expect some rolling change. frankly, I'm surprised the amount is as little as it appears in these videos.


I think you've nailed it Miranda in regards to shutter speed. Previously I wouldn't have shot at that speed. Interesting info. Something I'll need to keep in mind in the future.
Cheers!
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Post Options Post Options   Quote Miranda F Quote  Post ReplyReply Direct Link To This Post Posted: 18 June 2019 at 08:25
Beware of sub-harmonics too. eg 25, 50Hz in the UK, 30Hz or 60Hz in the US.
Miranda F & Sensorex, Sony A58, Nex-6, Dynax 4, 5, 60, 500si/600si/700si/800si, various Sony & Minolta lenses, several Tamrons, lots of MF primes and *far* too many old film cameras . . .
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Post Options Post Options   Quote addy landzaat Quote  Post ReplyReply Direct Link To This Post Posted: 18 June 2019 at 08:56
That was why asked if the other camera and the cameras before had the same FPS. You never answered. This is what I meant by "syncing"
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Post Options Post Options   Quote rosspa29 Quote  Post ReplyReply Direct Link To This Post Posted: 18 June 2019 at 12:39
HI all
I agree on the shutter speed is suspicious, in Australia mains power is supplied at 50HZ.

Also the colour effect can be from Metal Halide lighting. As the lamps age they tend to shift in colour. Prior to LED lighting becoming popular Metal Halide was the light of choice in these types of buildings. The colour shift can also happen while the lamps are warming up. the colours can appear to role through the lamps.
Regards Ross
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