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Sudden colour shift in footage

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Kenneth Scicluna
Sudden colour shift in footage
on Sep 29, 2011 at 9:12:37 am

We have an EOS 7D. On some shots we're finding that colour temperature shifts -- it's a slight shift, but it renders the shot useless.

Shots taken on a manual setting, fixed white balance and with a fixed focal length.

The issue can be observed on the "raw" H.264 clips right off the CF card.

Does not happen on all shots (thankfully) but on random few.

Any ideas?


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Bob Dix
Re: Sudden colour shift in footage
on Sep 29, 2011 at 9:25:51 pm

In my experience with a 5D mark II this may happen sometimes if you do not get the exposure correct or the camera is slow adjusting between shots, a shift in exposure although slight will effect the color. If you shoot in RAW only this can be fixed in Canon Digital Professional & but, perhaps not Adobe Photoshop.Do not shoot in JPEG.

Check the LCD for obvious over exposure of any shot, and re shoot.

Most digital cameras tend to over-expose, I suggest you alter the adjustment to -1, this will reduce that (in the highlights) except for average ambient light.

We use two of these cameras and have never lost a good shot in 3.5 years.

Good luck
Ps I understand it is a 7D (it may not operate the same as the 5D and you say you shoot in RAW H.264) but, that is the movie codec H.264 mov not stills. Unless I stand corrected ? Or your problem may be a slow CF card ? Just a thought.

Freelance Imaging & Video
AUSTRALIA


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Bob Dix
Re: Sudden colour shift in footage
on Sep 29, 2011 at 10:13:02 pm

In my experience with a 5D mark II this may happen sometimes if you do not get the exposure correct or the camera is slow adjusting between shots, a shift in exposure although slight will effect the color. If you shoot in RAW only this can be fixed in Canon Digital Professional & but, perhaps not Adobe Photoshop.Do not shoot in JPEG.

Check the LCD for obvious over exposure of any shot, and re shoot.

Most digital cameras tend to over-expose, I suggest you alter the adjustment to -1, this will reduce that (in the highlights) except for average ambient light.

We use two of these cameras and have never lost a good shot in 3.5 years.

Good luck
Ps I understand it is a 7D (it may not operate the same as the 5D and you say you shoot in RAW H.264) but, that is the movie codec H.264 mov not stills. Unless I stand corrected ? Also, if you use live view you may get average exposure as for video ( as that is how it operates, not as I presume you have set it as evaluative. The Canon manual states that the exposure for video is not the same as for stills, and you cannot change that.

Freelance Imaging & Video
AUSTRALIA


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Kenneth Scicluna
Re: Sudden colour shift in footage
on Sep 30, 2011 at 4:47:33 am

Hi Bob

thanks for your input. What I meant, re raw, and that's why i put it in quotes, is that the effect can be seen on movie files that came off the camera, ergo pre processing by any software.

Also, as mentioned, the camera is locked down, fully manual, with no in-camera shot adjustment. Therefore there should be no reason for the camera to tweak whatever's coming in. And that's what's so annoying about this glitch: it's a sudden shift, from one frame to the next.

We suspect the camera may be on its way out -- but we were curious to see if anyone else has ever experienced the same thing.

k


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Bob Dix
Re: Sudden colour shift in footage
on Sep 30, 2011 at 6:28:57 am

Hi Ken,

I am surprised you can see it on the LCD, if that is what you mean. The video is running at 25 fps PAL and to me you could only pick that up frame by frame in an editing suite or on 35mm film by hand, I find it difficult to understand that one frame would make any shift ??????????

Freelance Imaging & Video
AUSTRALIA

Why do you need to take one frame off a clip, which you can do of course. I still say you can fix that in Canon Digital Professional ? I go back to my days in 35mm movie film and there is a difference all be it slight from frame to frame. Maybe I do not understand what you are trying to do ?

If you mean shifts in clips of movie shots say, five seconds to the next five second clip, then the ambient light may change the color temperature and the human eye will not notice it , but, the camera will.

My son using a 5D Mark II accidentally moved the AWB setting just a fraction and set an indoor setting more than slightly green under fluorescent lights the 5D would have corrected it, set on neutral AWB.


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Kenneth Scicluna
Re: Sudden colour shift in footage
on Sep 30, 2011 at 8:00:59 pm

Hi Bob

thanks again for your kind reply.

The issue is not with one frame, but with a sudden change from one frame to the next.

The problem has manifested itself both in controlled lighting conditions and also outdoors.

I've a feeling it's an internal fault more than anything else -- we're not talking about a gradual change (the way a camera would in response to changing light levels or colour) but rather a sudden, inexplicable shift.

k


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Bob Dix
Re: Sudden colour shift in footage
on Sep 30, 2011 at 8:48:21 pm

You may have to send the 7D back to Canon Technical Service ?

Freelance Imaging & Video
AUSTRALIA


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