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Old January 12th, 2007, 12:42 PM   #1
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removing green 'dead pixel' type dots from footage

Hi,

I think I have a problem with my canon xl1 and I have 2 green dots on some quite dark footage. They show up big time and I'm wondering if there is any way of removing them. I have tried making the footage black and white and it is still obvious.

I do not have a clue what to do.
Many thanks
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Old January 12th, 2007, 12:54 PM   #2
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How long is the clip? Could you try to blend them into the dark image with After Effects? Is the shot "locked down"?
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Old January 12th, 2007, 01:03 PM   #3
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Quote:
Originally Posted by Mike Horrigan
How long is the clip? Could you try to blend them into the dark image with After Effects? Is the shot "locked down"?
Mike,
The shot is on a tripod but zooming and panning all over the place. If it was a still image it would be easy to do, or if the movement was through keyframing and not me moving the camera.. but i cant see a way round this
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Old January 12th, 2007, 01:22 PM   #4
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Hi David,

I'm new to this but it seems to me that you have a big problem on your hands. Other than going through frame by frame I can't think of an easy way to fix this.

I'm sure that one of the experts who come on here from time to time will be more helpful. If there was a way to "track" the two dots and have them altered automatically? Probably impossible.

Sorry, I'm not much help on this one.

Mike
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Old January 12th, 2007, 01:31 PM   #5
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well thanks for yoru suggestion mike its a good idea but I cant see a way of doing it. I could possibly create a file in photoshop that is clear except for the 2 dots in the relevant place but I will still have to keyframe them frame by frame. All in all there is about 2 mins of footage so would be a pain...

It seems like there are so many pieces of software to correct this for photo but not for video
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Old January 12th, 2007, 01:35 PM   #6
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what am i talking about?!

The green dots arent actually moving on the screen so I can easily cover them up with a darker colour.. certainly a good short term fix but does anyone know of software for hot pixel removal?
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Old January 12th, 2007, 01:39 PM   #7
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Awesome! If they are not moving... then that's an easy "rough" fix!

What about exporting the two minutes as individual frames? Maybe Photoshop can do something to each individual frame and you can import them all back in.

This is all just theory. I don't have any experience with Photoshop.
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Old January 12th, 2007, 02:01 PM   #8
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Create a track matte from the defective pixels in photo shop. ( grab a frame of the darkest so you can see the pixels, in photo shop make the rest of image black, pixels white, invert to create black matte. You willl have to magnify a lot to get accuracy in creating this matte). Use this with another copy of the clip but use motion to move clip just a little so with the track matte it covers those pixels on your main clip. That is you will look through these defective pixels to the same clip moved just a little so that there is clip content rather than defective pixels. You may have to change which way you move this clip at times to get best results. Once had to do this over a two hour shoot!!!

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Old January 13th, 2007, 04:34 AM   #9
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Hi David,
If the pixels are not moving maybe a good solution would be to open the footage in AE. Then make two layers with the same footage. Zoom on the top layer and make a substract mask on the pixels you want to get rid. If the areas take only one pixel you even dont need to feather. Then simply shift the bottom layer the same ammount of pixels as the defect. The result is that you will have that green pixels changed to the neiborhood pixel color giving a natural correction. May be you will have a few frames where you anyway will see the pixels (for example when the pixel go from a very dark to clear colour or viceversa) in that case you can keyframe those frames and move your back layer some extra pixels.
Also you can try to key out the pixels instead of masking (that should work even with movin pixels)
Only an idea.
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Old January 13th, 2007, 04:45 AM   #10
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Ron and Martin, many thanks for your suggestions they are much appreciated. I pain stakingly created a plain black pixel to go over the 2 problematic ones yesterday but found I had to occasionally put in a brown, white or red pixel so it took a while.

Martin, I am not massively familiar with AE but I will certainly give that a try as some sort pixel replication of the neighbouring pixel is exactly what I am after.

I will report back with my results (and probably some more questions.)

Thanks to everyone for their help so far.
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Old January 13th, 2007, 11:08 AM   #11
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Ron has it right. If you cover each bad pixel with the pixel to the right or left of it, it is less likely to be noticed.
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Old January 13th, 2007, 12:01 PM   #12
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Yes for panning motion use pixels from above or below, for tilting motion of camera use pixels from either side. Zooming may cause a combination of these effects hence my comments that the clip used with the travelling matte may have to be adjusted for camera motion. For the two hour video I corrected I mainly used pixels from below the defects ( move second overlay clip from behind matte, up a couple of pixels). On the few occations where I had zoomed in over some coloured boundaries used the pixels from the side. I had made the matte just a little bigger than the defective pixels too.

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Old January 14th, 2007, 12:54 PM   #13
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Just moved to the XL-H1 because of a blown pixel in my XL-1. The way I fixed the last couple of clips taken with the bad pixel was to duplicate the track, crop it to a couple of pixels larger than the bad one, apply noise reduction, and overlay. Worked great. You really don't notice the slight blur on a 4 or 5 pixel overlay.
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Old January 14th, 2007, 02:34 PM   #14
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You could try RE:Fill

http://www.revisionfx.com/rfil.htm
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