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Old March 3rd, 2006, 11:45 AM   #1
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Color correction issue

I'm currently editing a short film for a friend (shot with an XL2) and I ran into a color problem. She used by mistake the tungsten WB preset to shoot some scenes with daylight lighting. As a result, everything is blue.

Now, I've corrected this before, it's usually not that big a deal, except in this case, there is also some white clipping which has introduced an unusual problem I had never seen before. Just barely at the IRE limit, before the whites clip, it creates a kind of solid turquoise color. I have tried for hours, I can't get rid of this very weird color artifact.

I'm using Premiere Pro 2.0, which has some decent color correction tools, but this turquoise cast has just been impossible to correct so far. Even if I choose the secondary color correcting tools to specifically try to work on that very color only, I can't seem to grab that color with the color pipe to then alter it properly. It's like the NLE doesn't see the turquoise color cast at all. This color has a life of its own.

Follow this link to better see the effect I'm talking about. Notice where the whites clip in the windows, there is a turquoise cast in between the blown whites and the regular blue cast (which is easily correctable).

BTW, for anyone wondering what is outside the windows, it's tree branches with snow on it.

I figured I was better off posting this in the general DV editing forum since I assume (maybe wrongfully) that this a DV problem, not necessarily NLE related, and therefore that the solution might not be NLE dependant.

Thanks for any help.
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Old March 3rd, 2006, 03:58 PM   #2
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I tried messing around with that JPG in Paint Shop Pro, and I don't see a way to get rid of the turquoise in the tree branches, without separating the foreground from the background, to manipulate color in fore/back separately. I don't know of any practical method to do that with any sizable length of video.
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Old March 3rd, 2006, 04:10 PM   #3
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I just played with the image some more, and somehow managed to get the branches to a green without the woman's facial coloration being totally horked. If you shoot me an email, I can send you back the image I wound up with, if that might help.
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Old March 3rd, 2006, 04:20 PM   #4
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I put it up on the net:

http://members.aol.com/robertmwright...eriment001.jpg

It's real rough, but is this getting closer to what you are looking for?
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Old March 3rd, 2006, 04:54 PM   #5
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Hey Robert thanks for your help. See the thing about that turquoise color is that it should actually be white, or near white, light grey, as it's snow. I know that it looks like the turquoise is part of the branches but it's not, it is (or should be) near white. I have other shots where it's clearly the snow (or anything else white) that becomes this strange color. It becomes like this just before the whites clip and after it is poperly exposed (so to speak). It is an in between and has no relation to any other color in the shot.

As you probably noticed, it is possible to fairly easily correct the face, branches and anything else properly exposed in the shot but that turquoise color never goes away. You can change its hue slightly, you can dessaturate it a bit, but never have I been able to get it back to its original white or near white color (that is while leaving the other colors unchanged).

I don't know, maybe it's hopeless, I was just assuming there was something I wasn't aware of that would allow me to correct it fairly easily. I could probably correct each frame at a time of course, but that's not happening.
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Old March 3rd, 2006, 05:00 PM   #6
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In my opinion, the original image looks kind of nice. But it may make sense to make the colors more normal, which is possible.

Here's a quick whack at it in Photoshop:
http://www.glennchan.info/Proofs/dvi.../corrected.jpg

If you have After Effects, it can do the same thing as Photoshop.

If you wanted, you could also isolate the foreground via rotoscoping in something like Photoshop or After Effects. If you only want to get rid of the turquoise/cyan, that shouldn't be necessary though.

My example would likely look better with more of the original cyan in there. Just adjust the adjustment slider in Photoshop.

Original PSD:
http://www.glennchan.info/Proofs/dvi.../corrected.psd
in the top adjustment layer, look in the dropdown menu under master for cyans.

I hope that helps.
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Old March 3rd, 2006, 05:42 PM   #7
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I don't use Premiere, but it's pretty easy to isolate the turquoise with Photoshop's secondary color corrector (i.e., Hue/Saturation): http://img364.imageshack.us/my.php?i...touched6yw.jpg

Could you use the cast as a stylistic element or convert the segment to B&W?
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Old March 3rd, 2006, 05:47 PM   #8
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Emre - Out of curiosity, I'd love to see that image at full res. Looks like you got the branches a lot better than I did. How did you desaturate the color in the branches without losing the color in the woman's face?
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Old March 3rd, 2006, 05:56 PM   #9
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Glen got the branches looking reasonably realistic (I don't know if it looks like the genuine scene, since none of us are able to see that, but it looks "realistic" at least). If you can get the branches to where Glen got them, at the same time as getting the face to where I got that, you should be able to tweak it to look pretty dang good, I would think.
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Old March 3rd, 2006, 06:23 PM   #10
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Hey everybody, thanks for all the replies.

Emre so far I haven't talked it over with the girl that brought me the footage but leaving it as is would probably look weird, especially that it is meant to be cut with some outside shots which were correctly white balanced. But I guess I could talk her into playing with tints and tones to stylize the image and go with the flow instead of against, so to speak.

Robert you're right, Glenn and Emre both got the outside background to look nice and realistic enough, I'm just not sure how to automate such a process in PPro without going over each individual frame.

I know I can get rid of the turquoise by doing a frame by frame correction, but that's not happening any time soon. I've got a lot of that footage and it was all handheld (with auto exposure on top of that). That would be a nightmare of titanic scale requiring an insane amount of time.

I don't have After Effects, just Premiere Pro 2.0.

The weird thing is that there is now a secondary color correction tool in this new version of PPro which should allow me to just select that turquoise color and play with it independently just like I would in Photoshop, but like I said in my original post, it's like the NLE doesn't let me change that specific color, like if it wasn't recognized.

I click on the turquoise color with the color pipe but when I look at the B&W mask, none of it has changed. It's awfully weird and I don't know if this makes any sense (nor how to explain it), I guess I'm going to play with it a bit more, but so far everything I've tried in Premiere to remove the turquoise color has failed.
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Old March 3rd, 2006, 06:42 PM   #11
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I don't know how much footage you need to fix, but you could export the frames as a series of stills and write a script to batch process them with Paint Shop Pro or maybe Photoshop (I don't know Photoshop, but I know it can be done in Paint Shop Pro) and then convert the stills back to video. I don't know Premiere at all, so I don't know how well it handles exporting to and importing from a series of stills, but if nothing else, VirtualDub can do it pretty easily.
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Old March 3rd, 2006, 06:48 PM   #12
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Here are some more frame grabs:

frame grab of what the trees and snow should look like had the inside shots been properly white balanced

frame grab of what has worked best so far for me (tinting the image a bit and changing the overall hue)

Here's a shot though where that doesn't work so well:

original

modified

That remaining greenish cast is ugly any way you slice it.
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Old March 3rd, 2006, 06:50 PM   #13
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Robert, as long as the process can be automated that's fine by me. I just don't want to do it one frame at a time. I work with Photoshop myself. I'll look into your suggestion maybe it can be done.

To be continued...
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Old March 3rd, 2006, 07:19 PM   #14
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If you can't do scripts on batches of images in Photoshop, I could probably find the install program for Paint Shop Pro 8 trial version. It's good for 30 days, with no limitations on functionality. I've used the scripts, and it's not all that hard to do, but I've only done it a few times, so it still takes me more time to figure out how to get the script written correctly, than figuring out what I want done (I've used PSP quite a bit over the years, but seldom scripts). One thing I like about PSP is the "one step photo fix" tool. It's pretty decent for a quick and dirty fix-up and I do use it to touch up photos for friends super fast on occasion.
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Old March 3rd, 2006, 08:50 PM   #15
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Photoshop can do batch actions onto a still image seuqence.

There might be some way in PPro to do the same thing as Photoshop. maybe try:
Do levels first... drop down the gain on red to about 45% ish.
Then try the secondary color correction (didn't know that PPro has it now). Don't drop saturation down all the way. Also , do increase luma or brightness.

Another whack at the image:
http://www.glennchan.info/Proofs/dvi...corrected2.jpg

2- Another good option is to make the image black and whie and push it very stylized.
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