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uwxplorer

Red out of nothing (actually out of blue or green) in FCE?

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Still experimenting with my CX550V and MWB...

SoCal water can be VERY green. I think I am going to show it as it is. But that also means it absorbs light a lot. Recently, I took a look at my slate on which I had painted red stripes: I could only see black stripes (with my eyes) and I was maybe only 30 feet deep. On the other hand, video lights reach only so far. Therefore there are shots where all red is gone. Color correcting in this case is useless: there is absolutely no information in the red plane of the RGB decomposition.

I am wondering, and this is my question, whether it is possible in FCE to take information from one of the other planes (say the green one) and after having chroma keyed it in order to isolate a specific area (say, a fish), artificially "paint" this area in red. In other words, define this area with the corresponding information about the green plane as being now the information for the red plane for that area as well.

To illustrate it with a theoretical example, suppose I have a gray fish in a blue-green water environment, but my camera does not collect any red. The movie will look blue-green just as the fish will. In principle, if I could "cut-out" the fish in the green plane and paste the pixel values of this region of the green plane into the red plane, I could recover a gray fish (rather than a blue-green fish).

Thanks for your comments or pointers.

X.

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Still experimenting with my CX550V and MWB...

SoCal water can be VERY green. I think I am going to show it as it is. But that also means it absorbs light a lot. Recently, I took a look at my slate on which I had painted red stripes: I could only see black stripes (with my eyes) and I was maybe only 30 feet deep. On the other hand, video lights reach only so far. Therefore there are shots where all red is gone. Color correcting in this case is useless: there is absolutely no information in the red plane of the RGB decomposition.

I am wondering, and this is my question, whether it is possible in FCE to take information from one of the other planes (say the green one) and after having chroma keyed it in order to isolate a specific area (say, a fish), artificially "paint" this area in red. In other words, define this area with the corresponding information about the green plane as being now the information for the red plane for that area as well.

To illustrate it with a theoretical example, suppose I have a gray fish in a blue-green water environment, but my camera does not collect any red. The movie will look blue-green just as the fish will. In principle, if I could "cut-out" the fish in the green plane and paste the pixel values of this region of the green plane into the red plane, I could recover a gray fish (rather than a blue-green fish).

Thanks for your comments or pointers.

X.

 

have a go with the 'channel mixer' effect in the channel effects. what it does is to allow you to remap channels... in your case remap the green or blue channel to the red channel. the green channel will always have less noise/artifacts, so it good to start with that, and only add the blue channel if you need too.

 

it's a very powerful tool, and can be used to put a lot of color 'back' into the image. there probably wont even be a need to do the chromakey/rotoscoping that you mentioned.

 

however if you think, cool i can remap the green channel to the red channel and the blue channel to get a much better quality image, you'll end up with a black and white image lol

Edited by Huw Jenkins

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thanks for the suggestion. I got similar pointers from the FCE forum at Apple but that won't work. It is like hoping that some of the objects I wanted to add a red touch to would by a miracle be highlighted in another channel (to the exception of all other objects), but that is not the case.

For whatever reason, the red channel of the sequence I was interested to edit is absolutely empty (I probably was using AWB at the time). This probably explains why the CX550V just blows out the reds when using MWB in these circumstances: it simply does not see ANY red at all, so everything becomes red. I can't blame the camcorder though, just the green SoCal water. Before my last trip last week-end, I drew red stripes on my slate. I tried to MWB of this slate once but gave up, as I could not even see the color of the stripes by eye. I was maybe 30-40 ft deep...

The B&W effect might be the only way to salvage that clip. But I most likely will just give up on it.

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Yes it is possible to chroma key a subject with color correction, use the same clip as background to your keyed subject and single out a subject for "correct coloring" keying, all in FCE. However The amount of work to do that isn't light and the look will be weird.

 

For future shooting, use lights and/or a filter and also MWB frequently as you descend. If you don't want to use MWB, keep it in daylight setting. You'll find that there is a bit red channel even at 30ft if you don't mess with WB.

 

http://wetpixel.com/forums/index.php?showtopic=23629

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If you have After Effects CS5 you can rotobrush your subject out and put it in a new, more palatable background.

Steve

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It's a moving subject, so any approach would require far more effort than the clip is worth (plus I don't have After Effect!)...

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In the past, rotoscoping anything had to be done frame by frame and would take many hours/days/weeks to accomplish. The AE rotobrush tool is designed to roto out moving subjects. Here is my tutorial. http://www.kenstone.net/fcp_homepage/rotob...s5_douglas.html

Steve

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The Rotobrush in AEFX struggles on low contrast subjects, like underwater clips where there's a strong color cast. It needs chroma and luma contrast to work well.

It's a nice progression from Commotion Pro and for scenes with clear contrast, it is very useful. However for underwater clips, the effectiveness is limited and it can be confused in busy scenes. As the Adobe marketing machine usually only touts the positives and not the negatives, I think it's safe to say that for underwater use, I'd test the tool vigorously before shelling out the money on the software.

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Hey Drew,

Look at the horrible frame of the manta in the article. Can't get much lower contrast than that and it still worked great. Haven't yet used it much but I was pretty impressed with it when I did the article.

Steve

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unfortunately, when it comes to rotoscoping/keying unless the new background's lighting and angle match perfectly, it'll never look real, let alone the light dappling effect created by shooting underwter. i think even if you use the same background, but change the color of foreground, unless you lightwrap it really well, it's gonna stand out like one of those pictures you get from a photo booth with you and tom cruise / kylie minogue. lol

 

however if you want to go the leandro blanco route, then this is probably your best bet for easy keying.

Edited by Huw Jenkins

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