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Chromakey and subject lighting

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Stuart Ireson
Chromakey and subject lighting
on May 17, 2010 at 3:22:59 pm

Hi There, i'm planning my first venture into chromakey.

I think im going to use the Datavideo CKL-100 Chroma Keyer Kit for the chroma key aspect as its very cheap to hire and seems very practical

The footage once keyed out will be filtered with the red giant 'Toon-it' plug in for AE which makes a cartoon effect to the footage.

Im a little shaky about lighting the foreground. it a commission and ive no budget to practice.

how important really is a backlight? does it actually assist in the chromkey process - i mean separating the foreground subject from the green? i ask this because with the cartoon filter (toon IT)- the back light actually doesn't help the cartoon look. it makes the hair look more messy once filtered.

the overall look does not exactly require normal three point lighting... its needs to be softy evenly lit from both sides of the subject. in fact some flatness is what im going for.

my plan was to light the subject very evenly with two soft-top lights more or less equidistant and angled and 45 degrees each side - perhaps some slight variations in position to add subtle changes in modeling but nothing dramatic.

perhaps im completely barking up the wrong tree, could anytone tell me if they think this is ok or if im missing something?

# 105w (420w equiv) softop lights were what i was guessing might be appropriate for the subject. they are daylight balanced but with the dramatic cartoon filtering and final graphic look im not sure how much that matters.

many thanks for any light shed.

Stuart


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Mark Suszko
Re: Chromakey and subject lighting
on May 17, 2010 at 4:01:58 pm

In this case, the only reason for backlight is to use a magenta-gelled back light to suppress green spill from the green wall to improve the chromakey. And if you keep a decent distance from the wall, and light the green evenly but not blindingly hot, you shouldn't need that. Since the goal eventually is a cartoony look, the flat lighting seems like it would be a good choice here.

I'm guessing your replacement backdrop in the keyer will be a flat white or very light gray, or black. That will give the toon shader an easier time of it, I should think. It would be neat to see some stills as you put this together. A really convincing cartoon-look without a lot of touch-up roto-paint is sort of a holy grail kind of thing. I hear good things about the Red giant plug-in, would like to see a real-world test of it.


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Stuart Ireson
Re: Chromakey and subject lighting
on May 17, 2010 at 4:43:05 pm

thanks, Marc that helps with the back light alot!

the kit im gonna use is actually one of those led light rings with the glass bead screen. it sounds great. but we will see when it comes to the day...

I've already tested TOONIT alot on pre-matted green screen stock for practice. im happy enough with the result - no, it certain ally wont look anything like a scanner darkly, but for me it works well when the effect applied is subtle. ive attached some rough pics of the practice...





im just applying toon IT to the video footage, inserted backgrounds are drawn by hand on photoshop.

Stuart x


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Mark Suszko
Re: Chromakey and subject lighting
on May 17, 2010 at 9:21:49 pm

If you are using the chromaflex type setup for chromakeying, then the screen needs nothing except the LED illuminator on your lens. Any other light hitting the retro-reflective cloth can only hurt.

Use backlight on the actor only if it will match the lighting in the new virtual environment you create. I.E. if the sun in the cartoon is from the left at 45 degrees, light your actor at the same angles to match. Shadows that don't match angles and seem to not be motivated are one of the easiest giveaways to a bad comp.


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Mark Suszko
Re: Chromakey and subject lighting
on May 17, 2010 at 9:27:40 pm

BTW the samples look very nice to me. I found the bigger trick with this look is the temporal artifacting: it seems to help to reduce the number of frames per second to cut down on flicker of details and better imitate shooting stills "on twos", as they say. The stills using these toys ALWAYS look good; it is not until you try to make them MOVE that the illusion breaks down and all the real hand-drawn animators have their laugh at your expense.

And keep reducing detail, is my last suggestion. You might want to experiment with deliberately shooting some footage over-exposed to blow out small details of the image before the plug-in ever sees it. Or you can try the color-corrector to do that artificially to existing footage at a stage *before* you apply the toon shader. That's just what I think based on my own experiments with this kind of thing. Your mileage may vary.

Best of luck; show more stills and motion samples when you can!



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Stuart Ireson
Re: Chromakey and subject lighting
on May 17, 2010 at 10:16:31 pm

I really appreciate your input Mark. im much clearer about the backlight now. and your advice on reducing frames per sec is something i hadn't thought of - so thanks for that. also i see how perhaps overexposing a i bit may help... ill have to play around as much as i can for the first few hours of the shoot. luckily for this commission - they're not expecting too much, im sure it will exceed their expections even if it has its flaws. for my own projects later in the year i'll prolly have a clearer idea what im doing.

Thanks a million

Stuart


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