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key light grainy key..?

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melissa kernkey light grainy key..?
by on Mar 26, 2008 at 7:23:46 pm

hello, my key is really "grainy" pixelated looking..I shot people on green screen and they look really good, but when the footage plays after applying keylight and making a quicktime- its all grainy..any ideas??



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Shad FromanRe: key light grainy key..?
by on Mar 26, 2008 at 9:37:08 pm

In looking at old posts concerning this issue, since I'm having similar issues with keylight, Dave LaRonde appeared to have a good formula for this issue. But when I look to see his advice, there is nothing there. It just says apply 2 keylights, though it looked like he had a more detailed. If you're out there Dave, can you help us out? Your method seemed to be the way to go.



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cowcowcowcowcow
Dave LaRondeRe: key light grainy key..?
by on Mar 26, 2008 at 10:43:36 pm

You say you've looked at the Keylight Status viewer, and you're convinced the key ought to work? The Status view shows white all over the subject and gray at the edges?

You've got a good key. The only problem: it looks like a certain disgusting, stinky brown substance. Here's what I do:

• Duplicate the keyed footage, and turn off the upper layer.
• Fool with the lower layer's Keylight settings until it looks like the subject looks fine, but is over a grayish, washed-out chroma key background. It'll take some doing, but you will have gotten it to the point where Keylight's spill suppressor is working. That's good, because the Keylight spill suppressor works darned well.
• Open the Modes panel, and use the upper layer as an Alpha Matte for the lower layer. For more info, look up Track Mattes in AE Help.

Poof! You're done! You have a clean key, AND you have spill suppression.

So why does this happen? Your chroma key background's level is probably too high for Keylight. Keylight likes less light on the background than other keyers. The usual admonitions about even lighting and the distance of the subject from the background apply.

Access to a waveform monitor can be a GREAT help. If the brightest highlights on the subject come in at 100 IRE units, the background should be about 45-50 IRE units. The waveform of the green screen should be a thin, level line at 45-50: the thinness of the line indicates even lighting top to bottom, and a level line indicates even lighting side to side.

You can accomplish the same thing by measuring footcandles with an incident light meter. Even though it's much more time-consuming, it can really help when the time comes to key.

Now, if this footage is DV, your fun is just beginning. The color resolution (aka color sampling) of DV video is about as bad as it gets. Oh, it's good enough to fool the human eye, but computers are a LOT more discriminating, and DV's stinky color resolution poses real challenges for chroma keying.

If you've never tried keying DV video before, I recommend watching a podcast by Alex Lindsay, the founder of DV Garage and Pixel Corps, called "The Road to 1080p Part 2". In it you will find an excellent description of the differences between 4-4-4, 4-2-2 and 4-1-1 color resolution, and you will come to understand the challenges of keying DV. It's WELL worth the 15 minutes it takes to watch.

You can get the podcast here: http://macbreak.libsyn.com/index.php?post_id=70596

As you watch if, keep in mind that Alex Lindsay runs a company that makes DV chroma keying plugins... and he STILL doesn't recommend trying to chroma key DV.

Dave LaRonde
Sr. Promotion Producer
KCRG-TV


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melissa kernRe: key light grainy key..?
by on Mar 27, 2008 at 6:41:47 pm

hey, thanks..I would of never thought of that process and it works beautifully. cool cool



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danny haysRe: key light grainy key..?
by on Jan 8, 2009 at 3:11:12 am

Adobe Ultra 2 will key DV great. Danny Hays



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julian nelsonRe: key light grainy key..?
by on May 27, 2010 at 4:00:14 pm

amazing, i was having trouble with the edges of my subject but i did what you suggested and it worked great. i also put the replace method to hard colour and it worked a treat


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Garrett RobinsonRe: key light grainy key..?
by on Jun 23, 2010 at 10:49:44 pm

This is really great - extremely helpful. However, I'm not sure I've totally got what you're saying right as regards the lower layer and the effect to achieve there. Basically I'm still getting some green "bleed" on the edges of my subject and your explanation sounds like that shouldn't be there. Do you have this posted anywhere in greater detail? Maybe a walkthrough somewhere?


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Alex ElkinsRe: key light grainy key..?
by on Sep 15, 2010 at 12:45:52 pm

David, I just discovered this post and although it's over two years old was still completely relevant and an incredible help. Just wanted to say thanks for sharing such a useful tip.

Alex Elkins

Salad Daze Films - Freshly Tossed
Check out my latest addition to the Creative Cow Reels Section


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Max JacksonRe: key light grainy key..?
by on Oct 20, 2010 at 7:04:55 am

+1

I just read this brilliant post and can see it working while I write it down in my notebook. Just sublime, brilliant and so simple.

The spill suppression bonus is just darn good stuff too.


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Kurt BergeronRe: key light grainy key..?
by on Dec 28, 2010 at 6:01:10 pm

O.K., I'm gonna put myself out there and look like the fool. I love the way this post SOUNDS, but I still need some help. I'm relatively new to green screen. We don't have the BEST light kit in the world, a couple soft boxes and a couple brolly boxes, but it's been getting us by, at least for web/youtube videos where are videos are primarily based. The blacks have a graininess to them that I smooth out as best I can, and additional smoothing is added naturally when exporting in H.264 and uploading to youtube, they look fine. I'm having some issues at the moment however and I would love to give this post a try and the simple "just get it till it looks gray" is still a little vague for my experience level. What should I be playing with? can we break this down a little more? Thank you SO much!


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Brendon MurphyRe: key light grainy key..?
by on Mar 3, 2011 at 3:53:26 pm

Great Keylight tip - thanks!


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stig olsenRe: key light grainy key..?
by on May 6, 2011 at 10:01:32 am

Can someone please explain what this means:

"Fool with the lower layer's Keylight settings until it looks like the subject looks fine, but is over a grayish, washed-out chroma key background. It'll take some doing, but you will have gotten it to the point where Keylight's spill suppressor is working. That's good, because the Keylight spill suppressor works darned well."

I guess the layer that is keyed out is made as good as possible before it is duplicated and already looks as fine as I can get it...
Thats why I do not understand what exactly I need to do with the layer underneath.


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Ed RomeroRe: key light grainy key..?
by on May 12, 2011 at 5:02:46 pm

can anyone elaborate on this?

"Fool with the lower layer's Keylight settings until it looks like the subject looks fine, but is over a grayish, washed-out chroma key background. It'll take some doing, but you will have gotten it to the point where Keylight's spill suppressor is working. That's good, because the Keylight spill suppressor works darned well."

Thanks.


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mateus machadoRe: key light grainy key..?
by on Aug 8, 2012 at 3:19:21 pm

Hi Dave,

I have some doubts on what you wrote: "• Duplicate the keyed footage, and turn off the upper layer.
• Fool with the lower layer's Keylight settings until it looks like the subject looks fine, but is over a grayish, washed-out chroma key background."

First, in wich view mode should the layers be duplicated? satus? and wich settings should I fool around with? on the screen mate settings?

thank you,


Mateus


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Craig RickerRe: key light grainy key..?
by on Aug 20, 2012 at 12:59:31 am

+1 on this


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Josh LaVilleRe: key light grainy key..?
by on Sep 7, 2013 at 12:43:35 am

I just used this tip (still relevant!) and thought it needed some clarification. First, get a good key with Keylight according to the screen matte view (see another tutorial if you need to).

Then, duplicate the keyed layer. Turn off the upper layer, go into the lower layer's Keylight effect.

This is were people are getting confused. Just use Keylight on this layer to eliminate spilled color, not to do any keying. I have gotten great results just by reseting Keylight, and then selecting the color to key as the hottest part of my green screen. What you want to avoid are artifacts/noise in the dark grays.

Now, on the modes switch of the lower layer (you just color suppressed), choose to use the upper layer as the alpha track matte.

Voila! No more funky edges and much fewer grainy artifacts.


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