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using Keylight on chroma key suits under sunlight

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Sherwin Akbarzadeh
using Keylight on chroma key suits under sunlight
on Jan 3, 2011 at 6:14:22 am

Hi,

I'm in pre-production on a project involving chroma key suits. I want to shoot it outside and being summer in Australia it won't be cloudy. I'm very wary of the difficulty of keying under such uneven lighting and initial tests have been problematic (see below). I shot it in a park to see how green foliage interferes with keying the lime coloured suits.

Before


After


I had hoped to apply several Keylight filters to the clip with each filter targeting a different green colour range but it appears that FCP will not accept more than one active Keylight filter. Is there a way around this other than exporting and then keying again? Does Keylight in AE have the same limitation? My footage is 720p XDCAM.

I expect that most of you will tell me I'm wasting my time shooting this under direct sun, but if it's possible, I'm prepared to spend the time to make it work. When I shoot this I hope to filter the light when possible.

Any advice would be much appreciated!

-----------------------
Director / DP

http://www.lightningstruckitself.com


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Chris Wright
Re: using Keylight on chroma key suits under sunlight
on Jan 3, 2011 at 8:31:11 am

do you have access to a silkscreen on a jib or something to diffuse the light for even keying?

You'll want to get a light meter for getting 60 IRE. This is for 2 reasons.
1. green or blue saturation once turned whitish, is no longer keyable.
2. no camera can do 30 f-stops in latitude so you won't be be rotoring blown out highlights for a long time.

This means that you will not only need to diffuse the light on the actor for even lighting, but bring its brightness down so that it matches the IRE of the background.

If you don't get a light meter, there's not much point in attempting this complicated shot.

Keying green over green seems like giving yourself extra work. Can you get blue suits instead? AE supports duplicated effects though.

basic keying tips
http://generalspecialist.com/2006/10/greenscreen-and-bluescreen-checklist.a...

http://technicolorsoftware.hostzi.com/


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Sherwin Akbarzadeh
Re: using Keylight on chroma key suits under sunlight
on Jan 3, 2011 at 1:29:37 pm

Thanks a lot for your reply Chris.

Blown out highlights on the suits is a big issue and I used luma keying with partial success. As can be seen in the stills, I found the green halo reflecting off the suit difficult to remove. I hope that by filtering the light and keeping the suit under 60IRE this halo will be eliminated.

One thing I don't quite grasp is how a light meter can help me. Wouldn't setting the zebras to 60 IRE give me all the information I need?

Shooting in the park was an 'extreme situation' I wanted to test. The actual location has some shrubbery but it's not as green.

Another question: Has anyone ever chroma keyed underwater footage? I'm wondering how difficult it will be to key out lime green amongst aqua blue water.

Cheers!

-----------------------
Director / DP

http://www.lightningstruckitself.com


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Tudor "Ted" Jelescu
Re: using Keylight on chroma key suits under sunlight
on Jan 3, 2011 at 2:18:47 pm

Underwater - use red instead of green or blue- that's what a lot of studios that have an underwater setup use.
However this advice is for green chroma:
http://www.steves-digicams.com/knowledge-center/how-tos/filmmaking-tips/chr...

Tudor "Ted" Jelescu
Senior Compositor/VFX Artist


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Michael Szalapski
Re: using Keylight on chroma key suits under sunlight
on Jan 3, 2011 at 4:50:22 pm

To answer one of your initial questions After Effects does not limit you to only one instance of Keylight per layer. You can do however many you want. It also has other color keying tools and I would think you would end up using more than one. Also, if you're going to be shooting in green settings, you might consider getting red suits instead of green (as mentioned).

Also, what are you trying to accomplish by keying out a person shape? Perhaps we can come up with a better solution.

- The Great Szalam
(The 'Great' stands for 'Not So Great, in fact, Extremely Humble')

No trees were harmed in the creation of this message, but several thousand electrons were mildly inconvenienced.


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Shawn Miller
Re: using Keylight on chroma key suits under sunlight
on Jan 3, 2011 at 6:52:23 pm

I agree with others who have pointed out that green may not be the best color for this job. IMO, a combination of roto and luma keying might be more effective here. I'm not sure where to buy or rent white body suits, but it might be worth a try.

Thanks,

Shawn



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Dave LaRonde
Re: using Keylight on chroma key suits under sunlight
on Jan 3, 2011 at 7:02:33 pm

I can only think of a few reasons to use a chroma key suit at all; I'll assume you're well aware that you'll only get a person-shaped hole in your video.

The most compelling reason to use such a suit would be if the subject wearing it passes behind objects in the foreground. If that doesn't happen, I'd try shooting indoors where you have more control.

Or shooting in Queensland, where I'm told it's cloudy.

Dave LaRonde
Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA


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Sherwin Akbarzadeh
Re: using Keylight on chroma key suits under sunlight
on Jan 4, 2011 at 12:17:23 am

Thanks for the responses! I'd be prepared to buy red suits if I could find them! They don't seem to exist...

Has anyone had experience using red suits in an outdoor setting? Would they clash with yellow colouring ? - ie. golden grass? Would hot pink be a better option? (Or would this introduce the same problem as lime of being too reflective?)

To explain the project further, I want to key out the silhouettes of humans so that I can animate their silhouettes with other imagery. I want to key out a distinctly human-shaped hole. In response to your point Dave, yes the figures will be moving behind other objects at times.

Also Dave, I'm not sure who told you Queensland was cloudy... but anyway, you make a very sensible point about shooting under clouds. If it weren't for time constraints...

-----------------------
Director / DP

http://www.lightningstruckitself.com


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Sherwin Akbarzadeh
Re: using Keylight on chroma key suits under sunlight
on Jan 4, 2011 at 1:42:21 pm

It's not built for chroma keying but would something like this pose any problems?

http://www.superfansuits.com/colors/red.html

-----------------------
Director / DP

http://www.lightningstruckitself.com


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Dave LaRonde
Re: using Keylight on chroma key suits under sunlight
on Jan 4, 2011 at 3:45:56 pm

Someone lied to me about Queensland, I guess.

I thing you would still have a MUCH easier time of this if you could move this shoot into a studio.

Since your primary reason for using the suits is to allow the suit-wearer to pass behind foreground objects, is there any way to bring those objects into the studio? You could do a two-color key: green suit, blue background.

Would it be practical to rotoscope the foreground objects, which eliminates the need for a green suit altogether?

Dave LaRonde
Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA


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Sherwin Akbarzadeh
Re: using Keylight on chroma key suits under sunlight
on Jan 5, 2011 at 12:39:48 am

Thanks Dave, but it's crucial that it's a location shoot. I want the characters interacting with the environment (ie. throwing rocks, climbing trees) and this'd be too difficult to fake via a studio shoot.

I'm leaning towards pink suits. In a golden field, I imagine pink providing a cleaner key than red. But I am worried that pink would also reflect more light and I'd have some of the same problems I had with the lime suit.

Here's a matte pink suit that I'm considering (yes, I know it's meant for things other than chroma keying!):

http://www.milanoo.com/Fuchsia-Red-Unisex-Lace-Zentai-Suit-p16069.html

Think it might work?

-----------------------
Director / DP

http://www.lightningstruckitself.com


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Dave LaRonde
Re: using Keylight on chroma key suits under sunlight
on Jan 5, 2011 at 3:59:35 pm

I looked at that suit, and in my humble opinion you've made a fine choice; on the color wheel fuscia/magenta is directly opposite to green, which should work well among vegetation... even a golden field.

You may not be able to avoid roto work entirely. However, if you shoot a clean plate, exposing for the background, and then expose for the subjects in the suits, you may be able to save yourself a lot of grief. It does limit you to mostly-static backgrounds and locked-down shots. If that's not an issue, it could be worth a test.

This has been an enjoyable puzzle. Good luck, and I hope you write back with the results!

Dave LaRonde
Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA


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Sherwin Akbarzadeh
Re: using Keylight on chroma key suits under sunlight
on Jan 5, 2011 at 10:44:29 pm

Thanks Dave,

I like your idea of shooting a well-exposed clean slate for background but I wouldn't be able to use it because my chroma keyed figures are actually interacting with the world around them - ie. throwing rocks - the movement of which would not be represented in the clean slate. But it's a good trick to keep up my sleeve for some of the simpler static shots :)

Thanks a lot for helping me through this one.

Sherwin

-----------------------
Director / DP

http://www.lightningstruckitself.com


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