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HMI and Green screen

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Robin Probyn
HMI and Green screen
on Jul 4, 2009 at 1:26:24 am

Hi there

Any issue using un gelled HMI,s and green screen? shooting video DVCpro HD tape.



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Ernie Santella
Re: HMI and Green screen
on Jul 4, 2009 at 1:54:27 am

Your question is a bit confusing? What are you asking? HMI lights are daylight balanced (most of the time, slightly above daylight temp.) If you are using ungelled HMI's with a green screen, your key and fill lights just need to be balanced to match them. If everything is balanced color temp-wise, then you're good to go.

Shooting on DVCProHD is just a a format, like HDCAM, BetaSP etc, that doesn't make any difference. The only thing to concern you is, is every thing matched correctly... Camera color balanced to the lights, the ratio of source to the background, all the lights color balanced equally etc.

Are you asking something else?


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Robin Probyn
Re: HMI and Green screen
on Jul 4, 2009 at 2:02:10 am

Hi there

Thanks for the reply.Yes I know DVCpro is a format,I have my own HDX900,just thought I put it in as extra info.

Yes you have answered my question.. just had a thought if from the editors/post side of things if they had a preference for tungsten or if anyone had some quirks with having green screen lit by HMI,s

Didnt think they would but just interested to hear..

Thanks again



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Robin Probyn
Re: HMI and Green screen
on Jul 4, 2009 at 2:29:28 am

Hi Ernie

What would be your recommendation for foreground to back ground lighting ratio,s..

Thanks again as always for your help.



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maurice jansen
Re: HMI and Green screen
on Jul 4, 2009 at 7:42:49 am

hi there

ernie said
Shooting on DVCProHD is just a a format, like HDCAM, BetaSP etc, that doesn't make any difference.

that's not completly true doing Chromakeys with a 4:1:1
format is harder than with a 4:2:2 format (DVCpro is 4:1:1)
so if you have a choice try to find a format in 4:2:2

maybe an external recorder on the output of your camera

greet
Maurice



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maurice jansen
Re: HMI and Green screen
on Jul 4, 2009 at 8:06:55 am

oops

forgot that DVCproHD is 4:2:2

you have a good setup


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Robin Probyn
Re: HMI and Green screen
on Jul 4, 2009 at 6:41:24 pm

Well it was a question about Green screen in post.. you might just want to have a nice cool drink..

peace and love



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Dennis Size
Re: HMI and Green screen
on Jul 4, 2009 at 8:08:09 pm

Assuming you're lighting your greenscreen and your talent BOTH with HMI sources you should be fine. Just balance accordingly.

I would diffuse the HMI scources heavily. Light tough spun (Rosco #106) would be my diffusion of choice on the greenscreen.
I would diffuse the talent HMI's with light tough spun and 1/8 CTO .... and also perhaps Cosmetic Highlight (Lee 188).

DS



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Robin Probyn
Re: HMI and Green screen
on Jul 5, 2009 at 2:15:02 am

Thanks Denis

Yes the HMI,s will be through silks,or diffusion frames.. like the idea of the 1/8 CTO for the hero..

Many thanks



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Mark D'Agostino
Re: HMI and Green screen
on Jul 6, 2009 at 2:38:50 pm

I tend to light my greenscreen to about a 1/2 - 1 stop below key. I also found that adding green gel actually gave us a better key.
I shoot with an HDX900 and have found we have to work a bit harder to pull perfect keys because DVCProHD is compressed evn though it's 4:2:2. In theory, (since we don't own one), a camera using an AVC Intra codec would propbably do a better job pulling keys but we own the 900 and its shoots beautiful pictures so we make it work for the green screen stuff. I'm be curious if anyone else agrees with that.

Mark D'Agostino
http://www.synergeticproductions.com


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Dennis Size
Re: HMI and Green screen
on Jul 6, 2009 at 8:34:29 pm

I also found that adding green gel actually gave us a better key.
I shoot with an HDX900 .... and its shoots beautiful pictures so we make it work for the green screen stuff. I'm be curious if anyone else agrees with that.

Mark D'Agostino
http://www.synergeticproductions.com



I agree with you Mark. The 900 shoots beautifully. Normally I never add green to the light on the greenscreen. When I have, it was only because I had LOTS of distance between it and my subject.. or I had a shoddy greenscreen material.
My preference is always to "warm-up" the subject (with either minus green, straw, bastard amber, whatever works best) to separate him/her from the screen. This helps minimize the green bounce "light source" that trys to "tear" my subject away from the foreground, while changing the quality of the light on the subject -- as opposed to the greenscreen.
I always have the greenscreen at least one stop underlit.
Many of my lighting decisions are based on how big the greenscreen actually is, whether or not my subject is also walking around on it, and what type of lighting instrumentation I'm stuck with.
If I'm just doing a simple head & shoulders greenscreen shot I would light it very differently than an entire virtual reality set. Every situation brings with it it's own set of problems.

DS









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Tim Kolb
Re: HMI and Green screen
on Jul 7, 2009 at 3:18:11 am

As one who both shoots...and then has to pull greenscreen composites, there is a couple things that I've concluded.

1. When pulling a screen from a color background, the fact that it's lit over or under doesn't seem to be the primary issue...the key factor is that it's different...over or under. The FX Guide TV guys did a test some time ago with green screens on a Viper camera, lighting at various levels relative to the foreground, and the easiest extraction was pulled from a shot where the green background was lit so brightly that it appeared to be incredibly desaturated. It was simply the shade that was the most distinct from the foreground palette.

2. Daylight lighting seems to help compositing, particularly with skin tones in my experience.

Blue is very nearly across the vectorscope from human skintone and the color of a typical blue screen wall can be moved even more directly opposing if lit with daylight as opposed to tungsten (and this shift becomes even more important with green, as the angle to green is only about 90 degrees) allowing standard spill suppression in most keying applications to work most efficiently.

The other factor to consider is that any video camera is noisier when balanced for tungsten than when balanced for daylight as blue needs far more gain applied to balance with most tungsten sources than red needs with most daylight sources.







TimK,
Director, Consultant
Kolb Productions,


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Michael Palmer
Re: HMI and Green screen
on Jul 7, 2009 at 4:02:02 am

"the fact that it's lit over or under doesn't seem to be the primary issue...the key factor is that it's different...over or under."

I couldn't agree more, if they have the room to separate the green from the subject.

However I believe it is much safer for me when i'm offering advice to the masses to keep the green screen lighting 1.0-1.5 stops lower than the key because I can't assume their situation or skill level to see light, putting them at risk of creating a moster of green bounce that will contaminate their subject.

I also prefer HMI lights and 5600k white balance for green screen work.

Good Luck
Michael Palmer


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Robin Probyn
Re: HMI and Green screen
on Jul 9, 2009 at 3:52:13 am

checked out studio at last.will go tungsten as their over head soft lights are tungsten. couple of 2 ks for the back wall though silks.5k key.. 2k back/side light..

Kino,s for close ups..

Thanks



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Dennis Size
Re: HMI and Green screen
on Jul 9, 2009 at 7:26:22 am

Interesting choices. Why not use the softlights -- and/or the Kinos -- fo the greenscreen backwall?

DS



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Robin Probyn
Re: HMI and Green screen
on Jul 9, 2009 at 8:05:08 am

The kino,s are only small ones.. 20w 4 bank.. too small to really do much on the back wall.. the over heads are pretty much lighting the whole thing very evenly and I think would be ok for a key as it is.

The 2ks through silk,or may just bounce them.. will be very soft.. for the closer shot Iam thinking to switch off the big over heads.. and light it as a straight forward head and shoulders interview.. with the one kino as a key.. make it more moody.. it isnt being keyed into an actual background plate.. so lighting continuity isnt a problem.

What do you think?



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Dennis Size
Re: HMI and Green screen
on Jul 6, 2009 at 8:21:09 pm

You should aso backlight your hero with either 1/8 or 1/4 CTO -- and a 1/4 minus green or even Lee 188 (Cosmetic Highlight diffusion), to minimize the green bounce rimming his/her heroic actions. It sounds like you're going to have a lot of light hitting that greenscreen.

DS



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Robin Probyn
Re: HMI and Green screen
on Jul 7, 2009 at 12:22:20 am

Hi Denis

I thought to cross light the screen with 2 X 1.2 HMI.s through as big as silks the studio has.I,ll have to have the floor lit too,as the hero walks on and then looks to camera(not much moving around)

So not a virtual set,but have to light head to toe..

Any thoughts..?

Thanks



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Dennis Size
Re: HMI and Green screen
on Jul 7, 2009 at 12:34:11 am

That's a lot of "firepower"!
How high, and how far offstage are your 1.2's? A chimera or some sort of softbox to control the spill from your silks will be advantageous.

DS



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Robin Probyn
Re: HMI and Green screen
on Jul 7, 2009 at 12:43:24 am

Guess I was worried about not having enough firepower... studio is big so can back them off..

Do you think 2 X 575,s would be strong enough through silks.. for the back screen.. 1.2 for the key light on the hero,and floor through silk.. 575 as back/side light..

I will have flags for spill..

Thanks



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Mark D'Agostino
Re: HMI and Green screen
on Jul 7, 2009 at 2:30:03 pm

Hi Dennis,
If you add 1/4 minus green and the cto to the backlight and not the key do you tend to see an odd color rimming the back or do you keep it subtle enough to not notice? I'm guessing if I need my back/rim to be bright and white for effect I wouldn't need the correction anyhow since it's already overpowering the potential screen spill.
I mis-typed above and did mean 1-1/2 - 1 stops under key. I always do that because our studio is small and our typical location green screens are in small spaces so I'm trying to lessen green bounce. For simple MS green screens we did indeed get better results when we added the green gel. I obviously can't do that when we are shoot head to toe stuff with the actors moving across the studio.

Mark D'Agostino
http://www.synergeticproductions.com


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Robin Probyn
Re: HMI and Green screen
on Jul 7, 2009 at 2:34:59 pm

How do you deal with having to light the floor(so to speak) if no grid above.Just flood it with huge soft key?and fill?



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Mark D'Agostino
Re: HMI and Green screen
on Jul 7, 2009 at 4:20:05 pm

If it's a large area with talent moving across a wide shot and you see them head to toe, I start by lighting the walls and floor with large soft sources to get everything as even as possible; keeping in mind that you need room for the talent/prop lights With that done I then concentrate on adding the lighting for the talent and props. If you're killing all shadows in the final composite then this is relatively easy. If you want shadow,say a single shadow from a back rim, then I light my talent to match the eventual background and tweak that and the studio soft sources to find a good balance of interesting talent light and even studio light. I avoid a direct back light because of the glare, (There is a gel I found years ago that can be put on your key light that acts as a polarizer. When you rotate the barn doors it kills the glare. This is only useful on a fresnel and I never could use it because it took about 1-1/2 stops from my key and all my sources are relatively small).

Mark D'Agostino
http://www.synergeticproductions.com


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Dennis Size
Re: HMI and Green screen
on Jul 9, 2009 at 5:34:24 pm

Actually a 1/4 minus green ...and 1/8 CTO is subtle. Considering the amount of green light already rimming the subject (via bounce off the screen) the complementary pink serves to negate that. I've actually used full minus green in my backlights occasionally, depending on how much green spill is polluting the subject. Obviously the amber would do the same complementary thing if you're keying with a blue screen.
I like adding a "hint" of CTO to my backlights all the time -- whether I'm chromakeying or not -- depending on the color tonality of the subject's hair (and hair dye!). It adds warmth to people with white hair, vibrancy to people with blond or sandy blond hair, and a warm reflection (instead of a cold white refelction) off the head of someone with black, dead hair. It's all subjective, and a matter of personal taste however.

DS



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Todd Terry
Re: HMI and Green screen
on Jul 9, 2009 at 5:50:55 pm

[Dennis Size] "I like adding a "hint" of CTO to my backlights all the time..."

I sort fell into doing something like that by accident myself. Probably about half the time I do tungsten lighting for interiors (usually smaller locations) and about half the time I do HMI. When daylight lighting I have a small 150w HMI that I built specifically for back/hair lighting (very lightweight so in can hang on a grip arm easily).

One day its ballast was acting up and the darn thing wouldn't strike. I threw up a 300w tungsten Pepper fresnel as a hairlight and was about to gel it for color when I noticed "Hey, that looks pretty good."

I normally wouldn't mix the tungsten and HMI, but in that case it was just enough to give a nice warmth to the backlight. I use that setup often, now.




T2

__________________________________
Todd Terry
Creative Director
Fantastic Plastic Entertainment, Inc.
fantasticplastic.com






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Dennis Size
Re: HMI and Green screen
on Jul 9, 2009 at 11:08:37 pm

We are all merely cooks making a fine meal .....adding spices and "special ingredients" as needed to provide that special flavoring.!

One question Todd ....when you used the 300w tungsten -- instead of your normal 150w HMI -- did you exclaim, "BAM!" :-)

DS



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Mark Suszko
Re: HMI and Green screen
on Jul 10, 2009 at 5:04:34 am

This may be too obvious, my apologies, but my training says to counter spill contamination from Green, you gel magenta on a back/rim light, bastard amber is the "cure" color for spill on a blue screen set.


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Dennis Size
Re: HMI and Green screen
on Jul 10, 2009 at 5:26:03 pm

You are 100% correct Mark ..... but isn't that what I said?

As a sidenote, one should be careful of specific names and various gel company's actual products. For example Rosco's bastard amber #02 (a favorite of mine) is almost identical to Roscosun 1/2 CTO.
Rosco's #01 Light bastard amber however is a VERRRYYY diferent color -- with a lot of pink mixed in with the straw, rendering it somewhat useless as a "foil" to counter balancing the bounce from a blue screen.

DS



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Mark D'Agostino
Re: HMI and Green screen
on Jul 13, 2009 at 1:17:38 pm

Thanks Dennis for the advice. I do tend to warm my backlights often however I also love the look of a cooler, (white,not blue), backlight when doing a warm overall lighting. I'm defintely going to try the 1/4 minus green. By the way, bastard amber is my all time favorite gel.

Mark D'Agostino
http://www.synergeticproductions.com


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Robin Probyn
Re: HMI and Green screen
on Jul 21, 2009 at 11:55:03 am

shoot went fine.The studio had very nice soft lights already rigged in the roof 4 X 4K.. used Kino Image 80,s X 4 and 5K through a silk.. 2 x Divas to float around for close ups.. 2k back light.

Thanks



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Dennis Size
Re: HMI and Green screen
on Jul 22, 2009 at 12:50:12 am

It sounds like you had the perfect equipment complement of gear.
Glad your shoot went well. Thanks for letting us know. Any pictures?

DS



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Robin Probyn
Re: HMI and Green screen
on Jul 22, 2009 at 11:51:53 am

Have some photo,s but it says the file is too big? only taken on iphone.. so dont know how to up load sorry!



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