Kino super green lamps

[Noah Ward]

Hi,

 

Has anyone lit a green screen using the Kino-flo super green lamps? I need to light a 10 x 30 screen with kino 4 banks and am not sure if I should go with the supers or stick to the regular tungsten lamps. Someone told me that with the supers the extra green spike could bleed onto the talent/foreground. Has anyone had any experience with this? Any suggestions, knowledge or experience shared would be appreciated.

[David Mullen ASC]

Obviously when lighting any chromakey screen with colored lamps, whether Kino Green or Bluescreen tubes, or gelled tungstens, whatever, you have to completely flag the light off of the subject anyway. As long as the Kinoflos are behind the subject and pointed away from them, your only problem should be bounceback off the screen onto the subject, creating green spill.

 

So yes, you need to keep the light for the screen off of the subject, and vice-versa -- it's a good idea to keep the light on the subject off of the screen. Hence why flagging is always important.

 

If you are in a situation where you can't separate the subject from the screen, or separate the lighting, like in a small space or when someone has to walk on a green floor, then an overall tungsten approach may be better, but you won't get the same level of chroma purity in the screen as when lighting it separately with narrow-bandwidth green Kino tubes. The narrow color spike of the tubes wouldn't naturally "bleed" any more easily though -- that's just a matter of flagging the direct Kino light off of the subject.

[Noah Ward]

Thanks David!

[Adam Frisch FSF]

I have used them and they're very good - much better and evener than using white light. They'll make your screen sing like a choir!

[Phil Rhodes]

Hi,

 

My current job (which I am not allowed to talk about) is using them; they're superb. They don't actually look all that screamingly green to the eye - certainly not as green as the blue ones look blue, but as Adam said they make the screen spark up with an almost self-luminescent glow.

 

Highly recommended.

 

Phil

[Chad Stockfleth]

This might be a stupid question (though supposedly there is no such thing ;-) but do you use the green colored bulbs on a white wall or in ADDITION to your greenscreen. As I type this, I'm thinking it is in addition, but just to be sure. Could you shine them on your white cyc and *presto!* have a greenscreen? Sure would save me lots of Rosco Paint....one can dream.

[David Mullen ASC]

Since the Kino Greenscreen bulbs are so narrow in bandwidth, you could in theory get an adequate green color on a white screen -- the problem is that white screens are so naturally reflective that killing all other non-green ambient light on the screen would be very difficult, and it wouldn't take much stray light to wash out the green from the tubes unless you lit to a really high level using a LOT of greenscreen tubes. You'd almost be better off with a gray screen...

 

But if you're trying to save money, since the light from the Kino Greenscreen tubes are narrow-spectrum, you could use cheaper green paint I suppose as long as anyone using your green cyc knew that it had to be lit with Kino Greenscreen tubes.

[Tim O'Connor]

Since the Kino Greenscreen bulbs are so narrow in bandwidth, you could in theory get an adequate green color on a white screen -- the problem is that white screens are so naturally reflective that killing all other non-green ambient light on the screen would be very difficult, and it wouldn't take much stray light to wash out the green from the tubes unless you lit to a really high level using a LOT of greenscreen tubes. You'd almost be better off with a gray screen...

 

But if you're trying to save money, since the light from the Kino Greenscreen tubes are narrow-spectrum, you could use cheaper green paint I suppose as long as anyone using your green cyc knew that it had to be lit with Kino Greenscreen tubes.

 

Hmmm,

 

David, my local high school is always attempting to improve their (blue-screen) chroma-key shots and

I was able to help them separate lighting talent from lighting the bluescreen, using tungsten for

everything.

It worked well and they were pretty happy; I eliminated the spill that their set-ups were getting but

using green or blue lights is a new trick to me and a cool one!

 

Would they get a richer, deeper blue screen if that were lighted with blue-gelled lights and if so, could you

recommend (as specifically as possible if you could) what gels should be used? I'd be glad to go buy

them. It's nice to be the good guy once in a while.

 

Thanks!

Edited June 27, 2006 by DPinthewilderness

[David Mullen ASC]

Getting a purer, more saturated single color out of the screen is only part of the process -- the color depth of the camera / recorder matters too.

 

I would think any blue gels that are purely blue (not actually containing other dyes) would help, but would also cut a lot of light output too from a tungsten. You'd have to do some research into that, but I wouldn't be surprised if even a few layers of Full CTB or using Congo Blue helped cut some other non-blue wavelengths.

[Tim O'Connor]

Getting a purer, more saturated single color out of the screen is only part of the process -- the color depth of the camera / recorder matters too.

 

I would think any blue gels that are purely blue (not actually containing other dyes) would help, but would also cut a lot of light output too from a tungsten. You'd have to do some research into that, but I wouldn't be surprised if even a few layers of Full CTB or using Congo Blue helped cut some other non-blue wavelengths.

 

Thanks, David.

 

The media teacher at the high school is a friend and around during the summer so we can definitely

do some tests, both with gels and with the school's video cameras, which have menus to adjust the

chroma information recorded. Yes, they don't have a lot of lights, and not very powerful ones either,

so I may have to see if I can help them find some additional units to compensate for the lower light

levels when the gels are used but this will be a fun and worthwile endeavor.

 

By the way, this occured to me regarding " a few layers of CTB" :

When combining CTBs, or CTOs for that matter, isn't there some strange math in that say two CTBs

combined is not exactly the same effect in changing color temp. as one might expect? for example, if

Gel A drops a 5600K source to x degreesK, then adding an additional identical gel, B, is not going

to simply drop the color temp. the same additional amount but rather combine them to do something

different? (I'd just go out and meter this but my color temp.meter is MIA; I don't have the money just

yet for a new one and I bet you probably can explain to me the MEANING of whatever my meter results

would be anyway, if you would be so kind.)

 

I have another question but it's different so I'm going to post it as a new topic in the lighting forum

regarding shooting sunrises and sunsets. If you could look at that I would really appreciate it.

 

This forum: getting to talk to all these people- it's just great. Thanks to everybody.

It'd be like if when I were a kid and wanted to know how to throw a curveball, instead of asking

the best pitcher in town, I could go on a forum and talk to Nolan Ryan or somebody!

[David Mullen ASC]

Shifts in color temp have to be calculated using MIRED values, not color temp numbers, because it is not simple addition of color temp numbers. The gel makers list the MIRED shift values for each gel in the swatchbook. For example, Full CTB has a MIRED value of -131, so two layers in theory have a shift of -262. From that you can determine the change in color temp using some math. See:

 

http://en.wikipedia.org/wiki/Mired

 

Of course, this does not mean that gels shift exactly like they are supposed to.

 

Also, we're not talking so much about color temp as we are color purity -- some green mixed into a blue is not necessarily going to change the color temp.

 

By the way, we have an unofficial policy here of asking people to sign their posts with their real name. If I'm going to take time answering questions, it would be nice to know who I'm talking to.

[Tim O'Connor]

Shifts in color temp have to be calculated using MIRED values, not color temp numbers, because it is not simple addition of color temp numbers. The gel makers list the MIRED shift values for each gel in the swatchbook. For example, Full CTB has a MIRED value of -131, so two layers in theory have a shift of -262. From that you can determine the change in color temp using some math. See:

 

http://en.wikipedia.org/wiki/Mired

 

Of course, this does not mean that gels shift exactly like they are supposed to.

 

Also, we're not talking so much about color temp as we are color purity -- some green mixed into a blue is not necessarily going to change the color temp.

 

By the way, we have an unofficial policy here of asking people to sign their posts with their real name. If I'm going to take time answering questions, it would be nice to know who I'm talking to.

Thanks David. I appreciate you're taking the time and I guess that I can sign in from now on with

my name.

I guess that I've liked the fact that I've been able to ask with anonymity some questions

here that people who know me - and there are several who are members here -would likely expect

me to know.

I do a decent job of lighting and shooting and even though I've of course seen mired values given

before, and even know that MIRED stands for micro reciprocal degrees, I'm not proud that I never

learned how to use them or learned some other things for that matter.

 

Thus marks the last anonymous post of DPinthewilderness.