Correction for light question

[Jay A. Kelley]

We are about to begin a short motion picture which will be using virtual sets for 99.9% of it.

Due to budget issues, we cannot go with daylight balanced lighting.

Therefore I am left to correct over the lens. I would like your recomendations for the best color correction filter for RED when shooting tungstun.

What I want to do here is feed the blue monster enough to keep our noise to an acceptable level.

Suggestions please! Filter brand and number...

Thanks in advance.

Jay

 

[Brook Willard]

Putting a blue correction filter over the lens will lower your effective ASA by at least a stop, generally 1.66 stops or more. So you'll be lowering your effective ASA to roughly 80-100 ASA.

Lighting to 100T will require some pretty serious tungsten heads and a good sized genny. I generally poke fun at such things by saying "if you have the lighting budget for 80 ASA, you have the lighting budget to go daylight."

Now I won't second guess, I figure you've already locked yourself into daylight. That said, have you tried a tungsten lit green screen test? I just came off of my fifth or so tungsten/green shoot and the results are still remarkable. Sure they're not as nice as daylight/green, but they're still cleaner than any other format I've run into [in my admittedly limited keying experience]. I find that the only "trouble" spot is tungsten light on a blue screen.

Have you given it a go?

 

[Hans von Sonntag]

Hi Jay,

I would use a Tiffen 80A. Looses 2 stops but gives you much better DR and less noise. Usually a f5.6 can easely be accomplished in a typical tungsten GS setup at 320ASA. You will be still filming with a f2.8 which is a reasonable stop, IMHO.

I find that RED likes daylight a lot.

Hans

 

[Maz Mawlawi]

What's strange is someone at NAB laughed when our coworker asked about how to deal with the blue noise under tungsten with the RED. They said there was no problem with blue noise and that if we are seeing noise we're making a rookie mistake... Never bothered to elaborate on this...that's too bad since the blue noise under tungsten is till really bothering me...
But having said that, it's nearly not noticable when shooting green screen.

 

[donatello b]

do a TEST using tungsten with newest build 15 ...
IMO never let any light go below 3000 Kelvins = do NOT warm up the talent (no CTO's , warm them up in post) ... get a good exposure on green screen ...

any chance you can put a 1/4 or 1/3 CTB on on green screen lights ..

 

[Dustin Cross]

There must be some differences in cameras. I don't have any extra blue noise under tungsten, but I think I have too much noise in general, tungsten or daylight.

I just did a shoot and some scenes were 2900k and others were 5600k. All was equally noisy. It was pretty low contracts also. When we looked at the footage and saw the noise, we reshot more high contrast lighting set-up (still tungsten) and that got rid of the noise in everything but the darkest parts of the room.

I would test your camera with tungsten and see how the noise is.


Mahalo,
Dusty

 

[Chris Kenny]

Lighting to 100T will require some pretty serious tungsten heads and a good sized genny. I generally poke fun at such things by saying "if you have the lighting budget for 80 ASA, you have the lighting budget to go daylight."

Well, a not-too-uncommon scenario is that you've got a studio space with 100,000 watts of tungsten lighting hanging off of a grid. You have enough light that you can afford to lose a couple of stops to a filter, whereas switching the lights out for daylight fixtures isn't too plausible.

 

[Jay A. Kelley]

I love how I can get help on here. Brook, I have been considering shooting a tungstun lit green screen also. I would then use daylight on the talent. So, you've done this before?

Tell me more about your results in detail. As for the 80a filter... 2 stops is a lot and I don't want to be fighting with a real shallow depth of field on this. I'm thinking daylight. But would prefer to use tungstun on the wall. Thoughts anyone?

Jay

 

[Kenn Christenson]

I don't know if I would want to be mixing color temps for keying. If you can - I HIGHLY recommend doing a test and sending it to the people who will be doing the compositing.

If you're doing tungsten, you definitely do not want to be blasting your talent with the light and heat necessary to compensate for the stop loss of a filter.

 

[Brook Willard]

A great example was on a Petsmart ad a few months ago. It was a 12' x 12' green screen lit with two tungsten fat men. The subject was a furry little dog that was jumping up and down. Combine the motion blur with the light hair and you can imagine what a keying nightmare it could've been. The dog was lit with cool white globes in a fat man. The only reason it was lit with cool whites was because we shot this particular insert in a store, so there was a lot of existing cool white ambient.

I don't have any of the footage [and obviously couldn't post it if I had it], but it was a very clean key. One click. There was noise if I broke the shadows, but it wasn't bad by any means.

As everybody else is saying... do a test! What was acceptable on that job may not be acceptable on yours. It's always worth finding out ahead of time.

If you have some night/moody scenes in your film, do some specific lighting tests for those as well. Compare the noise characteristics between when you light for your final result [I.E. light contrasty] or when you light for crushing in post [I.E. light flatter and curve it to hide the noise].

Mixing temperatures on your subjects and wall... that's tricky. It'll turn the green wall a little warmer than you might hope for. It's not terrible - it is doable - but I don't think it's necessary. Do some tests, even if they're quick and dirty.

Hope this helps.

 

[Greg M]

Jay,
I would advise sticking with one color, you are going to create a mess mixing color temps. And unless you have alot of contrast in the subjects lighting, the "blue noise" issue is not nearly as big a problem when shooting keys. Most of the noise is happening in the shadows and since the majority of your frame is being keyed out, it really shouldnt be an issue. But as everyone is advising, test shots will save your ass. We generally shoot test shots before every commercial that involves vfx work.