Green vs. Blue? How to do you know?

[Malcolm Desoto]

Usually green for digital. Blue is carried on only one color channel where as green is carried on both one color channel and the luminance channel.

I’m not positive on this. Maybe someone can confirm that.

[Brendan Coots]

People will tell you that green works better with DV footage, but it’s an old wive’s tale.

The choice usually comes down to on-set factors – will the actor be wearing colors containing green or blue hues? If the clothing might lean towards green, use a bluescreen. Blonde hair can tend to key better when using bluescreen (since blonde hair has a fair amount of green component in it).

Both are equally well suited for keying work, but since the choice is dependent on factors you won’t know in advance, you may want to get both.

Brendan Coots
Splitvision Digital
http://www.splitvisiondigital.com

[Sherwood Ball]

Another important factor:

What color are the actor’s eyes?

Keyer’s had big problems with Travolta’s blue eyes
against a blue screen………

G5 Dual 2.5 GHz
6G Ram OSX 4.8
Sata drives
Final Cut Studio 5.1.1, Logic Audio 7.1
PS CS2, AE CS2

[Brian Lynn]

Thanks for the replys!

I knew I had heard people talk about “green for digital” or “blue for something” but I never paid attention lol!

The concept of choosing based on the shot comp elements makes perfect sense, and its what I figured I would end up choosing. The Lastolite surface I want is blue on one side, green on the other, so I will have the flexability to do either.

It seems while looking at all the different manufacturers of green and blue chroma color paints and surfaces that there is some variance in the actual color used… I don’t think this will be a problem as AE and its Key tools/plug-ins can work around that, but is there a preference of one manufacturer over another?

Some of these things are very expensive… and I do understand why the Reflectmedia stuff is expensive, its new, its flashy, and the surface is not cheap with its embedded glass… but on the more standard flat backdrop type, is there really that much of a difference between the manufacturers? Prices range from $200 to $800 on what seems to be almost the exact same thing…

You guys rock, thanks for the help!

Brian

[Brendan Coots]

Green originates in the luminance channel of YUV video signals (i.e. any modern digital video) but that doesn’t matter much when you think about how most keyers work. Keylight, Primatte etc. are all difference keyers, in that they look for the difference in luminance and chrominance (brightness and color, respectively) between pixels. Therefore, if you use a greenscreen your keyer still compares it to a mucky color channel (blue and red) to determine the key. If you use a bluescreen, it will be compared against green and red, so you still benefit from the green channel’s ever-so-slightly improved sampling values.

In short, the keyer uses all channels to create the key, so it isn’t a significant factor in choosing the color of backdrop. What IS significant is on-set factors, per my post below.

Brendan Coots
Splitvision Digital
http://www.splitvisiondigital.com

[Brendan Coots]

The most important thing in a key backdrop is the purity of the color. Ideally you want your final footage to have a background that is pure green (000,255,000 in photoshop or AE) or pure blue (000,000,255). Deviations in lighting, backdrop color etc. will affect this, and as conditions worsen so do your chances of pulling an awesome key.

As for selecting a backdrop, don’t buy anything from Joe Filmmaker on EBay, and if possible buy from a reputable dealer like B&H. They don’t tend to carry total crap products, so you are more likely to get a good product.

As a side note to this, lighting the greenscreen is far more important than most people pay attention to. It mustn’t be understated that your ability to properly light the screen is 80% of its effectiveness. There are tricks that help, like buying a pure green camera filter. When you hold a sheet of white paper up to your lit greenscreen and look through the pure green lens, the paper and greenscreen should be indistinguishable (in an absolutely perfect world). This will tell you how far off the mark you are, and serves as an accurate yet simple visual measurement tool.

Brendan Coots
Splitvision Digital
http://www.splitvisiondigital.com

[Brian Lynn]

Yeah I avoid eBay for most things that I need professionaly. I use B&H regularly. Ever been in their shop in New York? What a trippy place, I recomend a pilgrimage if you ever get the chance!

The lighting is crucial, I know… I will be helping with the lighting and shooting, (and audio, and editing and visual effects as well as we have no budget, just trying to do the best we can with what our regular jobs pay!).

I hope to be able to post a clip soon of something we’ve done, as lots of what we’re planning is based on modified, or at least inspired by, CC tutorials and forum posts!

Thanks for the help, you’ve relieved my fears of investing into the Lastolite product. They are not the B&H top of the line, but the green/blue reversable, at its 10’x24′ size will give us a good work horse.

I would love to invest in Reflecmedia but I think the requirement of the LED ring and how you use it will limit its application, and I can’t afford that much just for a chroma rig at the moment.

Any experience with the Rosco Paint? Seems the cost on it has come way down from the last time I looked…

Thanks again for all the posts!

Brian Lynn

[Sherwood Ball]

I’ve got several cans of the Rosco paint in my garage.
Works fine.

Just don’t over-light it.
Light it evenly.
Do tests: lighting, shooting, capturing, keying.

If you don’t do this, you’ll quite possibly be sorry.
It’s way more work for the CG guys and way more costly.
Spend the time and DO A TEST.

If you’re shooting in mini DV, the DV Garage plug is well worth
the money. I don’t recommend shooting in anything under 4:2.2
color space, but if you have to, you have to.
There is a great DVD on keying by Serious FX.

Taly-ho!!!!

G5 Dual 2.5 GHz
6G Ram OSX 4.8
Sata drives
Final Cut Studio 5.1.1, Logic Audio 7.1
PS CS2, AE CS2

[Brendan Coots]

The rosco paint is good, success with it usually comes down to what surface you apply it to and how it is applied. Obvious construction skills come into play here, like sanding/priming etc. and making sure that moisture does not accumulate and cause bubbling or rippling. Usually not much of an issue unless you live in a humid climate or rush the job.

The last thing I will add is that some GS backdrops are dyed sheet fabric or other thin materials. They can be had for fairly cheap, but are tough to work with. They wrinkle badly, do not give optimal (i.e. even) lighting coverage and are semi-transparent so the light is partially absorbed rather than strongly reflected, making it very hard to get a good saturated color out of it.

Brendan Coots
Splitvision Digital
http://www.splitvisiondigital.com

[William J. meyer]

A few years ago I was at Star Wars Celebration III and someone asked visual effects supervisor John Knoll this same question. He briefly mentioned that caucasian actors’ flesh tone responded better to blue screens, due to the slight green inherent in caucasian complexion.

Take care,
wjm