Green vs. Blue? How to do you know?

[Brendan Coots]

Great advice, especially the part about over-lighting. This causes desaturation in the backdrop color, and almost always creates hotspots that are a nightmare in post.

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

[William Dempsey]

Hi all,

Chroma key and digital key products are not equal ! My personal tests conducted from 1996 to the present have, at least for me, shown that the more vibrant Ultimatte and digital keying colors function much better and allow the extraction of finer detail. “Chroma key” colors look like mud when placed side by side with products listed as digital key colors and the Ultimatte colors.

While I have several fabric screens I prefer Ultimatte green and blue painted surfaces. The fine muslin screens are as was posted above are not opaque and need to be stretched to get rid of wrinkles. The ones I have purchased have also had a slight yellow bias that makes keying fractionally more difficult than the painted surfaces I’ve used. I have not used the spandex screen material that is supposed to be really good but is rather expensive and limited in size if you want to avoid seams. The retro reflective products are expensive and seem to be a bit limited in size as well. From the days when I did front projection work with 7610 and 7615 scotchlite screens that type of material was also extremely fragile. I suspect the new materials are much more durable but probably not close to fabric or paint. Keep this in mind since I find talent typically does not hear the works “please stay off the screen”.

After meeting with the folks at Ultimatte ,they suggested that we use the smooth side of linoleum flooring which sweeps out nicely and takes paint well as our back drop material for small to medium sized screens. Note it is a bit fragile and can tear if abused. Also if you choose to go this way avoid deeply embossed patterns on the flip side as they can show through when flexed repeatedly. It is a good method of quickly making a high quality screen and moderately inexpensive. The inverted painted linoleum also makes a good keying floor and holds up to abuse very well. It is after all flooring material. The Ultimatte paint isn’t cheap but its easy to fix if marred. I’m still using the piece that I bought in 1997 as a floor extension.

In response to part of inital question, it is my understanding that green is better for video since there is more noise in the blue channel and green has a higher luminance. With film the blue sensitive layer of the emulsion is more sensitive making for better keying with blue. Also I have heard that blue requires more light which may be a consideration. Of course on set color issues are probably more critical. I have keyed with both film and video using both colors and have had good results with both. I should say that I use Ultimatte Blue which is lighter than most other blues even some digital blues .

With regard to on set color also be careful of yellow and yellow orange with green screens and pink and magenta purple with blue screens. I have found these colors can cause problems. Test before you shoot.

Regarding keyers I think all the products out there are good. I personally use DV Matte Pro and Primatte. I typically use DV Matte Pro since it is easy to use and pulls a great key. I have found that there are occasions where Primatte performs slightly better with some problem keys.Specifically, Primatte is a bit better with HDV that is hard to key due to its reduced color depth. Demo everything you can get your hands on and see what you feel most comfortable with.

Hope some of this is useful

Bill

[Leo Mcmichael]

I recently finished a project for a costume
manufacturer which required all the costumes being
shot against green or blue screen. They had some 150
or more costumes, wigs and hats all shot against
either blue or green based on the color of each. I
used a Videonics mixer with blue/green capabilities on
set to “test” the key and to give the client and the
talent an idea of what we were trying to accomplish
during the editing of the video. I did my research
into blue and green and I knew my budget which wasn’t
much and went with the approach that if possible, we’d
shoot against green, if not then blue. I set up the
backdrops which were paper rolls of blue and green at
an “L” configuration so I would only have to basically
pan the camera and shoot against a new color. Easy
set up! Of course that required dual lighting kits so
we didn’t waste a lot of time lighting and
re-lighting.

Now for lights on budget, and to keep colors pure, I
actually went with Craftsman halogen work lights on
stands to light the backgrounds. 250/500 watts
switchable right on the light itself. These worked
great! I used 250 watts on the blue and 500 watts on
the green. I do now find though I should have gone
with 250 watts on the green as well. The lighting
would have been more even to the camera. I was in
between what I saw with my eyes and what I saw with
the camera. I wanted a brighter green and opted not
to trust the camera. Next time I will shoot at 250
watts on either.

Now, to light the models I used incandescent lights
with reflector umbrellas which gave the skins tones
and costumes a slightly warmer look and helped them
stand out from the blue or green a bit more later.
Even with the green being lighter, if I had hit the
floor with some more halogen lights to remove shadows
and fall off darker areas, they’d have been lighter
and I’d have had no problems later keying the greens.

As it turned out, I checked into more keying software
because the FCP keyer was more trouble than it was
worth trying to get them clean. So I turned to
DVMatte Pro and it worked like a charm! It was easy
to learn, and easy to tweak even my toughest keys when
I would pan from the floor to a face and the dark
areas to light areas would be at their worst trouble
for me.

The blue screens worked very nicely! I was surprised.
It had to do with the evenness of the lighting. It
was actually hard for me to use the dropper to find
the lighter portion and the darker portion for the
keyer. That’s a good problem to have evidently. You
want the color to be that even!!!

One costume I was worried about had tie-dyed shirts
with purple as one of the colors and it was no problem
whatsoever. Another costume was of a purple dinosaur
(yes, it’s licensed) and it too dropped out easily!
DVMatte Pro made it simple to work with and tweak, but
the limitations I had were totally with my bad choice
of overlighting the green screen a bit. I should say,
unevenly lighting it. When I had head shots against
green, they dropped out perfectly. Even with blonde
hair.

I did find one tool in FCP worth having that I believe
comes with FCP, that was Matte Magic. That was
invaluable in smoothing out edges and losing those
rough spots that give away the trick.

Now, the end of the story is simple. I finished a 16
minute video which required in most cases 3 sometimes
only 2 layers of close ups, long shots (360) and
medium shots for each costume using DVDMatte Pro in
FCP using garbage mattes to extend backgrounds, Matte
Magic to smooth edges and an occasional color
correction to the green screen before keying it to
smooth out the tones.

Considering we shot the footage of over 150 costumes
with kids, adults and teens in one day from 9am to 6pm
start to finish with lunch and I work by myself, I’d
say that worked out nicely.

So it can be done! And next time, I’ll light much
more evenly against the greens.

NOTE: there was one screen which didn’t work and would
have taken forever with garbage mattes, so I opted to
use Commotion 3.0 Pro and old program which still is
one of the best ever made. It was a baby hat and her
mother was holding her from behind in a green suit
which was too loose fitting and caused too many
issues. Also there was green in the hat that was dark
but matching the dark areas of the green suit. It was
easier to export the clip and correct it using
Commotion.

Sometimes you take what you get on the set and worry
about the fix later. At least that’s what I did
knowing I had Commotion to fall back onto.

Mac G5 Dual 2.3 ghz, 2 gigs ram, Mac OSX, FCP Suite 1, Commotion 3.0, many plug-ins and filters all for FCP. Anything else you’ll have to ask I guess? LOL

[Ray Young]

Hi Brian.
This debate has been going on for years and as a person who grew up in the early years of television and having worked in the industry since the begining of color broadcast I can answer your question simply and easily. A little history is needed here. Back in the 60’s Blue was ALWAYS the choice of broadcast television because blue was the opposite of facial tones and could be keyed easier. Wardrobe was chosen carefully as to not have blue tones in them.
Green was chosen by the FILM industry because film was more sensative to green.
With thay being said, and you are shooting video, and with todyas technology, you may choose any color you wish. I personally carry both colors with me depending on the situation. Fir studio situations and closeups, I normally choose blue.