HELP with Chroma Key!
Tech Geek
nobody was able to help me . . . hopefully somebody here could!
Anything is much appreciated:
I am the lead technician at my school in Ontario, Canada. Every morning
we have "announcements" during which students announce school news and
the principal speaks for a couple of minutes. We have been doing it
the same way for years, using an old Panasonic WJ-MX20 as our video
mixer, and a cheap Radio Shack board as our sound mixer (the
announcements are broadcast live through all the TV's in the
classrooms).
Anyway, the other day I decided I would try to use the Chroma Key
effect built into the Video Mixer (WJ-MX20). I understood that a green
or blue screen works best, but at the time I only had a simple white
canvas. As far as I'm concerned the white wouldn't do a good job as
skin pigments are mainly white, along with clothes, etc. However, I
wanted to make sure the effect worked at least decently and in the
right way before I painted the canvas green.
I checked with the instruction manual (availible online) and followed
the directions very carefully. I put a student in front of the canvas,
put the camera on the student and canvas background, selected the
camera on the B-BUS (it's a two bus board (A and B)) as told by the
directions, and put the picture of a mountain scene on A-BUS (coming
from the computer). To activate green screen, you use a little curser
on the preview television hooked to mixer to select the background
which you will be "changing". I did as the instructions said, pushed
enter, and it did the opposite of what I wanted! It made most of the
student mountain-designed, and the white canvas . . . white. I tried
positioning the curser over the student hoping that it might work and
it did the same thing!
If anyone out there has any idea on what to do, I would appreciate it
GREATLY. Thank you very much!
Alexander Tingle
Tech Geek
Richard Crowley
> Hi! I've already sent this message out to rec.video.professional, but
> nobody was able to help me . . . hopefully somebody here could!
> Anything is much appreciated:
rec.video.professional is not active. It is a moderated news
group which means that messages get propogated only after
the moderator gates them. But there is no moderator, so no
messages are being propogated except accidentally by a
few mis-configured news servers. I am using one of the
largest news servers on this planet (Supernews) and no
messages have been propogated in r.v.p for 2-3 years.
> I checked with the instruction manual (availible online) and followed
> the directions very carefully. I put a student in front of the canvas,
> put the camera on the student and canvas background, selected the
> camera on the B-BUS (it's a two bus board (A and B)) as told by the
> directions, and put the picture of a mountain scene on A-BUS (coming
> from the computer). To activate green screen, you use a little curser
> on the preview television hooked to mixer to select the background
> which you will be "changing". I did as the instructions said, pushed
> enter, and it did the opposite of what I wanted! It made most of the
> student mountain-designed, and the white canvas . . . white. I tried
> positioning the curser over the student hoping that it might work and
> it did the same thing!
You seem to understand that you cannot use white as a
key color, but if I were doing "experiments" like you are,
I would at least switch inputs so that the camera was on
the A-bus and the key insert on the B-bus. The switcher
may have some sort of preference? But I wouldn't be
surprised if it makes no difference. Nobody keys live
video on white, so the switcher wasn't designed to do it.
Surely you could find some poster paper or something in
some green or blue shades and try them. You could just
put an action figure sitting in front of the blue or green
paper to play with it, you don't really need to tie up a
breathing human for your experiments.
Bill Fright
Tech Geek wrote:
this is a pretty cheap mixer so you have to help it by giving it an
optimim physical set up. I think your post above said you were testing
over white. You also mentioned this would not work and you were right.
First thing I'd do for a test is go to a video rental house and buy some
green seamless. Or go an art store and get the green.
Light the subject and background at a 1:1 ratio (the same light level).
Try your cursor setup.
bill
William Davis
"Tech Geek" <equipeme...@gmail.com> wrote:
This was posted on another group I frequent.
I thought the regulars here might find it interesting.
Who knows how enforcement will play out - but it's interesting how
Washington works, when it comes to making laws, isn't it?
daves...@aol.com
>
> > the other day I decided I would try to use the Chroma Key
> > effect built into the Video Mixer (WJ-MX20). I understood that a green
> Who knows how enforcement will play out - but it's interesting how
> Washington works, when it comes to making laws, isn't it?
Chroma Key becoming a big political issue?
Dave
nobody special
they used to do in the 50's and early 60's before chromakey. You need
to double-check your camera hookups,a dn make a real green screen,
before you go any further, go buy a 2-dollar (or is it 2-looney?) piece
of he neon-green-looking posterboard available at the corner drugstore
or office supply place. You could also go with blue for chromakey, and
in your situation, that may be more useful. The blue, you could stand
in front of *without* using the keyer, and still have a pleasing
backdrop.
But start small, with a 2x3 foot or so piece of the posterboard. Stick
any old thing in front of that for the test subject, long as it doesn't
have a similar color.
Chromakeys, especially on cheap gear, demand very even lighting. Make a
softlight if you don't have one already, and use the zebra bars
function in your camea viewfinder eyepiece to see if the intensity is
very similar all the way across the green panel. If you don;t have a
softlight, you can make one by making a large tapered box out of foam
core sheets and gaffer tape, attaching it to the barn doors of a
regular video light with wooden clothes pins or metal bulldog clips,
and laying a diffusion material like tough spun or translucent vellum
over the front of the box. More detailed info and safety tips at
vidpro.org under the "cheap tricks" section.
White balance the camera to the light and a white or light gray card,
on the "indoor" filter, before you proceed with the green screen work.
Turn off any other room lights that may be a different colot temp, like
overhead flouros or incandescents, and of course, no daylight allowed
to mix in. Turn off the camera's auto-tracing white balance and
auto-iris. Now make sure you followed the hookup directions correctly
for the switcher; some switchers will only chromakey off a live source,
not a taped one. Roll some tape and try importing the footage into
your NLE editing system of choice to see if it will key at all well in
there. That will tell you if you're in the ballpark for the switcher
live version.
Finally, a great resource for you is at www.dv.com in the forums
section. Ask your questions in the lighting and effects/editing/camera
forums, or if you're shy, search the site's archives for TONS of great
info on everything you need regarding chromakeying.
Richard Crowley
Depends on how it is used.
Likely still people who believe chroma key was used to fake
the moon landing, and who knows what other "news events"? :-)
It appears to be a stray response to the wrong thread.
Tech Geek
I tried using a posterboard that was green and it worked fine. There
is a bit of green border around the subject, however I'm hoping the
lighting will fix that . . . the board was not perfectly flat either .
. .
I was pretty surprised the white didn't work at ALL. I don't
understand why it didn't but . . .oh well. Thanks again for the help.
Alex Tingle
daves...@aol.com
> I was pretty surprised the white didn't work at ALL. I don't
> understand why it didn't but .
Then perhaps you should consider a different svreen name. :-)
Dave
David McCall
"Tech Geek" <equipeme...@gmail.com> wrote in message
news:1137532306.8...@g44g2000cwa.googlegroups.com...
Chroma key looks for a certain hue at a given saturation.
White lacks color, so there is no hue or saturation to lock on to.
You can use white or black for a luma key though.
Luma key doesn't consider color, only video level.
David
Tech Geek
chromakey. If you don't have anything to say about the topic, don't
say anything . . .
Alex Tingle
Richard Crowley
>> Then perhaps you should consider a different svreen name. :-)
"Tech Geek" wrote ...
> Look sir, I'm not stupid, and this is my first time working with
> chromakey. If you don't have anything to say about the topic, don't
> say anything . . .
Please note the emoticon ("smiley face") and don't take it so seriously!
You'll need a thicker skin than that to survive here on Usenet.
Richard Crowley
> Thanks for the help!
> I tried using a posterboard that was green and it worked fine. There
> is a bit of green border around the subject, however I'm hoping the
> lighting will fix that . . . the board was not perfectly flat either .
A traditional fix for that is to use some color to "counteract" the
green reflection. "Bastard amber" is one of the gel colors they
used for that, IIRC.
> I was pretty surprised the white didn't work at ALL. I don't
> understand why it didn't but . . .oh well. Thanks again for the help.
Chroma means "color". There is NO color in white (or black or gray).
It works when the switcher looks for the specified color and then
substitues video from the other source whenever it sees that color.
But "white" ain't any color, so it can't find it.
Bill Farnsworth
Good thing. Bad thing. And another bad thing.
Good thing. Since you mentioned "sir", a few folks here actually
thought you were talking about them.
Bad thing. Since you mentioned "sir", a few folks here actually
thought you were talking about them.
Another bad thing. Not quoting so we all know what the heck you are
talking about and to who. Please quote. and please work on a wee bit
of a thicker skin.
And stick around.
Bill F.
www.billfarnsworthvideo.com
doc
they can be picked up at ebay for less than 50 bux in a felt like canvas.
drd
"Richard Crowley" <rcro...@xpr7t.net> wrote in message
news:11snkf3...@corp.supernews.com...
nobody special
light. When you talk about absorbtive media like paint and ink, then
all colors mixed in equal proportion come out BLACK.
When using green, the correct anti-spill backlight color is a magenta,
when using blue screen, it's the bastard amber or straw.
Alex, usenet is still the wild west of the net; you come here hat in
hand asking for help, you usually get it, but you also usually get some
snarkiness occasionally, consider it part of the 'fee' you pay for the
free advice, and don't let it get to you, that only magnifies it. If
you come into a group with a boastful-sounding handle like you did, you
can expect people to hold you to a higher tech standard, that's only
natural, and the "chromakeying white" thing was a pretty noobular thing
to say. Like asking the airplane mechanic for a bucket of propwash. If
you're being facetious, it didn't come across like that. Best you let
the jibes go unanswered and they'll die off, meanwhile there is good
information to be had if you ask for it...
Regarding your fringing problem, now we know things are hooked up
right, you have to find whatever controls the unit has and tweak them.
I start with even lighting for the BG that looks to be about 40 IRE
units on my scope: you don't need the green or blue to be super-super
bright, that actually works against you - you want the color
information very saturated, so you can make it a little darker as long
as it is even. The fringing may be coming from reflected green "spill"
shining directly onto your test subject. Move the test subject at least
it's own height, plus about ten percent, away from the background and
you'll have less spill problems and less chance the subject's shadow
will contaminate the background as well. yeah, that means the
background needs to be bigger most of the time, but not as big as you
may think: garbage mates and the like can crop out the studio around a
BG and make it look WAY bigger than it really is.
If you still have fringing, try the magenta gelled backlight now.
Still misbehaving? try slowly adjusting the sampled screen color for
hue, saturation, etc. Look for matte controls called "choke",
"clipping", and the like. Twiddle them a bit more on the fly, see if it
improves anything.
If this is still not working well enough for you on the miniature
test setup, your lighting may be inadequate or the gear may just not be
up to the task of live keyeing DV. Dv is harder to key well than analog
or a better flavor of digital with more than a 4:1;1; color space. But
you may have better luck in post using a plug-in, please try that out
and report back.
And thicken your skin just a little bit, pretend it's the annual family
reunion.:-)
daves...@aol.com
> Actually white is ALL colors, blended equally, when you talk about
> light.
That would be "pure" white, which of course never happens in nature
hence the need for white balance on your camera. What we call white
light in practice is always a distribution across the entire color
spectrum and the lower the color temperature, the more it is skewed
towards red.
Dave
Tech Geek
chroma key paint, and plan to paint the canvas in the next few days . .
. we'll see how it turns out.
nobody special
surface. I recommend the flat white latex, water-based primer, brand
name: "Kilz". Kilz comes in a water-based latex and an oil base, do NOT
use the oil base!!! But if you lay this primer down first, your blue or
green rosco paint will work WAY better. It may in fact make ALL the
difference. It's also really cheap, yet reduced the amount of the
expensive blue or green you will need for x amount of surface area.
If you are painting canvas.... like a canvas theatrical flat from your
drama department.... you would need to seal the weave of the canvas
even before you prime it. Wetting even primed canvas can lead to
wrinkles, which are bad for chromakeying.
If I were you, instead of the canvas, I would go to the local home
center and buy an end roll or short roll of their cheapest vinyl
kitchen/bathroom sheet flooring. The pattern or color doesn't matter.
The thing is, the "felt"-like back side, the part that usually gets
glued to the floor- takes paint super-well. So grab say an eight by
eleven or whatever roll of this sheet vinyl flooring, lay it out, prime
it with the KILZ, then use your expensive chromakey paint on it. It
will absorb much less paint than the canvas, so you can keep the
leftover re-sealed can for touchups later, or to use on chromakey props
like boxes, columns, support rods, stools, and etc. (stuff you don't
yet know you will need, but trust me, you will thank me later). Take
two 2x4 wood slats and some contact cement, and make a sandwich across
the short end of the vinyl. Drill holes thru it at several points along
the length and put screws in as well. Now that whole thing can be hung
from two sturdy light stands or with chains and eyebolts from an
overhead grid, or nail/screw the thing into the wall studs. The excess
length sweeps onto the floor, creating a perfect limbo cove for your
keying. The vinyl is flooring after all, so it can handle people
standing on it and the like, which canvas or photog's paper can't. If
they should scuff or scratch it anywhere, well, you have leftover
touch-up for that now. The vinyl "cove" can be taken down and rolled up
for transport or storage, just don't try to roll it really tightly, or
paint may flake off. If you primed it well, this is unlikely to happen.
This setup will work better for you than a canvas flat or a solid wall
of the room. It makes lighting a little easier because of the curving
bottom. The sheet vinyl should only set you back 25 bucks or so.
You'll save at least that much by needing less of the $50/gallon Rosco
paint.
Tech Geek
it took quite that much precision to get it to work well. I will
inform my boss (the prinipal) of the additional materials we will be
needing. I would prefer to have the job done right the first time.
Also, you mentioned "The excess length sweeps onto the floor, creating
a perfect limbo cove for your keying". It is actually better to leave
the excess fabric puddle onto the floor rather than cur it off when it
reaches the floor? Thanks again for all you help . . .I really do
appreciate it.
Richard Crowley
A "limbo curve" makes the transition between the floor and the wall
"invisible" so you can't tell what is in the background. Especially
valuable for chroma keying when shooting head-to-foot shots.
But if you are just shooting people seated at a table, or loose medium
shots (from the belt-up), then it doesn' really matter whether your
screen even reaches the floor.
nobody special
vinyl is essential. Just painting the floor around the base is never
going to work as well, particularly if you are using the lower-end
equipment and software. Do it right, do it the way I described, or
spend countless hours doing rotoscope work later... or just giving up
in the end. It's up to you. Just because you may not be shooting
full-body shots *today* doesn't mean you never will. You can't do a
*really* good weatherman bit without it, for example. But consider: the
beauty of good Ck setups, especially for school productions, is you
need not stress out about location shooting and all the hassles, costs,
and time that takes: you bring the locations to YOU, whether that's a
virtual-reality world, or a re-creation of something historical, or a
dramatic setting, or just really HUGE graphics... you need the
full-body shot capability at some point. The vinyl is really cheap: you
probably spent more money on itunes downloads or buying xbox titles
this week than you will on this, and it will last until you get sick of
it and tear it down. if you ask really nice at the flooring store, with
a note from the principal, it's not impossible they may just GIVE you a
hunk of the flooring from some roll-end that will never sell because
it's discontinued or ugly or something. Long as that bottom side is
clean and without creases, it's perfect for your use anyhow. I once
got such a roll-end for a set wall project for five bucks, just so the
guys could get rid of it.
If you didn't go to the Dv.com lighting forums site yet and look up
John Jackman's extensive online articles on chromakey for DV with
pictures and diagrams, you are really shorting yourself. Look closely
at the way he lit his garage rig, in particular. It's free, just
register, and you can ask him anything and usually get an answer within
the hour.
black...@aol.com
As I recall, the M20 is one of those frame-sync switchers with
composite inputs. The CK is crappy to begin with, but the composite ins
make it almost impossible. Even cheap switchers from the same era use
the Y-Pb-Pr (RGB) outputs of a camera control unit to do a pretty good
CK. Bigger places use Ultimatte or some other advanced system.
I don't know if anybody mentioned it: Green is the preferred color. You
want a background color that the "talent" does not have in their
clothing or eyes. People are more likely to wear blue clothing than
green, and more likely to have blue eyes than green. Hence, green is
the less troublesome color. Don't let the green reflect onto the back
of your subject. Be advised that pros consider chromakey a very
amateurish effect, in many cases.
Tech Geek
blue is a more commonly worn color by the students. Regarding the
paint though, I bought the spray-paint chromakey kind, as that is what
the store recommended. I could easily, however, return it in exchange
for the liquid paint. What kind is more advisable to use?
Thanks,
Alex Tingle
nobody special
cans in pints and gallons. It's usually too thick for an airbrush or
rattle can. Spray would, if applied correctly, end up better, but for
the floor vinyl backing, I used foam disposable brushes and rollers and
it was fine. What brand is this paint? If I wanted the "real thing",
there are only three choices in this order: Ultimatte, (the best)
Rosco, and maybe GAM. Now, I have not bothered to use "real'
50-plus-dollar Untimatte paint for some time. But I have access to very
good keyers, and that gives me more latitude. I take a sample to Ace
and have them mix up a computer match in a 10-dollar latex flat, and it
works ok. Then again, I have also used stuff like $5 matte-finished
plastic picnic table runners from the party store with success. I spend
a lot of time on the lighting and I have access to good keyers, and
sometimes even *i* don't get it as perect as I would like. T.G.'s
switcher may or may not be up to the task, but certainly if he has any
sort of computer editing system, he can do it with that.
nobody special
amateurish effect, in many cases."
Yeah, I couldn't enjoy Sin City, Star Wars or King kong, because of all
the video pros complaining about the keying. I had to walk out of the
theater, the din was so cacophanous.
Blackburst, you sound like you are intimate with the switcher in
question, but reading the rest of the thread first may have been useful
before posting. These are school kids; I don't think they'll be held to
the same standards as Rodriguez, et al.
I say more power to them, because a great deal of modern TV production,
especially in commercials, involves compositing and keying.
David McCall
Usually, you have to go to a shop that sells or rents professional
lighting equipment and hardware.
What you have may do fine, we can't tell from here. Several have
claimed to have success with paint mixed at the paint store.
Paint sold specifically for chromakeying has very pure color of
a specific hue. Usually blue or green. Ultimatte paint is the same,
except that the paint has to meet ultimatte's specs, and I think
the hues for Ultimatte Blue and Green may be slightly different,
than the normal Chromakey colors.
All of that being said, if you are doing blue screen and somebody
walking on the set in bluejeans, their legs may disappear. bluejeans
aren't very pure, so anything will work. It's all a mater of how well it
works.
David
nobody special
purple, whatever. Blue was the most common choice because it has less
than any other color of the reddish shades that are in human skin,
making it easier to key a face and body. The green came later, after
the pigmenting process for that color was perfected, and obviously,
nobody wears THAT shade of green, not since the early 70's, so it's
easier to use if you wear blue jeans or whatnot. (Yes I come from a
time in the dim past before "neon" or "floursecent" color pigments were
commonplace. And they had chromakey then!)
If you were wearing a lot of yellow, Blue BG would work much better, as
it's directly opposite on the color wheel and yellow is right next to
green. In Hollywood, for a brief time the preferred BG color for matte
work was a kind of bloody orange, but I have not seen that for a long
time, I think it was a custom deal that only worked with a particular
film stock and process. As to other reasons for blue preferred over
green; if you get spill or fringing, the blue fringe is much more
attractive to the eye than neon lime green; sometimes the blue spill or
fringe isn't even noticed in the final comp, where it would stick out
like a sore thumb using green. And as I said before, the blue wall can
also be used *without* keying, as just a pleasant neutral BG on it's
own. Nice to get double-duty out of a setup.
There is a technical reason for "digital green" to be preferred these
days: Dv cameras get their green info off the luminance channel, so
theoretically at least, you get a slight improvement in color
resolution with the additional green/luma combination. I think it can't
help any extra unless your gear is specifically set up to use that
difference. Meanwhile, Dv cameras with a 4:1:1 color space tend to make
inferior keys to analog, which has more chroma information. Sometimes,
going retro in your tech actually gives better results.
One other tip, Alex, try turning down the detail control in your
cameras a little: these Dv camcorders are often set preternaturally
high by the factory and people who think over-amping the detail makes
things look sharper or "crisper". That will also add some ringing and
tearing on your edges from over-modulating at the line between matte
and fill channels. Turn the detail down to "normal" or even a skosh
lower, and the key will actually look better/sharper, with less
ailiasing.
David McCall
special for this poster. You have given him a lot of excellent clues, and
I think many of us that have been around as long as you have may have
appreciated the refresher as well. Thanks.
Just to add a couple bits of trivia. The orange they used for matteing
in film was the light from sodium vapor lights, much like what you often
see in parking lots today. The trick was that those lights put out an
extremely narrow spike of orange that could be filtered out in the lab
to pull a matte. Of course the down side is that it is pretty close to skin
and popular costume colors making it a bit tricky.
Studio cameras all used to put out a clean Red Blue and Green
signal right off the preamps of the tubes that pick up those colors.
Blue and Green are right there perfectly clean. It made creating a
chroma keyer relatively simple. Red is of limited value because it
is so involved in skin color. of course there was no spill suppression
or other features we count on today. All you could do was cut a hard
edged hole that you could use as a matte.
Ultimatte changed the world of keying by creating very fancy boxes
that had spill suppression and the ability to extract natural looking
shadows,
soon they could even deal with frizzy hair, smoke, glasses, and other stuff
we used to have to avoid. They single handedly revolutionized keying
for video. It still wasn't easy, but at least now it was possible to make a
natural looking color key. Of course now all of the software keyers have
these features. Unfortunately, DV has thrown a wrench into the works.
The heavy compression now makes keying a bit harder. Some software
claims to have overcome this issue, but I have not tried it.
Another bit of trivia is that Chromakey is actually the registered name
used by Grass Valley for their keying system (one of the first keyers
that actually worked well). I believe the proper generic term is color key.
David
black...@aol.com
nobody special wrote:
> "Be advised that pros consider chromakey a very
> amateurish effect, in many cases."
>
> Yeah, I couldn't enjoy Sin City, Star Wars or King kong, because of all
> the video pros complaining about the keying. I had to walk out of the
> theater, the din was so cacophanous.
Well, there's something of a difference between rookies CKing
themselves over cheesy video and a studio using green screen (a
different process) for serious compositing.
>
> Blackburst, you sound like you are intimate with the switcher in
> question, but reading the rest of the thread first may have been useful
> before posting. These are school kids; I don't think they'll be held to
> the same standards as Rodriguez, et al.
Up until a couple of years ago, I taught TV production at the college
level. I was giving a bit of sage, avuncluar advice to the guy: Rarely
does a traditional RGB CK look good or convincing, but rookies love to
overuse or misuse it. Composite CKs on a frame sync switcher are even
harder to "clip out". Some people in this group enjoy a little real TV
tech talk once in a while.
Unrelated, my students used to love to do wipes and dissolves during a
hard talk multi-camera segment. I would tell them to watch TV and see
that the pros do (cutting).
>
> I say more power to them, because a great deal of modern TV production,
> especially in commercials, involves compositing and keying.
And it can be done well with the right equipment and preparation.
Is it wrong of me to suggest that they make it look professional?
Steve King
news:1137779016.0...@g49g2000cwa.googlegroups.com...
>
>
> Is it wrong of me to suggest that they make it look professional?
No. However, as a teacher, it is wrong of you to not be clear in what you
are saying. Quote: "Be advised that pros consider chromakey a very
amateurish effect, in many cases." That is simply not a useful statement
without further clarification, because 'pros' consider chromakey to be a
very useful and creative tool "in many cases". If the pros misinterpreted
what you were saying, how useful was it to the OP? Not very IMO.
Steve King
nobody special
day, and apologize, I get crotchety posting after ten:-)
If you teach TV , you have my respect and gratitude; it was an
avuncular and quirky guy taeching us in junior high TV with EIAJ RTR
VTR's and B&W porta-packs that put me on the road to the (cough) fame
and (Hack) fortune of my video career. So thanks for doing a hard job.
Probably it was the frame of mind I was in when I read it, but I think
I took you wrong, mistaking your brevity for something else. Whatever,
I'm man enough to say I can be wrong sometimes.
black...@aol.com
About the only time it's used now in real TV, it's the weather map or
an anchor over a computer still or animation, and this is not the same
kind of CK he has in the MX20.
Remember local news in the 60s and 70s? It was the anchor CKed over
moving video, never done any more. Then in the 70s and 80s, it was the
ADO/DVE everybody overused, like a box right DVE-ing out to fullscreen.
Also never done any more.
The dopiest thing my students did was to CK behind a 3 camera talk set.
The foreground changed, but the background remained the same. All with
a cheesy glow around the people.
But I was unclear and opinionated.
nobody special
obsolete MX20, and it's a good learning experience for your kids to
learn about how the perspective and relative position of the BG was not
tied to the camera position. But it doesn't mean they shouldn't try to
experiment. When I was younger, chroma and luma-keyed plastic spaceship
models I 'flew' over DVE starfields entertained me for hours on end.
Nowadays we'd usually do all that in a 3-d animation program, but there
are times keys still get the job done.
In my shop the client one time wanted a new news set and had zero
budget for it, so we put a desk in front of the CK wall, and in a paint
program I whipped up a bank of monitors and "glass" partitions behind
the desk that looked pretty good. Now, to do this right, you need a
heavy-duty computer and something like the ORAD virtual set system,
with encoding pan heads and real-time 3-d set generation... all that
stuff costs LOTS.
I explained about how we couldn't do zooms or meaningful pans, but
that we could run through the script once with the single camera and
backing set up for a wide shot, then I could blow up and blur the BG,
plus zoom in the camera, lock it down again, and record a second take
with the new angle of view and change in persective, and simple cuts
would "sell" the virtual set pretty well. This worked for what the
client needed, and it could work for a student production, if they have
time for multiple takes and editing. Considering the time they would
otherwise spend travelling to locations, it's still a good deal, and
worth trying. The MX-20 may not be up to the task, but Premiere, FCP,
Vegas or Avid can handle it.
I would guess that seven out of ten current TV national spots in any
hour of viewing use keying and compositing to some extent. It's not
always apparent: lots of times it's only subtle improvements or
extensions to an existing set. But you see a LOT of spots for things
like insurance, cars, and hair care products and the like, where people
or products are in exotic technical-looking settings: all these things
are composited keys. AWhen you Watch "exterior" scenes on "ER", a lot
of that is comped in during post, surprisingly little of the standing
exterior sets actually exist.
So I say encourage those kids to really push whatever they have to work
with, even if it may be 'substandard' - because the underlying concepts
are often still valid, and when they get access to better tools and
techniques, they will have some kind of experiential base to refer to,
making their learning come much faster.
Ryan Boni
paints", but not by any recognizable brands!!! The only ones that
seemed semi-legit were for touch-up. It's been a while since I've
bought any, but I seem to remember most actual chroma key paints being
about $50 a gallon.
Also, since I'm sure money is a concern for Tech Geek being at a
school, there are a couple of ways to work on lighting the thing,
inexpensively. The key, of course, to good chroma keying is bright,
even lighting.
If you've already got some kind of lighting grid, make sure the light
is even as hot spots (or dark spots) can play havoc on keying. Try to
separate your subject from the background as much as possible to
eliminate shadows on the background which will cause the strange color
haloing that was mentioned earlier.
If you're just using room lights for your lighting then a cheap way to
help with the chroma key (but will make some people here cringe, I'm
sure) is to pick up some flourescent work lights (as bright as you can
get) and line the top and the bottom (if you can keep them out of
frame) of the wall with them.
And I'm assuming those who say that keying is no longer used outside of
weather forecasting in television haven't watched a lot of local
television advertising (how often do you still see a used car dealer
keyed in over his dealership???)
Oh well!
Ryan Boni
Public Access Director
Peters Township Community Television
nobody special
would put the tube lights along the left and right sides and across the
top, but would leave the bottom bare in case they needed some full-body
shots showing some green floor. Alternate to the flouro tubes, a
small, one-person cove can be adequately illuminated with two home-made
softboxes added to some 1k open-faced lights. You make the boxes with
foamcore board and cover the front with tough frost or tough spun
diffusion. The boxes are mounted to the original barn doors that came
with the 1K, using woode chlothespins or metal bulldog clips.
I know, you're skeptical, this sounds like a fire waiting to happen.
It's not, if you build it right. Details in the cheap tricks section at
www.vidpro.org It's a variation on a design by Bill Holshevnikov.
I've used one of these for hours at a time and it barely got warm.
Tech Geek
nobody special a écrit :
OK then, I suppose that I'll return the paint and exchange it for some
ROSCO liquid paint. Do you think I need to buy a whole gallon, or
would a quart be enough to cover a 7x13 (approx.) foot space? I'm not
sure how much the vinyl flooring absorbs it. . . I will also be sure to
work on lighting once the screen itself is setup and working with the
mx20.
Thanks again, I appreciate it a ton!
Alex Tingle
nobody special
it's a flat latex with a really saturated color, it could well be fine.
Got a picture on a web site somewhere, or the URL of the maker? What
brand? I'm trying to save you money; the Rosco or Ultimatte is "the
shiznit" for chromakey, but it may be expensive overkill if "Gordon's
Beauty Boat and Snowmobile Paint" works ok. Without knowing or seeing,
I can't tell. I am however skeptical of using aerosol cans for CK -
I've never seen one like that: typically the CK paint is too thick with
pigment to flow well in an airbrush or gun, and thinning it for
spraying cancels out it's special properties. Who exactly is the guy
that tried to sell you this spray paint, what kind of store was it, and
what's his credentials? I want names!!!:-)
Whatever else, DO NOT FAIL to PRIME the surface FIRST. Or even the
expensive stuff will dissappoint. To recap, latex water based KILZ
brand flat primer is what I swear by.
As to gallons versus quarts, a gallon, carefully and economically
applied, will probably cover the vinyl I suggested with plenty to
spare, and you want to save that extra paint, seal it tightly, for
later touch-ups or to paint a prop item that you will need to make
"invisible" some time in the future. A box about the height and width
of a piano bench would be useful right away for many things, (only
paint the sides that face the camera, don't waste expensive paint) as
would a stiff, vertical panel about 2 feet wide and high as the set
top, to use as a doorway or column edge to walk in from behind. The
rest of the edges you fill with masks or garbage mattes in post.
Also save out a one-foot square swatch of the paint you choose, (on
white foamcore) put it away somewhere safe and dark, so you can take
that to the hardware store paint computer in the future and match it
with the cheaper stuff, or take it shopping when looking for other
green items.
Tech Geek
"http://us.st11.yimg.com/store1.yimg.com/I/cinemasupplies_1882_15798173"
Again, it's no big deal for me to return it, so if you think it's junk,
say so. My first and foremost priority is to get it done the right way
this time, even though our crappy mixer might not do a good job. In
the near future, we may be purchasing a new mixer anyway.
Richard Crowley
Its "Camera Tested"! :-) It might just work. Who knows?
The biggest advantage of the "name brand" expensive chroma paints
may be their long-term (lot-to-lot) consistency. But if you are doing
it all at once and don't expect to buy more later to match, it is worth
a try.
nobody special
gonna do it. The spray will also get paint dust everywhere in the
studio space, with lots of overspray. I'd go with the precision and
control and les slop of foam brushes and rollers and paint in a gallon
bucket. Wash the brushes out well, and you can use them for the priming
AND painting step.
Whether that's Ultimatte/Rosco or local Ace hardware paint dept.,
matched to a good swatch, is up to your wallet. You can find some good
color samples online (and get a free swatch book mailed to you for
asking) from rosebrand out of New York, (google it) They are the best
deal around for chroma cloth, use the cloth samples in the swatch book
to match paint with at the paint store. Remember, you don't want any
yellow pigment if you can help it. (Yes I know yellow and blue make
green, silly, but there's a difference between mixing two pigments into
a base and mixing one green into the base) Less lemon shade, more lime
shade. Make your choice, Alex, and then let's see what you can make
this baby do!