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View Full Version : Critique my Bluescreen, please.


Daniel-B
06-29-2004, 03:15 AM
Hi guys. I just check out the book "Digital Compositing for Film and Video" from my local library. Anyway, I was eager to try out some of the techniques in the book.

So, I downloaded some bluescreen sample images from a site. Then I composited an image using Discreet Combustion. Anyway, if you guys could critique it for me, that would be great.


BEFORE
http://img19.photobucket.com/albums/v58/PixelMagic/GirlWithBottle.jpg

AFTER
http://img19.photobucket.com/albums/v58/PixelMagic/girlcomposite.jpg

Byla
06-29-2004, 05:25 AM
Man that is actualy pretty good. With some colour correction and a bit of frame to frame fixing it would be quite perfect. And with better light angles.

Ross Forster
06-29-2004, 10:56 AM
Pay close to attention to the hair while keying, you'll find that you've lost all that fine whispy detail in the strands during the process.

Hugh
06-29-2004, 11:32 AM
This is less to do with the keying, but take a look at the bottle... There should be some kind of distortion of the background through the glass of the bottle...

Daniel-B
06-29-2004, 12:39 PM
Thanks for the replies. Actually, Ross, without seeing the matte it does look like I lost alot of wispy hair detail. But that only due to the background bush having almost the same colors as her hair. While I did lose SOME, I was able to retain most of it. Do you guys have any suggestions for getting a better matte on the hair?

Here is the matte for better inspection...

kag122
06-29-2004, 03:00 PM
Hi pixelmagic

I'm not sure how you would do this in combustion, (because i am using shake) but if you get the original bluescreen plate, and run a simple formula.

This consists of

multiplying the redchannel by three and then subtracting this from the blue channel

it should look like

3*r-b

Reorder your the new plate to red and then max it back with you matte.
This will increase your hair detail a lot.

It looks too that you need some blue spill supression happening in your comp. You should reduce the spill until the blue areas turn gray. Again i'm not sure if you can do this easily in combustion because i'm a shake user

Ross Forster
06-29-2004, 03:23 PM
PixelMagic, it was kinda diffucult to make it out in the comp, but I see in your matte you've retained some nice detail in the hair.

You need to work on the CC too, at the moment its too cold. The refraction of the glass bottle needs attention aswell.:thumbsup:

roto baggins
06-30-2004, 05:06 PM
try to work on the blue spill and add some CC.

boomji
06-30-2004, 06:14 PM
did you pull the matte in one pass ???.

try tackling the hair seperately so you can do diffrent spill supressions.

supress the spill on the thigs...the bounce from the asphalt road would have a slight red...slight.

pull a luma key on the bottle, add / screen it over and adjust opacity to taste because youve lost the glint's on the glass.

displace the bg behind the glass a bit
put some red back into her flesh and lift the midtones up a bit


b

beej
06-30-2004, 08:59 PM
Hi pixelmagic

I'm not sure how you would do this in combustion, (because i am using shake) but if you get the original bluescreen plate, and run a simple formula.

This consists of

multiplying the redchannel by three and then subtracting this from the blue channel

it should look like

3*r-b

Reorder your the new plate to red and then max it back with you matte.
This will increase your hair detail a lot.

It looks too that you need some blue spill supression happening in your comp. You should reduce the spill until the blue areas turn gray. Again i'm not sure if you can do this easily in combustion because i'm a shake user

bluescreens & the world of tomorrow, huh kyle?



ya, id say its the spill in her hair & on her legs that is most distracting. if combustion has an expression operator like shake you could also try:

b>((r+g)/2):((r+g)/2)?b (where ':' is if and '?' is then)

that will cap all the blue values below the red & green. otherwise i know you can plot the blue value thats showing up & pull that point down on the hue curve. you might need to restrict it with a selection mask first.

the perspective is a little weird too, it feels like the photo was taken looking down & with a wide-ish lens. if you push her further back into frame & maybe distort/corner pin her lower half so its a little squishier that might work..

good start though & i hope this helps...

Daniel-B
07-01-2004, 02:38 AM
Wow, you Shake guys sure know your stuff. I'm still in college, and I am aspiring to be a professional compositor. However, I don't know how to composite using those math expressions, yet. Just my artistic eye at the moment. However, I may to to re-composite a shot to show you guys.

I'm working on a student film where the two main actors engage in an aerial battle (like the end of Matrix Revolutions). Anyway, in some shots, there will be greenscreen actors composited into matte painted backgrounds. Some shots will be CG doubles of the actors.

Anyway, I'm trying to advance my compositing skills. Thanks for all the advice.

beej
07-01-2004, 02:58 AM
compositing is a fun job, but lots of hrs at times. still, i wouldnt consider doing anything else for a living! not at the moment anyway.


some of the guys here really know their stuff, so dont stop asking questions if youve got 'em.

good luck with your film.

Daniel-B
07-01-2004, 03:42 AM
Thanks beej. Just out of curiosity, do you have any examples of your work I could look at? You seem to understand compositing pretty well. I may show you my progress from time to time. That is, if you don't mind.

beej
07-01-2004, 03:58 AM
of course i dont mind (& thanks for the compliment!). you can check out an old reel of mine at www.vfs.com/~bjones/reel (http://www.vfs.com/~bjones/reel) if you are interested. its missing a bunch of shots but the good stuff is there...

kag122
07-01-2004, 05:09 AM
you may also want to key the shadow seperately so that you have more control over it.

Try getting an average colour value of the whole screen and then subtract it from your original plate. You should end up with just the grey blue areas on the plate(i.e the shadows) that problem with this is that you still have the girl involved. Simply get your key from her and sub it from the shadow key.
You'll then need to reorder it to blue and then use that as a matte to add in your shadow. You may also need to gamma up the alpha slightly to give it a bit more punch.

interference
07-02-2004, 12:42 PM
hi kag122,
i'm new to shake, and i'd like to know which node do you use to enter your expression or where do i have to write it ? (with shake 2.5) beej ? :)
thx

wireFrame
07-02-2004, 01:31 PM
I would just like to add that as a compositor, you should train your eye in finding the correct perspective and field of view for a shot. Try introducing some blurs to the bg as well as the correct distortion.

Another thing is that this is just a still comp; the hair needs a lot of work and when you composite using moving clips, there's that tendency that your mistakes will become more obvious when it's moving.

Also, another challenge in compositing is whether you'll cc the FG or the BG? You can keep the girl's color and the other challenge is to match the bg to the fg--then you can grade the comp to a color that you like.

Regarding conventions in compositing among softwares, I find it interesting looking at how shake adjusts colors. In inferno, we do it using color correction tools and we match it by the eye. Combustion has a powerful keying and color correction tools similar to FFI's.

kag122
07-02-2004, 04:00 PM
hi interference,

With the expression that I am using or beej is using, you'll need to use the colourx node. Just apply it to the colour channel in there.

And if you're really lazy and dont want to learn anything from this at all :) just cut and paste the text below into shake. Its pointless if you dont understand what its doing though,


ColorX1 = ColorX(0, 3*r-b, g, b, a, z);


// User Interface settings

SetKey(
"nodeView.ColorX1.t", "0",
"nodeView.ColorX1.x", "16535.5449",
"nodeView.ColorX1.y", "-3878.052"
);

boomji
07-02-2004, 07:14 PM
In inferno, we do it using color correction tools and we match it by the eye. Combustion has a powerful keying and color correction tools similar to FFI's.

hi wireframe,
just out of curiosity... do you use the color warper much ??? .
a pixel for your thaughts ;)
b

wireFrame
07-03-2004, 12:00 PM
hi boomji!

I seldom use colour warper in tv commercials but in feature film projects here, I use it to match composited shots to live shots; just to be consistent.

I also use it if clients request to cc the skintones on the master edit--it's faster to use this rather than keying the colours out in action.

How about you? Do you use it a lot, boomji?

interference
07-03-2004, 12:45 PM
thx kag122 :)
do i have to write all the text in the bExp line ? because it tell me that the node is in error (excuse my ignorance but it's very new for me :) )
and...just for a try, how does the expression become if it's a green sceen ?
thanks a lot

beej
07-04-2004, 05:02 PM
no, copy & paste that line into shake & it will create a new colour ex node

or if you are going to type it into one yourself, in the blue field just put: 3*r-b

if its a green screen try putting 3*r-g into the greeen field, not sure how well it will work for green but i cant see why not. give it a go.

boomji
07-04-2004, 05:13 PM
hi boomji!


How about you? Do you use it a lot, boomji?

funny i thaught i replied to this yesterday :shrug:

nope our ops dont do much with it and neither do i.May be i still have to get used to it...CC is good enough any way.Some times an add may call for the typical BW look with the talent in color.Even then there's some roto work on top of the color warper.
nice talkin wireframe...u hang out at fxguide much ???.
Have you ever been to the flame user meetings.

b

kag122
07-04-2004, 11:59 PM
no, copy & paste that line into shake & it will create a new colour ex node

or if you are going to type it into one yourself, in the blue field just put: 3*r-b

if its a green screen try putting 3*r-g into the greeen field, not sure how well it will work for green but i cant see why not. give it a go.


Sorry plebian, it actually goes in the red channel :P :banghead:

beej
07-05-2004, 01:29 AM
heh thats what i get for trying to steal your answer!

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