Green Screen with the 5D

L

lasvalley

Active member
Guys, I need your advice on using the 5D to do green screen.

I understand it uses H.264 and has limited color space (4:2:0), and that it is not "ideal" for green screen.

We will be testing to make sure; but I wanted to establish certain parameters going into the camera test to make sure I do everything possible in this stage to help us decide.

Here are my questions:

1) We will be using Kino Flo's for the green screen. Should I favor tungsten or daylight tubes? Someone told me that since the 5D has a CMOS sensor, it would work better for daylight, and that tungsten will be noisier (ala the RED). Fact or myth?

2) If green tubes for Kinos become available to me, should I give them priority over daylight/tungsten tubes? What is the color temp of green tubes: as in, should I set the camera to 3200k or 5500k when using green tubes?

Thank you. Your input and thoughts will be invaluable to me.
 
It's all in the lighting, and in the set-up.
I have had success and it you do some quick searches on-line you will see that there are many others.

As to your other questions...
1) I have not seen that to be true, and use tung all the time.
2) I never use green tubes, just whatever color the lighting is for your subject.

I cannot stress enough to get your subject AS FAR AWAY from the green screen as you can, every foot helps!

Good Luck!
 
I haven't used the 5d on GS yet, but I will say most of these digital cameras aren't great at GS work, you might get away with it but it'll prob take time in post to jimmy the whole thing to a workable image. That being said Red Giant's Primatte + Key Correct Pro is a good one two punch for doing a good job.
 
Sombody on DVXuser had a 5D or 7D and shot a cat puppet with lots of hair. He got a good clean key out, but it wasn't super perfect. But with a little edge blur it could mix pretty nicely. For our feature we had a couple of shots in a car with a Sony V1U (HDV) and our green screen was close to being blown out - but I was able to pull the key and fix the image. A lot is based on what you're willing to do. My scene was more like 60 seconds. Took me about 2 days to figure out what I needed to do and took the computer about 7 days to process, but I had a VFX guy watch my movie and he didn't notice that it was greenscreen.
 
green screen and 5d

green screen and 5d

I have to say that i found the 5d great with green screen, and i owned a hvx200 and a hpx500 and the image from the 5d is the sharpest of them all
 
4:2:0 is going to give you very similiar results to 4:1:1 for chromakeying..maybe even a little better. If you are ok with shooting chromakey with a DV camera than the 5D will be just fine. Especially if you are shooting for SD, an HD downres is going to give you more than enough color information for a great key.

Some things you can do to improve your chromakey work:
shoot vertically and rotate in post. You will get more resolution this way
Turn your sharpness all the way down and sharpen in post
light your background evenly! I don't know if ML has zebra patterns but if it does you can use it to help see if you screen is lit evenly.

I've done bluescreening with the 5D and have had very good results, although it was for an SD project.

My question would be... what will key better on the 5D bluescreen or greenscreen. ON a 3 CCD sensor you could use green blue or even red but whats better for CMOS bayer sensor? I know that for every blue and red color filter there is a green filter on a CMOS sensor because the human eye is more receptive of the color green and sees more noise on that channel. I would imagine this makes it easier to do bluescreen work on a 5D
 
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egproductions said:
I know that for every blue and red color filter there is a green filter on a CMOS sensor because the human eye is more receptive of the color green and sees more noise on that channel. I would imagine this makes it easier to do bluescreen work on a 5D
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I think you have that backwards. Human sight is less sensitive to green, so on a Bayer sensor the ratio is 50% green and 25% red and 25% blue.

I can't say how that affects green or blue screening myself though.
 
Jaime V said:
I think you have that backwards. Human sight is less sensitive to green, so on a Bayer sensor the ratio is 50% green and 25% red and 25% blue.

I can't say how that affects green or blue screening myself though.
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Not 100% sure but wikapedia (granted not considered a scholarly source) says the following:

Bryce Bayer's patent (U.S. Patent No. 3,971,065) in 1976 called the green photosensors luminance-sensitive elements and the red and blue ones chrominance-sensitive elements. He used twice as many green elements as red or blue to mimic the human eye's greater resolving power with green light.

Don't know if that means we see green more or green let's us see more...or both.

I'm going to be running some tests tomorrow and will be shooting on both green and bluescreen with the 5D. Not sure if I'll be allowed to show the footage but I'll definitly post about my findings.
 
egproductions said:
Not 100% sure but wikapedia (granted not considered a scholarly source) says the following:

Bryce Bayer's patent (U.S. Patent No. 3,971,065) in 1976 called the green photosensors luminance-sensitive elements and the red and blue ones chrominance-sensitive elements. He used twice as many green elements as red or blue to mimic the human eye's greater resolving power with green light.

Don't know if that means we see green more or green let's us see more...or both.

I'm going to be running some tests tomorrow and will be shooting on both green and bluescreen with the 5D. Not sure if I'll be allowed to show the footage but I'll definitly post about my findings.
Click to expand...

Reading that, to me, would mean the human eye sees green less, as he had to double the amount to mimic what the eye naturally sees. IMHO, anyway.

Guy has a short video using the 5D Markii for Chroma Key work. You can see it here. While the borders aren't blurred or smoothed at all, and the lighting hasn't been adjusted to properly fit the different scenes, it still demonstrates the 5D getting a good key.

It was also the camera used for the background images :)
 
turns out there was a great thread on cinema5d that talked about this. The human eye is more sensitive to green so a bayer sensor mimics this by having double the amount of green filters. This makes the green channel the least noisy of the 3 color channels.

When lit properly the difference between greenscreen and bluescreen will be marginal because even the bluescreen has some resolution that is comprised from the green channel (R-0, G-3, B-7)

Green screen will generally give you the best results though because it's the cleanest channel but more so because it's the easiest color to light brightly/properly on the visible spectrum.

http://www.cinema5d.com/viewtopic.php?f=34&t=794&st=0&sk=t&sd=a&sid=4411b7b58befa1811663f8cdd2a5850f&start=10
 
Thanks for the links, interesting. I was thinking along the same lines as RandomHero...thought there were more green elements because we see green less, but there's a fancy graph on wikipedia that supports the opposite :)

And from the discussion on cinema5d seems like Green is the way to go.
 
Update -- we tested the 5D and HVX under the same lighting conditions. Winner: 5D!

Question: we haven't tested smoke yet, and unfortunately will not have time for it. Any ideas from our veterans here about how to include smoke with the shot, and still be able to put a good key? Or do we need to shot the smoke "separately": any thoughts?

(To clarify, the scene is supposed to take place inside a room that has lots of smoke in it. Will the amount of smoke interfere with the green screen? We are using a smoke machine. There is a character moving around. Thanks.)
 
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Keying smoke = a bit of a nightmare, depending on the keyer you're using. However, adding it later in post isn't fun either :) You have to stack layers of it to give it some volume, or it looks 2D.

However, you may find that adding it later in post is better, as smoke will exacerbate the "jagginess" that will result from keying at less than full chrominance. (4:2:0) You might have to blur your matte edge too much and the resulting key will look fake.

Do some tests so you're comfortable.
 
ummm. yeah, I did greenscreen with the 7D and it was a nightmare. If it wasn't for the costumes, I would've been screwed. I had to crank edge thinning up to the max and there's still parts where the green is visible. note: this was my first time working with GS though. Click my signature to see the results.
 
your results look pretty good IMO granted your content isn't too hard to key out properly. You say it's a nightmare...compared to what? perhaps you weren't too familiar with lighting greenscreen properly. Green is generally easier to light and key out than blue though.

I've only worked with the 5D but it seems to be a lot easier to key than other formats i've tried. chromakeyeing is always a nightmare in my experience. There's nothing easy about it and nothing that will ever produce perfect results and doesn't take a good amount of finessing to get a nice edge.
 
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