Jump to content
Sign in to follow this  
Jiban Huidrom

cheapest camera for perfect green screen work

Recommended Posts

How is that?

A scaling without without visible aliasing (without just skipping pixels) means interpolation, averaging values. How can this increase the accuracy of the individual color information?

Share this post


Link to post
Share on other sites
EOSHD Pro Color for Sony cameras EOSHD Pro LOG for Sony CamerasEOSHD C-LOG and Film Profiles for All Canon DSLRs

this guy is a beginner and a 4 2 0 camera is fine for what he whats to do - Ive had alot of pop vidoes broadcast across the world on MTV and all the major music chanels shot on a 4 2 0 camera - you dont need to go spending a fortune on a camera just to do blue screen or green screen - there is alot of smoke and mirrors on this forum of people who read spec sheets and and believe myths

Get your lighting right thats the important bit first.

Share this post


Link to post
Share on other sites

If you want perfect green screen, you need a RAW camera. Three exist in your price range:

 

  • BMCC. This $2k camera currently runs RAW and the picture is phenomenal.
  • BMPCC: This $1k camera should have it's RAW firmware released soon. 
  • Canon 5d3/ML: This $3k camera does RAW when hacked with Magic Lantern.

 

If you are new to the game, go with the BMPCC. It's compressed RAW will fit on SD cards. Soon, you should be able to edit directly in Premiere CC.

Share this post


Link to post
Share on other sites

have you ever actually tried shooting green screen for a 'real project' with RAW

ITS A NIGHTMARE OF DATA MANAGEMENT

as you have massive RAW files PLUS all your layers of added green replacement parts for every cut you do

you need the most powerful computer you can get your hands on to handle all the data as layers add up, and up...

I do not recomend this for a newbie beginner , we use a high end AVID system to work this amount of data

 

Stick to a Panasonic or Canon Camera - learn how to light and how to do good pulls thats the main thing you need to learn

first

Share this post


Link to post
Share on other sites

How is that?

A scaling without without visible aliasing (without just skipping pixels) means interpolation, averaging values. How can this increase the accuracy of the individual color information?

 

It would not be any less accurate than a camera recording that resolution in 4:4:4 color. 

 

The accuracy of the color isn't in question- the resolution of it is. The accuracy of any given pixel is really a side effect of how much resolution each color channel gets. As I understand it, color sampling is reducing the resolution of certain color channels in order to save bandwidth on compressed video. The idea is that your eyes will see the difference in contrast more than the difference in color, therefore not every channel of color needs the full resolution. This is mostly true, as side-by-side the images look identical to the human eye, until you isolate colors.
So when we say 4:2:2, you are saying that for every 4 pixels, cB gets 2 and cR gets 2. If you isolate the red channel in After Effects, and you'll see the resolution is lower than the full image, with the borders around objects much less precise and blocky looking/pixelated Here's an example of this:
800px-Colorcomp.jpg

Top part shows the full color sample, bottom is the resolution of the actual color channels. 

But like any enlarged picture that looks heavily pixelated, if you scale it down the discrepancy between the lost pixels is gone, resulting in a resampled fine pattern around the borders instead of the blocky pixels. In other words, there would be no difference from a picture taken at that correct resolution.

As far as I can tell, this is why having higher color sampling makes a difference to chroma keying in particular, not because it is hard to see what is "green", but because the borders of color aren't as well defined, and it can wreck havoc on the edges of your key. Again, its not about color accuracy, but resolution of the color channel you are trying to key out. 

 

If this is going over anyone's head, there's a great write up here on DVXUser about it:
http://www.dvxuser.com/articles/colorspace/

 

Yes, shooting full res 4:2:0 and even 4:2:2 won't give as smooth of a key as 4:4:4, as the edges are inherently less defined by the very nature of color sampling. That doesn't mean it isn't possible, and that doesn't mean you can't pull of a great key regardless... especially if you are able to reduce the image being composited to clean it up. 

But this isn't just "smoke and mirrors", Andy. Its science. None of these cameras operate on magic. Understanding how it works in order to make an educated decision vs. just recommending perhaps a great all-around-camera is important! He isn't asking what's the best all-around camera right now! There are cameras around the same price point as the G6 that are capable of recording more color information per frame.

I understand what you are saying about RAW file management being a beast- I agree. But a 4:4:4 compressed image, or heck even a 4:2:2 will be far cleaner than a 4:2:0. And that's my own real-world experience backed up with science!

Share this post


Link to post
Share on other sites
4:2:2 is all you need. It sounds like people are trying to give you the best here but not taking into account time management and affordability as a whole package. Most broadcast is keyed with 4:2:2 cameras. You still get definition around hair and fuzz. It is completely manageable. I would never go back to 4:2:0 after working with a live digital key, you notice the difference instantly. Yes the G6 is a great camera, yes it is adequate, but you are going to get more value out of the bmpcc.

Share this post


Link to post
Share on other sites

4:2:2 is all you need. It sounds like people are trying to give you the best here but not taking into account time management and affordability as a whole package. Most broadcast is keyed with 4:2:2 cameras. You still get definition around hair and fuzz. It is completely manageable. I would never go back to 4:2:0 after working with a live digital key, you notice the difference instantly. Yes the G6 is a great camera, yes it is adequate, but you are going to get more value out of the bmpcc.

 

BMPCC is a little pricier, you can get cheaper cameras with 4:2:2 support. Heck, the D5200 supports clean 4:2:2 HDMI out. And to be honest, if you are doing ONLY green screen work, the whole large-chip shallow DOF thing that comes with interchangable lens cameras is sort of overkill too. Small chip = sharper consistent focus, 4:2:2 = cleaner borders around the key. 

G6, meanwhile, is 4:2:0 and large chip. As you say, it will do the job adequately, but it isn't the best value for the money for this specific task.

Share this post


Link to post
Share on other sites
Good points there, I agree about all that. But with the 5200 you need an external recorder, you just doubled the price. I have a bmpcc, I have 3 studio 4:2:2 Sony cameras, I honestly prefer the grading and lack of dof on the bmpcc. Heck, it is 3x crop. Get a good amount of lighting in there and close your aperture. You'll need light for a good key anyway. And then you've got a sharp key and tons of color info. It does lack fine tuning with your key. All you have for that is a choice between film/video look and Kelvin. But it is still my choice under 2 grand. And that is saving you some money.

Share this post


Link to post
Share on other sites

But like any enlarged picture that looks heavily pixelated, if you scale it down the discrepancy between the lost pixels is gone, resulting in a resampled fine pattern around the borders instead of the blocky pixels. In other words, there would be no difference from a picture taken at that correct resolution.

As far as I can tell, this is why having higher color sampling makes a difference to chroma keying in particular, not because it is hard to see what is "green", but because the borders of color aren't as well defined, and it can wreck havoc on the edges of your key. Again, its not about color accuracy, but resolution of the color channel you are trying to key out. 

 

If this is going over anyone's head, there's a great write up here on DVXUser about it:
http://www.dvxuser.com/articles/colorspace/

 

As I wrote, scaling down is about anti-aliasing the edges through interpolation of pixels. What you stated before, that 4:2:0, by merging pixels, get's miraculously 4:4:4, is wrong. 

 

420.png

 

You will never reverse the 4:2:0 to 4:4:4.

 

However, unless you are working in a set like this:

tumblr_mk9xp1WWt91s6mknho1_500.png

 

... you can do with 4:2:0. Because a green screen will have only green pixels in 4:2:0. It's the outlines that cause problems. The Keylight method to blur the edges and mix them with purple is no longer state of the art, as mentioned above.

Share this post


Link to post
Share on other sites

The whole idea of 4:4:4, 4:2:0 and 4:2:2 is, as has been said, the ability to create low-bandwidth video by compromising on color space, which we are less likely to notice (over contrast/sharpness).  

 

The better color information you have, the easier to key.  Andy should write all the people who spent $5,000+ on cameras that do 4:2:2 or 4:4:4 and tell them they wasted all their money ;)

 

Andy, all you need to say is, yes, color keying is easier on a 4:4:4 camera, but for what you want to do, your money is better allocated on a 4:2:0 camera like the G6 and good green screens, lighting and software.  No one here has argued against that!  We've only tried to educate the OP on the issues.

 

You're effectively saying that some of us don't know anything about real-life shooting, only academic theories.  Also, you shoot music videos that are so busy, visually, that no one would notice green in the hair, etc.  We don't know what the OP is wanting to shoot.  

 

It's Murphy's law that one day, Andy, you will get a job where the client will notice the difference.  Remember to report back to us ;)

Share this post


Link to post
Share on other sites

The "cheapest: camera for "perfect" green screen work?

Simple, The Blackmagic Cinema Pocket.

Obviously you can do chromakey work with 4:2:0 cameras, this has been done for many years. but if you really are looking for the cleanest key do you need at least 4:2:2 and more if you need to key hair and translucency.

My basic needs for a good key are:

1. Lighting and subject isolation without spills.

2. Sharpness

Share this post


Link to post
Share on other sites

 

If this is going over anyone's head, there's a great write up here on DVXUser about it:
http://www.dvxuser.com/articles/colorspace/

 

man, ive been trying to wrap my brain around the whole color sampling thing for awhile now, and ive understood it enough to be successful in practice, but conceptually the little illustrations in this article really helped me a lot, thank you dishe! 

Share this post


Link to post
Share on other sites

However, unless you are working in a set like this:

tumblr_mk9xp1WWt91s6mknho1_500.png

 

... you can do with 4:2:0. Because a green screen will have only green pixels in 4:2:0. 

 

 

Axel, I am an idiot, would you please explain why this is exactly? What is the salient feature of this set that makes it so? Why––because the lighting and screen color are so consistent on a stage like this? (I have no idea why being on that set would allow a 4:2:0 scheme to be so much less of an issue.)

 

Again, no irony meant, I'd really like to understand this better, I haven't done a lot of keying as I'm sure all of you can tell smh

Share this post


Link to post
Share on other sites

Axel, I am an idiot, would you please explain why this is exactly? What is the salient feature of this set that makes it so? Why––because the lighting and screen color are so consistent on a stage like this? (I have no idea why being on that set would allow a 4:2:0 scheme to be so much less of an issue.)

 

Again, no irony meant, I'd really like to understand this better, I haven't done a lot of keying as I'm sure all of you can tell smh

 

You are not an idiot, I guess my english isn't very good. With 'unless you work in a set like this, you can do with 4:2:0' I was trying to say that it is not good for 4:2:0, because of the overall spill. The sentence may have been grammatically wrong.

 

If there are roughly 4 pixels on the edges where green and foreground mix in 4:2:0 without any spill, you can imagine how many there will be with a lot of spill ...

 

As human being, with eyesight limited to 4:2:0, you probably see purple dots if you close your eyes in this studio. Personally, I have never been on such a set. But I can't believe that color keying will suffice to get a clean matte for the Peter Jackson team. There will still be some trainees who spend hours and hours on rotoscoping additionally. And you can detect another trick in all LOTR movies: The actors are always backlit. Read jghardings post here.

Share this post


Link to post
Share on other sites

I think what Axel is saying, citizenkaden, is that if you want a nice 3d like chromakey, the background wrapping around the actors, you would build the set like that pictured.  The problem with such a set is that the side walls in green will reflect green light onto the actors and that will confuse the chromakey.  So you want the software to differentiate between green on the screen, and green that has been "spilled" onto the actors.  

 

When I first read about this I thought it was stupid.  Until I tried shoot green screen in a small room and it kept spilling onto arms and hair (that is, a green reflection).  If the OP can't place his actors far enough from the green screen he/she will run into this problem.  dishe's link clearly explains why 4:2:0 does not give accurate pixel level chroma for the software to work with.  Even 4:2:2 is not perfect.

 

In practical terms I would say this,

 

SCENE A: Actors are in big sword fight on some crazy tropical island.  The green screen is in a large room with plenty of room for lights, actors, etc.  A G6 would be fine.

 

SCENE B:  A man and woman are having an intimate talk aboard a "starship" with a window overlooking space.  Plenty of closeups.  The woman has fine, flowing hair.  Then xenogears BMCC is, if you ask me, would be the only chance you have of making it look real.

Share this post


Link to post
Share on other sites

SCENE B

woman on starship by window overlooking space ...close ups - done it !!  in this video on a 5DMK11 ......4. 2. 0

 

my point is it can be done if you know what you are doing

 

http://www.youtube.com/watch?v=dMXfD-vQ5ng

Share this post


Link to post
Share on other sites

SCENE B

woman on starship by window overlooking space ...close ups - done it !!  in this video on a 5DMK11 ......4. 2. 0

 

my point is it can be done if you know what you are doing

 

http://www.youtube.com/watch?v=dMXfD-vQ5ng

 

Andy- hate to be "that guy", but this clip doesn't prove a darned thing.

 

You posted it earlier as well, and as someone else already pointed out there is so much motion going on that you wouldn't be able to spot a clean key versus a messy one in the first place. Not to mention it has been down sized to 480p. I mean, any HD camera downsized to 480p will work according to my explanation above about resampling. I'd say you could have probably shot this on an iPhone4 and gotten roughly the same results. 

 

Just saying.

Share this post


Link to post
Share on other sites

I can't see the video (due to copyright-laws in my country), but your comment makes no sense. Andy surely didn't perform the keying in 480p. Your explanation remains wrong. If a 1080 clip has visible artifacts, they get worse when you downsample the video. Noise is more prominent, jagged edges are magnified, every other artifacts become more visible. Also true for the new 'issue' with the BMPCC: You see almost nothing @1080, but once you downscale the image, the grids pop out. 

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Restore formatting

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Sign in to follow this  

×
×
  • Create New...