Blue Screen Test

[Daniel Smith]

Hi.

 

I'm currently making a project which will be shot in about 3 weeks time in a studio, against a bluescreen. We are shooting on HD, progressive, 4:2:2 sub-sampling. (DVCPro100)

 

But before shooting this bluescreen test, I just have a very simple question.

 

How easy is it to key out the bluescreen?

 

We will be using Avid HD.

 

The thing is half the set will be real, the rest will be CGI walls. And there's a strong possibility of shooting behind an actors head and focusing on something behind him. Therefore leaving a blurred actors head against a bluescreen. And I'm quite worried about the bluescreen not keying out correcltly.

 

We funnily enough have persmission to shoot in Brixton prison however, that defies the object of a bluescreen "test".

 

As you can tell I've never yet 'really' done any bluescreen work. But I'd still like this project to come out as nicely as possible.

 

 

If you've done any bluescreening before or have encountered these kinds of problems please give me a heads up of what to expect, what to do and what not to do.

 

Thanks.

[David Mullen ASC]

Well, it partly depends on how evenly-lit your bluescreen is and that you made sure not to have any blue spill on the subject, nor that the subject is wearing any blue. Beyond that, your keying software and your proficiency in using it is probably a factor.

 

As for the out-of-focus head against blue, you should test whether it is better to shoot the object in focus against the blue so you can pull a good matte, and then if you can make it blurry in post before you comp it against the background.

[Daniel Smith]

Well, it partly depends on how evenly-lit your bluescreen is and that you made sure not to have any blue spill on the subject, nor that the subject is wearing any blue. Beyond that, your keying software and your proficiency in using it is probably a factor.

 

As for the out-of-focus head against blue, you should test whether it is better to shoot the object in focus against the blue so you can pull a good matte, and then if you can make it blurry in post before you comp it against the background.

Ok I'll probably just have to shoot the actor in focus and blur it later. (From what I know, it won't look 100% natural but there's not a lot else we can do)

 

As for lighting the screen we have access plenty of kit and a lighting grid so it shouldn't be a problem.

 

Can you reccomend any other keying software? I've just said we will use Avid because that's what we will use to cut it, but I'm open to any other software if it will do a better job. I have After effects if that is any better.

 

Thanks.

[David Mullen ASC]

Someone who does post keying work could answer that question better than me.

 

I would shoot a take with the subject shot to the degree of out-of-focus that you want, so at least you have a reference for how that looks optically.

[Daniel Smith]

Someone who does post keying work could answer that question better than me.

 

I would shoot a take with the subject shot to the degree of out-of-focus that you want, so at least you have a reference for how that looks optically.

It's only a 3/4 minute length shoot that we will probably have done within 2 hours. (2 hours, filming time that is)

 

I'll just shoot both, see if I can key out the blue behind the blur, if not revert to the safety shot. I'm getting hold of Ultra2 by Serious Magic. Apparently that is good for keying out blue behind things such as smoke, water etc.

Edited November 20, 2007 by Daniel Ashley-Smith

[Scott Fritzshall]

My recommendation is that you shoot it correctly against the bluescreen (ie, in-camera defocus), because getting correct defocus blur in post is very difficult. Keying optically defocused material is also very difficult, however, and I'd recommend that you find someone who is more experienced to do it. You'll need to do a lot of spill suppression to get rid of the blue in the transition areas. Really, for this sort of thing, it's best to do the compositing in a dedicated compositing application, such as Shake or Nuke. Shake comes with Primatte and Ultimatte, which are both very good keyers. No keyer is automatic, however, even though most claim to be.

 

Am I correct in assuming that you'll be shooting on an HVX-200? My understanding is that it's best to shoot in 1080P mode even though it's upsampling to get that resolution, simply because it's also allocating more bandwidth when you do. I read something about that a few months ago, but I don't recall where. The compression is going to hurt you as much as anything else. Blocky artifacts along smooth gradients (such as defocused key edges) are really really painful. If you're going for Standard Definition delivery, however, it's not as big of a deal, because the downsample at the end will blow a lot of that away.

 

The good news is that getting good results is not terribly difficult with modern keying software. The bad news is that getting GREAT results can take a lot of experience and even when you have it, it's still very tough.

 

Make sure you shoot it as well as you can. Take detailed notes about every aspect of the camera settings so that you can recreate them when you shoot the other elements. Make sure that you are lighting it in the same manner, and with the same lighting ratios and everything. And of course, try to get your subjects as far away from the blue screen as possible.

[Walter Graff]

Don't shoot out of focus. You are asking for trouble. You can easily defocus in post. While some myths about how difficult green screen is to deal with exist all over the web, it is really quite easy. If you need more help you can email me or call me.

 

Shooting in 1080p will offer you nothing noticable as the HVX shoots progressive frames in it's native resolution of 960x540 and uses H & V pixel-shift for greater apparent sharpness but with no real improvement in limiting resolution and then and upsamples to a 1080L

frame buffer, then all output formats are derived from that. 1080 on an HVX is more a marketing gimmick than reality, or should I say not really closer to 1080 than it is to 720.

 

Read some of my articles on greeenscreen. They may help.

 

http://www.bluesky-web.com/broadcastvideoe...reenscreen.html

http://www.film-and-video.com/greenscreen2.htm

http://www.film-and-video.com/greenscreen-6.htm

http://www.bluesky-web.com/exteriorgreeenscreen.htm

 

and examples of how easy an HVX keys:

http://www.bluesky-web.com/HDVHVX.htm

Edited November 21, 2007 by WALTER GRAFF

[Scott Fritzshall]

Don't shoot out of focus. You are asking for trouble. You can easily defocus in post. While some myths about how difficult green screen is to deal with exist all over the web, it is really quite easy. If you need more help you can email me or call me.

Well it is easy to use a defocus filter in post, but the results can vary widely depending on what software you're using, and even with the best (at least regarding off-the-shelf software) you don't always get totally realistic results. I'd say it depends a bit on the content of the shot as well; if you've got really shallow focus on a person's face, for instance, and you want to rack, you're not going to get the natural look of the focus shifting along his face without quite a bit of work if you're doing it in post. It wouldn't hurt him to shoot it all in focus as a safety though.

 

Shooting in 1080p will offer you nothing noticable as the HVX shoots progressive frames in it's native resolution of 960x540 and uses H & V pixel-shift for greater apparent sharpness but with no real improvement in limiting resolution and then and upsamples to a 1080L

frame buffer, then all output formats are derived from that. 1080 on an HVX is more a marketing gimmick than reality, or should I say not really closer to 1080 than it is to 720.

You're totally right about that, and that was my usual recommendation. I completely forgot where I read that article because it explained the same thing but then also showed that it was allocating it greater bandwidth if you used 1080.

[Tim Terner]

Hi Daniel, I've found green to be better than blue for digital cameras. A cheapish software that has worked for me is Composite Lab Pro- here's a link to the lite version http://fxhome.com/compositelab/lite - I used this software to do a little test here http://blip.tv/file/361301/ - I found it much better than the built in keying options in Avid and Premiere Pro. Anyway, hope all goes well

[Walter Graff]

Well it is easy to use a defocus filter in post, but the results can vary widely depending on what software you're using, and even with the best (at least regarding off-the-shelf software) you don't always get totally realistic results. I'd say it depends a bit on the content of the shot as well; if you've got really shallow focus on a person's face, for instance, and you want to rack, you're not going to get the natural look of the focus shifting along his face without quite a bit of work if you're doing it in post. It wouldn't hurt him to shoot it all in focus as a safety though.

 

You're totally right about that, and that was my usual recommendation. I completely forgot where I read that article because it explained the same thing but then also showed that it was allocating it greater bandwidth if you used 1080.

 

When someone asks a question about a technique he isn't familiar with I always say take the easier step. No filter is perfect when it comes to creating a lens rack but FCP has some great filters for doing the same effect, but I say that too is not about the filter but the talent and experience in knowing how to use it. Given the two options, I'd tell a person newer to the chromakey experience that a post production filter will be a better option than shooting out of focus on a set, but then again I'd really have to know the exact shot and the desired effect to say whether it might be easier to do in post or as a key live. A simple rack can easily be keyed by someone familiar with the intricacies of keying.

 

Greater bandwidth means little when you don't need it. Having a five gallon bucket for two gallons of water gives you nothing but a bigger bucket with empty space. The HVX is a great prosumer camera, but it is not a full fledge HD camera so trying to find all sorts of headroom is not going to make for a better experience. It's like making a timeline 10 bit when the source is 8 bit. Sounds great but offers little in most all situations other than wasting more hard drive space.

 

As for green or blue, read my article on why sometimes blue is a better option for keying:

 

http://www.bluesky-web.com/greenscreen-6.htm

[Daniel Smith]

Thanks for the advice it has been very helpfull.

 

We will be using the Panasonic HD100 (DVCpro100)

 

For those of you remotely interested I've uploaded the script and storyboards (which took bloody ages)

http://homepage.ntlworld.com/bas/dalek/

[David Mullen ASC]

We will be using the Panasonic HD100 (DVCpro100)

 

Are you sure you don't mean the JVC HD100 HDV camera? Or the Panasonic HVX200?

[Mark Williams]

For those of you remotely interested I've uploaded the script and storyboards (which took bloody ages)

http://homepage.ntlworld.com/bas/dalek/

 

Hi Daniel looks like a lot of fun

 

Hers one I made earlier for something to do!

 

http://myspacetv.com/index.cfm?fuseaction=...ideoid=13684783

[Daniel Smith]

Are you sure you don't mean the JVC HD100 HDV camera? Or the Panasonic HVX200?

Oops sorry, I meant the Panasonic HD900.

[Daniel Smith]

Hi Daniel looks like a lot of fun

 

Hers one I made earlier for something to do!

 

http://myspacetv.com/index.cfm?fuseaction=...ideoid=13684783

That's pretty ace. Can I ask what equipment and software you used to do this?

 

Awesome work though. My project won't be quite on the same scale (I'm trying to keep things a minimal as possible, because I always get way ahead of myself)

 

Cheers.

Edited November 30, 2007 by Daniel Ashley-Smith

[Mark Williams]

That's pretty ace. Can I ask what equipment and software you used to do this?

 

Awesome work though. My project won't be quite on the same scale (I'm trying to keep things a minimal as possible, because I always get way ahead of myself)

 

Cheers.

Daniel Thanks!

 

Yes the film was made with a canon XM2/GL2. Edited in Vegas. Colour corrected, green screened, magic bulleted in After effects. Written by myself. Music was composed in Acid 3. I made the models in C4D version 8.5.

[Daniel Smith]

Just to confirm, the Panasonic HDX900 (HD version of the SDX900)

 

Daniel Thanks!

 

Yes the film was made with a canon XM2/GL2. Edited in Vegas. Colour corrected, green screened, magic bulleted in After effects. Written by myself. Music was composed in Acid 3. I made the models in C4D version 8.5.

Wow.. that was a pretty clean comp. Did you leave it all to after effects to remove the screen or did you have to manually remove some of it?

 

Awesome results considering the camera though. (no offence if that's your camera..but it's one of the best jobs I've seen done with a camera of that level)

 

I guess green screening is the best way to do it with video because of the sub-sampling, green is the only non sub-sampled colour. Unless it's 4:4:4 of course.

 

Trouble is I only have access to a bluescreen. (Pretty huge bluescreen though)

 

I've left a comment on the vid anyway.

[Mark Williams]

Just to confirm, the Panasonic HDX900 (HD version of the SDX900)

 

 

Wow.. that was a pretty clean comp. Did you leave it all to after effects to remove the screen or did you have to manually remove some of it?

 

Awesome results considering the camera though. (no offence if that's your camera..but it's one of the best jobs I've seen done with a camera of that level)

 

I guess green screening is the best way to do it with video because of the sub-sampling, green is the only non sub-sampled colour. Unless it's 4:4:4 of course.

 

Thanks Daniel. All done in AE! First of all I made a mask close to the subject then rendered this out. Then deinterlaced before finally keying out what was left. There are many tools in AE for getting a good key. The problem is often with the green/blue screen which has to be lit right and the actor to avoid spill from the screen. Since this I have bought some proper chroma key paint! AND upgraded the sound I'm waitng for a fostex FR2-LE to arrive and finally upgraded my DV camera! One of the hardest shots here was getting the Doctor into the arena with the camera tracking behind the perimeter bars.

[Tim Pipher]

Read some of my articles on greeenscreen. They may help.

 

http://www.bluesky-web.com/exteriorgreeenscreen.htm

 

Walter: I loaded and watched your outdoor blue screen pick-up segment from the infomercial -- it was indistinguishable from the original actual location scenes. Well done!

[Walter Graff]

Walter: I loaded and watched your outdoor blue screen pick-up segment from the infomercial -- it was indistinguishable from the original actual location scenes. Well done!

 

Thanks. I was under a tough deadline and delaing with about four other projects at the same time. Actually it could have been better. I could have Gaussian blurred her a slight bit more and raised the blacks on her shot to match better the environment she was put in with my back plate, along with a slight bit more edge softening on her. But I was under an deadline to get the updated infomercial on the air and it had to go to a closed caption house first so I made it workable and got it out fast. No one would really notice though. Only when I point it out and show the side by side do most folks see the difference. Other than that, it's done all the time and no one notices. If folks new how many times the shots of folks driving in cars were mattes (even ones that look incredibly real) they would not believe it.

[Daniel Smith]

Walter, I was just wondering about the part where you said about softening before keying. I also want to soften my look (added with the cinegamma it should look pretty awesome) but shouldn't I leave the camera settings on neutral, key and then soften?

[Walter Graff]

Walter, I was just wondering about the part where you said about softening before keying. I also want to soften my look (added with the cinegamma it should look pretty awesome) but shouldn't I leave the camera settings on neutral, key and then soften?

 

I don't think there is a perfect answer for this, only what works for you and with methods that you know how to use. Having a lot of experience with both keying, post and having been an Ultimatte operator in the past, I know what I can do both in camera and in post to make it all work for me. For instance if you think your edges are too sharp after you key you can use a mask cropping tool to soften the hi con that is the key making for better blends. BUt there are 100 ways to do teh same thing. I'd say spend some time with your mate and key filters and see what they all do and what they might do that you never knew could help make a better key.

[David Speed]

All very good advice.

Don't forget the three quarter backlight.

[Walter Graff]

All very good advice.

Don't forget the three quarter backlight.

 

Backlights are not necessarily necessary with doing vide blue screens if that is what you are referring to. There are a lot of notions about things one 'should' or 'must' do with backlights and keying. And most of these things are simply something someone must have written in a book a long time ago when things were in their infancy and folks simply believe it applies today. You want to light your talent not for the blue screen but for the artificial world you are putting him in with your backplate. That may or may not mean a backlight. That depends on the scene you are placing them in. With today's sophisticated software for cutting keys, the days of having to rim your talent with all sorts of light and the old wives tale of magenta light to counteract the screen are simply that. In an upcoming article in Scientific American on compositing I am quoted saying that today you can get a $30,000 matting studio in a $1200 piece of software. Of course like all the talk about cameras over content and talent, composting is not about anything as much as it is about understanding the process. I have a great DVD on doing keys in video and explore all the myths and show you that backlights need not exist, you can stand two feet from a properly lit screen and still key perfectly well and all sorts of other tricks from both a production and post production side as I take you on journey while I shoot direct and edit a real world commercial that is totally a composite. Regardless of whether you have seen it or not, keying in video is not as complicated as some might make it. I was recently faced with the ultimate potential problem shooting some behind the scenes of a fashion shoot. The studio was a cyc lit in pink that the talent stood in front of. I shot the video for the purpose of making it into a showroom piece. Then after all was done, the client said they wanted me to key the person over some backgrounds. I was never planning on it. All the talent was lit with was the 100 watt lamp the photographer used to focus, being a mere 10 feet from the background if that, which was lit with a single uneven 5k of pink light that raked the cyc. I used no additional light when I shot. And I shot with DV. And still I was able to key her out perfectly fine and make a piece that was never meant to be what it ended up being. The point is that keying today is so much more than how well you can light a screen (which is actually the easiest part of making quality keys in video), and really has a lot to do with learning about the post production perspective more than the production perspective, even if you are not a post person. If you are a cinematographer and know little about the post process of matting with video (chromakey), you are disserving yourself by not learning how it works and seeing it done. It will make your job 1000% easier if you really know what needs to happen (or what doesn't) to make things work including all the myths of backlight, etc.

[Guest Tim Partridge]

Walter,

 

David doesn't need anyone to speak for him, but with due respect, he was only making a suggestion regarding personal taste, not misleading anyone with a rule on technique (which is what you are implying). David has worked on some of the most important compositing movies shot over here.

 

Speaking of myths about keying/backlight, it isn't true that backlighting was always used pre-digital for bluescreen seperation as a rule. Check this out (DIAMONDS ARE FOREVER, 1971):

 

 

I remember reading what I believe was the 1983 CINEFANTASTIQUE review of RETURN OF THE JEDI, where they harshly criticised all of the backlit talent composites, declaring it an obvious old trick. So even pre-digital there were really no rules to lighting the perfect bluescreen figure, just preferences.