>Greenscreen and Bluescreen Checklist

>Shooting for greenscreen or bluescreen? Here’s a list of hard-earned experiences from the shoots where I’ve been vfx supervisor. I don’t claim to be a chroma expert, so please post a comment if you have more tips to add to the list!

UPDATE: I’ve added some info on depth-of-field and motion blur as point number 2.

1. Keep it Blurry in Camera
Turn off all in-camera sharpening! This might make your director of photography (DOP) nervous and it will certainly make it harder for her/him to focus. On Sony cameras, there’s usually two settings that need to be turned off: Detail and Skin Detail.

By default, all cameras apply a sharpening filter as a post-process before each frame is committed to tape/disk/memory card. While this makes the image look better, it is makes it so much more difficult to get a good and clean edge between your foreground and your chroma screen. Digital sharpening works by finding adjacent pixels of different lightness values and then increasing the difference, in effect crating a border with much higher contrast. Notice also how the in-camera sharpening brings out noise and imperfections in the chroma screen.

So shoot without sharpening and add it in post instead!

2. Keep it Sharp on Stage
While you don’t want the camera to add artificial sharpening, you still want to keep everything in the foreground as sharp and correctly focused as you can. If the chroma screen is blurred in the background will only help to make it more evenly lit and textured, but you want to avoid having to key out blurred foreground, trying to separate it from the chroma.

If the blur comes from a too slow shutter speed or by too narrow depth-of-field, you’ll have to tweak the keyer and possible sacrifice other parts just to manage the fuzzy edges. A blurred edge between foreground and background means that you will have to compromise between the edge and despilling settings, and quite possibly have to keyframe these settings to compensate for different levels of blur on different parts of the clip.

Instead, add motion blur in post by using optical flow technologies such as ReelSmart Motion Blur and add depth-of-field by layering chroma clips and post-blurring them.

3. Resolution and Framing
You want to shoot with as high resolution as you can afford, to make sure you keep your options open when you get to postproduction. Even if your finishing in SD, try to capture in HD or even 16 mm or 35 mm film. The more detail you can capture, the cleaner key you’ll be able to pull. You can always scale down, but you can’t get back image data that you haven’t captured…

Keep a constant lookout for how the DOP frames the action. Since you’ll be working with the shots in post, you can disregard the safe areas that are normally cut off by monitors and TV sets – that’s 10% more image data to use!

I’ve found that I often have to keep pushing for tighter framing of each and every shot. To make sure that you and the DOP sees the entire image, set the camera viewfinder and the preview monitors so they are underscanned.

Even if you’re shooting for a 16:9 production, you’ll most likely want the set the camera for 4:3 aspect ratio, unless your shooting something that will fill the entire frame horizontally. Otherwise you’ll be sacrificing horizontal resolution, making for rougher key edges.

Another way to squeeze the maximum amount of resolution from your cameras is to tilt them 90 degrees for shots of standing people.

Here’s an example of three Sony Digibeta cameras with two of them tilted 90 degrees to capture standing people at maximum resolution.

4. Blue or Green?
What you are trying to achieve is to provide your keyer with a color channel that is as distinct as possible. Since human skin tones and lips tend to be red, that leaves blue and green. So which one to choose? That depends on a couple of things…

Green chroma screens have become more and more popular in recent years, largely because green provides a brighter color channel that tends to have less noise than the blue channel. The relative brightness of green makes it a bad choice for shooting blonde hair though, which is a lot easier to key against blue backgrounds.

The bluescreen has some distinct advantages. When you can’t avoid a lot of spill (for example when you have to put the foreground very close to the chroma material) you can take advantage of the fact that we tend to find blue casts less disturbing than people walking around looking sea-sick with green faces. Also, when shooting for something that will be composited on to outdoor backgrounds and water, a slight blueish cast won’t be a problem.

So if you are shooting a blonde with jeans, you’ll have to settle for a compromise!

5. Don’t Depend on the Crews’ Imagination
Good storyboards that can be shown to the entire crew, both before the shoot (so that they can bring the correct gear) and during the shoot. Depending on the complexity of the shot you might need animatics, but at least bring sketches or printouts.

Talk to the crew so that they understand how stuff will be used in
post. For example, I have had instances where cameramen have cut off
talents’ feet even though I’ve tried to explain that we needed the
whole body.

6. Don’t Depend on the Talent’s Imagination
If talents are supposed to look at things that will be added in post, make sure they have something (that can be keyed out later) to look at and interact with during the shoot.

7. Get Good Clothes
Make sure you avoid greens, browns and khaki for greenscreen shoots and jeans and other blue clothes for bluescreens. This cannot be allowed to be something you decide on location, it must be planned beforehand.

8. Get Good Props
Make sure you can dull-down shiny stuff so that they don’t reflect the chroma color.

The choice of a shiny metal briefcase in the example above is a particularly bad one, considering it had to be rotoscoped in all the shots. The ear-ring was taken care of with an Inside Mask in Keylight.

9. Match the Lighting As If Your Sleep Depends On It
There’s no substitute for good lighting and gaffers that can match foreground and background. You can fix almost anything in post-production, be relighting is among the hardest and least successful things you want to spend your nights with. There’s nothing that screams fake as much as wrong lighting!

10. Preview Directly On Set
You can’t underestimate the value of being able to compare a roughly keyed-out foreground against the background that it will be composited against. Not only is the immediate feedback important for the talent, it is also invaluable when it comes to matching the lighting and perspectives.

If you can’t use a real-time keyer with a feed from the camera, like in the image above, at least bring a laptop and a digital still camera and do a quick key until the lighting matches perfectly.

11. Go Easy on the Tracking Markers
If you use tracking markers, make sure you have sufficient number in each shot, without having too many that you will have to paint-out in post. Try using markers with almost the same color as the screen, for example by using chroma tape, so that you can remove them by a second keying-pass.

The extensive number of markers in the example above comes from the fact that they were to be used for a tight head-shot during a 30 minute interview where the subject didn’t want anyone except the interviewer and the DOP present. Therefore we had to make sure we had at least some markers visible at all times.

12. Avoid Unnecessary Spill
Keep the foreground as far away from the chroma screens as possible, since you’ll have less spill to deal with. Make sure that all parts of the floor that might reflect chroma color onto the foreground are covered by non-reflective material such as black cloth.

It’s up to you to keep each setup as far away from the chroma screen as possible, as people seem to be attracted to the big wall of color. It is your job to check that the entire foreground has chroma behind it during the entire take, which is why rehearsal is so important since it gives you the chance to spot potential problems which will force a setup adjustment.

13. Keep It Clean
Strive to keep the chromascreen as spotless as possible, and stop people from walking on it unnecessarily.

14. Get to Know Chroma Sampling and Codecs
Since chroma keying works on the principle of isolating one color, you would think that it was extremely important to get as much color data from the camera as possible. This is unfortunately not the case in many circumstances, especially when it comes to video. I won’t get to geeky here, but you need to understand how digital video is stored.

The human eye is much more sensitive to the luminance/lightness of what we see, than to the color of the world around us. That’s why all (but a few super-high-end cameras and formats) immediately throw away at least half of the color information that is captured. This is bad news for keying, since the less color information you have, the harder it is to accurately isolate a color.

If at all possible, you want to capture a 4:4:4 image without any color compression, and then keep that color resolution intact by using an appropriate codec at least until you have passed the keying stage. You should also strive to retain the more than 8 bits per channel of data that many systems capture, such as the 10-bit color depth of DigiBeta.

Trying to key of DV footage is even harder, since the DV codec only stores a quarter of the color data, using a 4:1:1 compression. If you have no choice but to key from DV footage, try to blur the U and V channels before pulling a key, or use a keyer that does this automatically, such as dvMatte from dvGarage.

Here’s an example of the low horizontal color resolution of DV footage:

15. Frames Rather than Fields
Try to shoot progressive rather than interlaced, to avoid having to de-interlace the footage. If possible; shoot double the frame rate with progressive if you need to go to interlaced later. Avoiding interlacing not only gives you a cleaner edge and saves time on de-interlacing, but it also provides you twice the spatial resolution which might come in handy if you have to up-res in post.

Interlacing is an evil compression technique that severly limits your options, and you should always try to avoid it, instead adding it at final output.

16. BYOC: Bring Your Own Camera
Take lots of reference shots of locations, the lighting setup and other stuff that will help when you crawl back into your dark post-dungeon. You can never have too many reference shots!

Final Words
Avoid the temptation to think that problems on set can be “fixed in post.” Everything that can be done in front of the camera should be done on set. Make sure the time allocated for postproduction is used to enhance the final outcome instead of fixing mistakes done when shooting.

Also, be prepared to pull several keys and to use garbage mattes and core mattes. Remember; you are trying to extract the edges, everything else can be mattes/roto’ed!

- Jonas

46 Responses to >Greenscreen and Bluescreen Checklist

  1. Anonymous

    >Nice tips.
    The question I’ve always had is do you want to use shallow depth of field when shooting to make the greenscreen blurry, or is it easier to key when it’s sharp?

  2. Patrick

    >One of the cool things about chromakey work, if you only have one of those 1/3″ CCD cameras, is you can easily blur the background you key in a bit in post- which kind of makes your cheap cam shot look like it was done on film. And rack focus in post? No problemo. I love chroma key.

  3. Adde

    >Cool. Thanks for sharing this.
    Adde.

  4. Anonymous

    >In order to diminish spill you can use light coming from above the talents. Use magenta gels for greenscreen and yellow for blue, because those are the respective complementary colors.

    And yes, it is a good idea to use shallow depth of field in order to blur the screen, better than do it in post.

    If you shoot quick moving talents or objects, use high speed shutter, not 1/50 or 1/60, because the blur will blend foreground and color screen.

    Pay attention to the workflow. If you shoot interlaced DV: deinterlace it (you can also deartifact it – ie with Magic Bullet-, that makes a noticeable difference). If you make an intermediate file dont save it as DV again. Save it as an uncompressed format, as avi uncompressed or the free losless huffyuv codec.

    In order to achieve a uniform color screen lighting, if you dont have a photometer, use the camera zebra pattern. If the screen is very uniform lit, the zebra will appear or disappear only with one “click” of iris aperture.

    Hair: can you imagine Superman with a tangled hair. How complex would have been to key it!

    Ignacio Simon
    http://www.simonfilm.com

  5. Stephen Gagne

    >Ignacio,

    Great info here. Thanks for putting this together.

    Have you done any tests of greenscreen optimal brightness? On a recent shoot I tried lighting the greenscreen at 40, 50 and 60 IRE, and found best keying of blonde and grey/white hair at 40 IRE. Even though I had solid, soft foreground lighting and straw kickers, the natural partial transparancy of blond and gray hair seemed to otherwise allow more background green into the hair strands when the background was brighter than 40.

    Subject faces were lit with highlights at 70 IRE, which resulted in light hair colors having highlights higher than that of course, sometimes nudging 100 — and base skin IRE tended to be 50-60 on key side of face, and 30-40 on fill side.)

    Your comment that blue screen works better with blonde hair makes sense to me, and makes me think maybe I should move to blue for my next cyc shoot. We deal with all hair colors, and my lead has grey hair. Until now, the only stuff I’d read on this said that green was better for video cameras and blue was better for film. I’ll be shooting Panny HVX200s at 720p24p.

    Thoughts?

    Thanks,

  6. Anonymous

    >Thanks for sharing this!!!

  7. Motionworks

    >Superb information Jonas.
    JD

  8. Jonas Hummelstrand

    >Thanks for all the comments!

    I didn’t put anything in the original post about the relative brightness of the foreground and the chroma screen, because I’ve never found any conclusive info.

    People seem to have different opinions, and the exposure would be dependent on the type of chroma color (not just blue/green, but also different hues of the same color.)

    In practicality, the uneven exposure of the chroma screen has never given me any problems with Keylight. I find that on a budget shoot, too much is going on for me to stop the circus just to demand an adjustment to the chroma screen.

    The important things to look out for is the tendency for the action to get too close to the screen, plus checking that the lighting matches to background. If you’ve managed to get all that nailed, by all means you can get better results by fiddling with the chroma screen lighting, but in worst case you can fix unevenness by doing two keying passes.

    I read a tip on AE-list that you can use a cheap mobile phone camera to check the evenness of the chroma, since its preview is of such a low quality that you can spot differences by looking at the banding on the display.

    Concerning depth-of-field, I haven’t had any hands-on experience with keying really blurred parts of a footage, but my guess would be that it would be easier to key sharp edges, as the keyer otherwise will have to determine what is actual chroma colored background and what is spill on the foreground that should be removed with spill supression. So if possible the chroma screen can of course be blurred, but I would try to keep the entire foreground in focus. The same goes for motion blur as Ignacio pointed out in his comment. Use a higher shutter speed and then add motion blur in post with an optical flow technology such as Revision Effects’ ReelSmart Motion Blur.

    I’ll look for some motion blurred footage and I think I’ll add to the original post.

    To light the foreground with backlight of a complimentary color to the chroma is and old technique, but with today’s keyers with spill supression, I find this backlight screams “chroma” on the finished composite. If it is subtle, it might work, but keep those lights low.

  9. Luke

    >There is even use of Magenta screens now. its all relative to the colors needed in the foreground etc.

    Major movie using magenta screens… well the matrix.

  10. Anonymous

    >Some exellent tips, but do you use a certain program or do you have any prefrences. I am using Final Cut Express2. It is a bit limited, but I have had difficulties in keying out all of the greenscreen areas.
    I will embrace your tips next time I am trying to use these features.

    • If you want to key I would get the free trial of adobe premiere pro Cs5.5 and see how you like it. Otherwise look into plug-ins that will work with your software. After Effects would be an ultimate add-on for what you are doing but the new keyer (ultrakey) in Premiere Pro is much easier to use.
      This post addressed many issues that are relevant to the professional- but I would add some suggestions for amateurs who are just starting out:

      Computer power is everything when it comes to editing your footage. The single best thing you can do is put your assets on different hard drives and connect them in the fastest possible way (eSATA)- These can be external-but will save your computer a ton of work. Put your Key footage on one, the background on another and the file information on a third (this one can be slower like USB) and then a fourth one to write to. Running the application on your computer is the fifth one. You will be surprised at the shortened rendering times and the ability to watch your footage while you key in the background (on a fast enough computer.)

  11. André Hedetoft

    >Wow!

    Insanely great article!

    Just wanted to stop by and say thank you for putting this together!

    And regarding Anonymous last comment:

    I would recommend using After Effects or something like it to do your color keying. But otherwise here is a great tutorial on greenscreen keying in Final Cut:

    http://www.kenstone.net/fcp_homepage/chroma_key_fcp_hd_monahan.html

    André Hedetoft
    Geek Movie Director
    Join my Fan Club so that I get to make my next movie over at http://www.andrehedetoft.com

  12. Anonymous

    >thanks for sharing this info. it’s been very useful.

  13. Anonymous

    >With sharpening, is the zero setting no sharpenning or do you have to go as negative as your settings go?
    All the sharpening settings I have seen go into the negative.

    Tony

  14. Jonas Hummelstrand

    >Tony,

    As in-camera sharpening is a process that the camera applies to the frame before committing it to tape/disk/memory, having negative sharpening sounds strange (more like blurring.) I’m afraid the only way to find out is to look in the manual or even better; put the camera on a tripod and shoot the same motif with the different settings and look at the frames up close (like the first image in the blog post.)

  15. Anonymous

    >Hi, Great artical.

    Any idea where I can get stock library of people, walkings, chating, lying down, having drinks etc.

    I would like to try some composition techniques and to not have the facility to setup a green screen studio.

    Guy

  16. simply sner

    >Hi! Thx for sharing this great article!
    Some friends and I are building our own greenscreen for some smaller projects. Now we are going to paint it and I was wondering if there are recommended (RGB-)values?

  17. Jonas Hummelstrand

    >I doubt you’ll be able to give the shop RGB values, but if you could you’d want R0 G255 B0.

    The best is of course dedicated greenscreen paint (expensive) but if you’re on a budget you want to go for something that will contain as little non-green as possible, which is hard to measure until you’ve already painted and lit the screen and shot it with you camera of choice.

    Try to get samples and test, that’s the best way to go.

  18. directorGeoff

    >Jonas –

    Proper greenscreen pain is very expensive (about $50-$60 per gallon here in L.A.) If you can find something that has already been painted chroma green (or chroma blue) or can find a tiny strip of ACTUAL greenscreen cloth, take it down to any decent paint store and ask them to color match it. All large hardware stores can do this. Good luck & watch out for corners and seams!!

    - Geoff

  19. Jonas Hummelstrand

    >Geoff,

    Great tip, and remember to non-shiny paint!

  20. MichielEbberink

    >thanks for sharing

  21. Todd_Kopriva

    >I’ve added a link to this wonderful page from the “Keying overview and tips” section of After Effects Help on the Web:

    http://livedocs.adobe.com/en_US/AfterEffects/8.0/WS3878526689cb91655866c1103906c6dea-7bfd.html

  22. Jonas Hummelstrand

    >Thanks Todd!

    Stay tuned for the video tutorial version of this post, coming “really soon now.”

  23. Metta

    >Fabulous article.
    Concise, informative, well written.
    Move over 10 Minute Film School – Here’s chroma-key in 3!
    WOW

  24. grumula

    >I just got the materials to set up a bluescreen yesterday, then I Stumbleupon this article, great words of advice, thanks for the post mate!

  25. Anonymous

    >HELP NEEDED.

    I have to shoot a basket player in action on chroma key.
    I’m very worried to balance correctly the shutter speed in order to have clean images with motion blur (increasing shutter speed) but avoiding a strobo effect due to a too high shutter speed.
    Is anyone experienced in this?
    I’ll shoot in HDV progressive, which would be the best shutter spped to avoid motion blurs AND strobo effect?

    Thanks

  26. Anonymous

    >Sorry typo on previous post
    “… in order to have clean images WITHOUT motion blur…” (of course)

  27. Jonas Hummelstrand

    >I’m afraid this is a classical case of “either or.” The motion blur helps the brain perceive a motion as smooth, so without motion blur you’ll get “strobing” in parts of the picture that has more movement. (See “Saving Private Ryan” for an example of this look.)

    For green screen this motion blur makes it harder to key, but you’ll still want motion blur in the final shot, so how to get both, you ask? One way is to shoot with higher shutter speed and then add motion blur in post via a optical flow-based motion blur system, such as “ReelSmart Motion Blur” from revisionfx.com

  28. Anonymous

    >cool!
    i'm no pro – i make videos of my sibings – and i searched some tips – these are so easy to modify to my camera and movie maker type! i can ignore half the tips since they have no relevance to my projects but the others make my videos better than the REAL videos we watch.

    thanks sooo much!

  29. Geoff Boyle

    >Great page, if only some of my clients had read it in the past 30 years!!

    As far as levels go I try to keep the screen at around 50%, this is what it was for Mutant Chronicles and Dark Country and worked well.

    Geoff Boyle
    http://www.gboyle.co.uk

  30. Anonymous

    >Think as if all you can do is remove the green or blue… nothing else

  31. Taiwan

    >Amazing… Should make my green screen better!

  32. lou

    >Hi, thanks for the advice, I want to shoot a short film which relies heavily on shadows and spot lighting. I wanted to ask how i should approach this when lighting the green screen. should i light bright and add spots and shadows in post or risk the shadowing on greenscreen? thanks.

  33. Jonas Hummelstrand

    >lou,

    Always strive to totally separate the lighting of the foreground and the greenscreen. This becomes tricky when you need to shoot the foreground touching the greenscreen, as when you need to see an actors feet. However, remember that all the greenscreen you are concerned with is a few pixels outside the foreground. The rest you can easily rotoscope out with a "garbage mask."

  34. littlegems

    >I was wondering if shooting greenscreen can work on shooting talent that is wearing tulle which can be a little see through around the edges…thus possibly making it harder to separate later…what to do in a situation like that?

  35. Jonas Hummelstrand

    >littlegems,

    Can it be done? -Sure!
    Can it go wrong? -Most likely.
    Should you do it? -Do you have enough experience to anticipate the problems so you can minimize them?

    If all things are optimal (lighting, exposure, recording resolution and compression, color subsampling) then it might work, but be aware that you are creating a situation that will possibly create problems, artifact or even cause the footage to be unusable…

  36. Anonymous

    >this is some amazing stuff thanks a lot for the elightenment.

  37. Sean Green

    >These are great tips everyone should follow to make all their green screen productions jus that much better. Thank you for sharing.

  38. The Greenery Studio

    >So far this is the best checking of green screen tips we've been able to find online.

    Are you still coming up with your video version? If so, we'd love to add it to our blog.

  39. Anonymous

    >Hi one if my clients is having problems keying some footage I shot. I am experienced at lighting green screen through many tears of trial and error so I know the lighting was good.
    I used a Sony HD 900 (which I know is a little old now) with the Detail setting turned off. I have only had positive feedback about this in the past. Could this be adding to the problem?
    They say it grainy when trying to add Sharpening?
    Any advice or suggestions appreciated!
    Thanks so much
    Hope to hear from you soon

  40. markus ziegler

    >Thank you very much for your findings.
    I am working a little in chromakeying, and it is hard for me to think of everything.
    Now it is way mor easy…
    Markus

  41. Alberto

    >Very insightful. I am pretty new at this and am looking to get a good video camera for chroma key filming for around $500. What should I look for in a video camera? Is it the video camera or the software that primarily affects the quality?

    Thank you!

  42. I’m a teacher in a Bristol (UK) primary school and have set-up a very simple recording studio in an old cupboard for the children to play around with simple blue-screen work.

    We are using (very) cheap equipment and free software so the quality isn’t great as you would imagine. However, it’s great fun for the kids to perform work and then change the background behind them; for example we recently wrote, read out and videoed space poems and the kids inserted suitable space images behind themselves.

    The tips on this page have helped us improve the quality, even with the equipment we’re using and the kids were impressed, so a big thanks from me/us!!!

  43. great tips, this is going to help me a lot with my shoot thank you

  44. Best article I’ve found for this, by the way.

    I’m having difficulty shooting grand piano (unfortunately high gloss) against greenscreen. Original video seems fine; trouble enters in chromokeying stage – lots of horizontal “noise”. Wondering what is MOST LIKELY causing the problem: Sony Handicam recorder, Pinnacle Studio Plus software, subject too close to green screen? I know it’s tough to diagnose something you don’t see, but I don’t want to go buy a new camera if the software is the issue, etc. Any help will be greatly appreciated.
    Thanks,
    Michael

    • Jonas Hummelstrand

      If you’re getting noise, that points to a problem that’s caused by the camera and/or lack of lighting. I can’t comment on Pinnacle Studio Plus software, but I can tell you that it’s not considered a professional tool.
      Shooting high-gloss subjects can be made less of a pain if you can position it so it doesn’t reflect green back towards the camera. Remember that you only need a few pixels of green around the foreground you are trying to isolate, there’s no need to fill the entire screen with green!