6D: Chroma keying

[sgofferj]

Hi,

I'm starting to get gray hair over my attempts to greenscreen. No matter what I do and how I set the lighting, I always have mushy transitions between skin tones and the green screen, resulting in spill. I also tried different color profiles - Cinestyle giving the worst results. I also noticed a ton of noise in my image, although my scene is well lit on the border to being overexposed.
Is there something like high light noise? I'm currently shooting in 1080P high.

-S

[ansius]

just google around, spill is not something you fix in post but while setting up. Cinestyle does not always give you the best results, I use Marvels, they tend to work better on green screen and easier to color correct.

noise - check you settings, keep the ISO as low as you can, really this is priority #1, If you are using the ML, crank up the bitrate, it bight help, use ALL-I codec. And light the green screen correctly evenly, and bright enough! You have waveforms in ML and they help a lot to judge how well you have done.

learn to key the right way - videocopilot.net has some grate tutorials on that.

[sgofferj]

I did get the basics pretty much right. I just skipped describing them because I thought, it's a camera thing . But the bitrate I didn't try yet. The noise I even get with ISO100 and lights - well... 4x125W fluorescent (equivalent 4x625W halogen) softboxes SHOULD be enough for a 2x3m screen... I'll try the bitrate.

[LucianParaian]

If you`re shooting anything other than RAW, stop trying. You`ll never get good results with h264, because of the chroma subsampling, which is horrendous in compressed mp4!

The only way to go about shooting on green screen is raw.

[kihlbahkt]

Let me start by saying that if you are using Premiere Pro to key then LucianParaian's statement holds a lot of weight. While the compression in h.264 does provide challenges that one will not encounter if shooting Raw on green screen but if shooting h.264 and keying in AE then LucianParaian's statements simply are not true. Using keying and other effects and masks, with multiple layers in AE one can achieve excellent chroma keys from h.264 compressed video. If you only expect keylight or other software to pull an excellent key with one click of the eyedropper then yes, h.264 footage will not key to anyone's liking. youtube, lynda (pay site) or other online resources can provide instruction. I found a video on youtube that had a great workflow and if I can locate it I will update this post with a link. Dont be discouraged, you can key this footage but you may need to invest time learning how to pull keys from h.264 video. I am currently in process of working with many clips shot on green screen and without research and education on how to achieve the results I want, it would have been a failure. I had to take the time to find out what will work best. The are many different workflows to get to the end result. None of them are simple but you should be able to pull together a workflow for yourself.

[Levas]

How is your white balance setting in camera, are you using a grey card or some other tool to get perfect white balance in camera ?
If you're not shooting raw, your white balance must be perfect for chroma keying.

[sgofferj]

I'm using KDEnLive for keying, specifically, the color select effect (not the bluescreen effect - that sucks).

I do manual white balance with a grey card before every shot (if the light has changed) as a matter of principle.

I think, I found the reason for the noises. My wall has a structured wallpaper which creates massive aliasing on the distance I shoot and pretty much the same goes for my backdrop. I get much better results when I have a huge distance to the backdrop and I shoot wide open, so the backdrop is totally blurred.

Also, the h.264 theory obviously has some merit. On closer view, I see compression artifacts on the contrast lines between skin tones and the backdrop. Unfortunately, I still didn't manage to get a working RAW workflow together on my machine (Ubuntu 14.04).

But after shooting my documentary in Germany, it's already pretty clear to me that I need another camera. The 6D makes great photos but for my style of film shooting it just doesn't work . I do "news", documentaries, interviews and such and a lot run'n'gun. I need MUCH better lowlight performance and autofocus would be useful. So - the whole decision process again - but this time without the requirement for stills. Maybe a C100 with a Ninja Blade? Is there a recommendable more general forum, English or German? I think, I'll probably a bit offtopic with that here .

[kihlbahkt]

Not familiar with KDEnLive. Here are some simple steps that might help, but I use Adobe so I have no idea how one would pull this off in your software.
Generic workflow...
color correct to bump up green channel saturation before key. way up.
Use garbage mattes to reduce the areas that need to be keyed
add Key effect and adjust key properties. if you have alternate views other than final, use them to help define white, grey, and black areas.
Pull a mask or track matte from that key mask
Blur/feather masks
Apply the mask/matte to the movie to isolate  the subject..so you'll need to delete that original effect after you generate the mask/matte
You may need to use more than one instance of the key effect prior to or even after mask/matte is applied to deal with spill and fringing.
You may even  need multiple masks/mattes to get the result you want.
Good Luck

[Kharak]

If Chroma Keying with h.264, in my experience, the recording work has to be done almost perfectly in order to get good results.

First of all, I would like to mention that Cinestyle can be your downfall in this matter. If you are chroma keying with cinestyle, the scene might simply be too flat for your software to be able to exclude the green screen. Same goes for landscapes and cinestyle, if there is no contrast in a scene and you record with cinestyle, you risk ruining the footage as it will be hard to pull back all the details that differentiate in contrasts.

Do what kihlbahkt said, bump up the green channel and if possible in your software, start a new layer after for further adjustments.

2nd: Filming a green screen.

Its imperative that you keep some distance between your talent and the greenscreen to avoid green reflective spill on your talents hair, shoulders etc. Atleast 3-4 meters when the greenscreen is lit up by controlled light.


And with h264 its very important that your greenscreen is evenly lit as the codec is so compressed that small variations in lighting can easily make artifacts that can require masking to remove, which is a pain when it could have been avoided.


and last.. Try doing this in RAW and save your self a headache

Good luck! 

[sgofferj]

I finally figured out what the problem is... It's the gross aliasing and moiré of the 6D. I usually have a 3-day-beard and in all test shots I have been wearing a t-shirt. My backdrop has some slight pattern and so have my walls. Especially my beard and the hair on my arms cause insane aliasing and moiré which leads to totally mushy ruined separation between me and the backdrop.
I have been shooting outside a few times in the meanwhile and under real world conditions, the 6D actually produces very nice quality footage.
Here's a news report I shot, h.264, C-log, right out of cam, no post except cutting:

https://www.youtube.com/watch?v=9pJVSo3HQAI

Besides, I discovered the false-color/greenscreen option in ML. COOOOOOL stuff! Helps A LOT!!!