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Simple Green Screen Test Shot on Red

BradWright

BradWright

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This is a very basic green screen shot that I did today with the Red. I'm looking for some feedback on workflow. I processed this really quick and dirty by using RedCine to convert to ProRes HQ. Keyed in Motion using Veescope Key. There's a lot more noise in the dark hair than I was expecting. Anyone know if this could be related to the workflow?

http://web.mac.com/bradwright1/Site/RedGreenScreen.mp4
 
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Justin Kirchhoff said:
Under what conditions did you shoot for green screen? Lighting setup, resolution, etc.? I've done some tests and exported redlog dpx sequences. Flat images worked well for me so I can manipulate it more later.
Click to expand...

I shot with tungsten lighting and 4k resolution. The camera ISO was set to 500. The green screen was lit to about 40 IRE which may have been a bit on the low side. I used Veescope Live for shot visualization, pre-keying, scopes, etc.

Here's another example shot:

http://web.mac.com/bradwright1/Site/RedSunset.m4v

I reprocessed this shot using an R3D Quicktime proxy at half resolution. I loaded the file into FCP then sent it to motion for compositing. The problem that I noticed is the extreme amount of noise on the darker parts of the image. In this shot the hair on the right side has no noise. The hair on the right side and the top of the head has a lot of noise. Some parts of the shot key really well, but the parts with noise are really hard.

Is the noise due to the workflow or is it just baked into the shot?
 
Hi Brad,


1. Don't compensate Kelvin and ISO within RC or RA. Set Kelvin to 5.000 and ISO to 250. RC and RA induce a MUCH higher amaount of noise, especially in the blue channel when you try to make look things "right" by setting Kelvin to 3200 or even lower. If your screen does not look "right" green but more reddish don't worry. For the keyer it's still green.

2. Switch all sharpening off.

3. Don't use ProRes. It's a nice mid-end codec but not made for heavy post pro work. For a good key any compression artefacts are counter-productive. Use DPX or Tiff instead.

I don't know your key-tool and therefore cannot say anything bad or good about it but the industry is using mainly Keylight, Primatte, Ultimatte and Autodesk Diamondkeyer for some reason. I can acconplish with Red 4k green screen footage and Shake's tools (very basic Keylight and Primatte keyer) a lot and I'm not doing this for a living. Shake is currently 300 USD, still used widely and every penny worth.


Hans
 
Also don't rely on a program like Motion for compositing. It's great for graphics and title design but there are much more capable green screen compositors out there like Shake, Nuke, After Effects etc. This all around sounds like a worst=case scenario for keying that would have been rough with any camera. :)

Noah
 
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Hans von Sonntag said:
Hi Brad,


1. Don't compensate Kelvin and ISO within RC or RA. Set Kelvin to 5.000 and ISO to 250. RC and RA induce a MUCH higher amaount of noise, especially in the blue channel when you try to make look things "right" by setting Kelvin to 3200 or even lower. If your screen does not look "right" green but more reddish don't worry. For the keyer it's still green.

2. Switch all sharpening off.

3. Don't use ProRes. It's a nice mid-end codec but not made for heavy post pro work. For a good key any compression artefacts are counter-productive. Use DPX or Tiff instead.

Hans
Click to expand...

I've got Shake. The problem I was having was when I exported to 2k TIFF 16 bit and then imported into Color, the images were way off. The TiFF files looked okay in the Finder preview, but Color just screwed up reading the files. I tried DPX into Color, and it was able to read DPX correctly.

What workflow into Shake are you using?
 
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Hans von Sonntag said:
Export DPX from RA (250 ASA, 5.000 Kelvin) import into Shake. Do your composit, export DPX.

Hans
Click to expand...

I tried that and the footage was really reddish. I went through the workflow with shake and keylight. Unfortunately, although Shake offers greater control, but both Keylight and Primatte are really lacking. I can see reasonable amount improvement over this workflow.

There was a horrible gamma shift when converting from an image sequence back to a Quicktime movie in the Quicktime Player.

Here's the Shake composite which took hours to go through the workflow:

http://web.mac.com/bradwright1/Site/MauiShake.m4v

Motion version which took a few minutes to composite:

http://web.mac.com/bradwright1/Site/RedSunset.m4v

The Red just has a nasty amount of noise in the sensor. I probably underlit the green screen and the talent. However, I've shot plenty of green screen with my old Sony FX-1 HDV camera, and it has less sensor noise than the Red. It's a great camera, but it takes a lot light in order to get above the low level noise.
 
That bottle was a failure ;) These objects needs to be carefully keyed and processed.
 
I did a test too, and found that it really helps to put 1/2 CTB on either your lamps or on your lens. This is when using Tungsten lighting.
Furthermore, a bracketing exposure showed that the ideal ISO value is around 160-200, so essentially half the promised sensitivity.
At ISO 320 there is already a considerable amount of noise in mainly the blue channel.

Other than that, it is important to get your head around the FACT that you are dealing with a NATIVE 5000 K, RAW CAMERA!
It is similar to native daylight material in your FILM-camera: the ISO does not change, (unless you intentionally under or over develop) and neither does the color sensitivity.

Anything you do with REC709, Redspace, looks, color balance and ISO setting is just electronic "what-if" , it is metadata and the image file is unchanged.
So if you expose on ISO 500, use the wrong color of lighting and admit that the lighting is already low on this, you are in fact under-exposing two stops to start with, and any film or video camera will perform poorly.
 
BradWright said:
Unfortunately, although Shake offers greater control, but both Keylight and Primatte are really lacking. I can see reasonable amount improvement over this workflow.
Click to expand...

Sorry to hear that Shake's tool aren't working for you. I don't know how deep you are into keying but you probably know that most keys need more than just one key-node.

BradWright said:
There was a horrible gamma shift when converting from an image sequence back to a Quicktime movie in the Quicktime Player.
Click to expand...

If your go the DPX route without mixing with QT you'll be fine regarding gammashifts. QT is a poor container in this regard - pretty annoying. Welcome to Apple...

BradWright said:
Here's the Shake composite which took hours to go through the workflow:

http://web.mac.com/bradwright1/Site/MauiShake.m4v

Motion version which took a few minutes to composite:

http://web.mac.com/bradwright1/Site/RedSunset.m4v
Click to expand...

Both composits show a strong white outline around the subject in the front. I don't think that you wanted it like this. A seamless composit should be easily achieved.

If you have a short R3D to share I can have a look at it.


BradWright said:
The Red just has a nasty amount of noise in the sensor. I probably underlit the green screen and the talent. However, I've shot plenty of green screen with my old Sony FX-1 HDV camera, and it has less sensor noise than the Red. It's a great camera, but it takes a lot light in order to get above the low level noise.
Click to expand...

The RedOne is one of the best camerasystems on the market if we talk about GS work. If shot in 4K RAW it's on par with 35mm. Even the GS has been lit tungsten, like in your case, the result should be better than all the highend HD cameras like F900R can deliver when using their build-in tapedeck, let alone a video camera such as a Sony FX1 HDV...

Either you underexposed the screen badly or in your pipleline is something very wrong.

Hans
 
Artur Orzel said:
5 min with keylight AE
http://www.haasta.pl/pub/testy red/keylight.mov

shot on red 4k 16:9
lighting daylight
tiff 2k out from redcine sharpen 0, detail low downsample mitchell, colorspace redspace, gamma 709 ISO 250
Click to expand...

Good work! (but you missed to animate the focus pull in the background...) :)

That's how a key with waving hair should look like, plus no visible spill.

Hans
 
thanks Hans
there was no focus puller here when I was keying this shot ;)

It was very simple keying with no masks.
Usually when I do highend work I use at least two differend keys for hair and for body.

I found that there is no reason for keying 4k image. I don't see the difference between keying 2k scaled from 4k and keying 4k first than scaling to 2k or lower res. Sometimes I see better results with 2k

I don't know why people working with DPX. There is no need to use logarytmic when you are in linear world.
 
I got a bit further into compositing in Shake, and I've made some improvements. It doesn't look like it was the Red, as much as, that the backdrop was slightly under lit. After trying for hours, I just couldn't get Primatte pull a clean and Keylight had really grainy edges. I solved it through combining and mixing several keys. I might wind up porting Veescope Key to Shake, just because of issues like these.

Here's what I came up with after mixing the keys:

http://web.mac.com/bradwright1/Site/mauiSunsetShake.m4v

There's huge potential to create great effects shots in your living room with a Green Screen.
 
Jason Ing said:
what do you mean "missed"? what are you seeing? could you explain, please. thanks. :)
Click to expand...

The girls is walking towards the camera. Because she is always in focus the focus on the camera has been pulled. This focus pull is not animated in the background. For a perfect composition such things should be considered. Hence my remark about a missed focus pull.

But then it's all up to ones taste.

Hans
 
BradWright said:
I got a bit further into compositing in Shake, and I've made some improvements. It doesn't look like it was the Red, as much as, that the backdrop was slightly under lit. After trying for hours, I just couldn't get Primatte pull a clean and Keylight had really grainy edges. I solved it through combining and mixing several keys. I might wind up porting Veescope Key to Shake, just because of issues like these.

Here's what I came up with after mixing the keys:

http://web.mac.com/bradwright1/Site/mauiSunsetShake.m4v

There's huge potential to create great effects shots in your living room with a Green Screen.
Click to expand...


Hi Brad,

I took half an hour and had a short sneek into your footage.

Your footage is not too bad exposed, exposing a stop or two more to the right would have been better, using daylight even more. Nevertheless noise is not too bad.

Metadata were: 500 ASA, 2.800 Kelvin, Rec709. I changed that in RedAlert to 250 ASA, 5.000 Kelvin and RedLog. The goal for keying is to extract the least unprocessed footage as possible. The above mentioned specs meet the sensor best. RedLog keeps in a 10bit environment the whole information of the sensor without crushing whites and blacks, Rec709 is not a mistake though.

The girl has dark hair. The noisefloor lies in the dark parts of a picture. Because you shot the GS with tungsten the blue channel is obviously more stressed than in a daylight environment. Because the shot can be considered as underxposed the dark hair drifts even more into the noisefloor. Not the best foundation for a great key.

I did a quick and dirty comp with only two key-nodes. One for the GS and a second as a holdout matte for the foreground. I use the keymix node to assemble forground and background because forground, background and matte can be tackled seperately. For spill reduction I use SpillReplace, a very nice node that I can mail you if you want.

I always found that the right lighting to match the background is a vital part for a composition which the audience is buying without questions. Here I went a different way, I chose the right background for a given forground - doesn't make sense in real life though.

The key is not perfect at all. Reflections move through here eyes and the hair of the back of her head is still a bit fuzzy. In a fast cut film you probably would buy it, because location, subject and mood meet nicely. To make things perfect the movement of the background must be tracked, the data applied to the foreground and the XY data flattend to meet the parallax between the forground and background. Finally motionblur must be applied to the foreground. I skipped this...

What I did'nt skip is adding defocus, grain to the blurred background and colour correction.

The result:

http://hubbertvonsonntag.com/client/BradTest.mp4

The Shake script:

http://hubbertvonsonntag.com/client/BradTestShake.zip


Please bear in mind that I'm not a compositor by profession. There are many pros out there which would laugh at my result and achieve a considerably better result in 3 minutes. Compositing is an art. The beauty about Shake is the fact that the node-base approach might be difficult to learn from a beginners point of view but when you accomplished satisfying results you know much more about the laws of composition then those who use "one click" tools.

Hans
 
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