Greenscreen has green cast

[Björn Benckert]

Maybe the DP doesn't want to light for daylight and trust that in post the shot will be properly rebalanced to tungsten?

Impossible with preserved quality at times...


But yes if the lights are not to warm and the exposure is high the no problem... but thats not really the standard

Here is a project we did where we used no filter and since the exposer was even and good there is no real struggle, we also had green filtered lamps hitting the back wall.

bts:

with backgrounds:

and some other info:

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[Adam Eden]

The problem isn't with using tungsten lights on a key, I do that all of the time with out filters and i have never had a problem.

I think you have a similar problem to my Epic X.

For some reason ( and this started to happen about a year ago) my Epic X has a constant magenta tint to the image compared to my Epic M. So when i line them up together and perform an automatic white balance the X's tint goes to about -25 or towards the green to balance the camera out.

For example if i manually set the white balance of the Epic M 5450 Kelvins with the tint on 0 and the Epic X at 5450 the Epic X' s picture would look very magenta and so i would have to slide the tint to the green to about +24 and then both cameras would look ok.

On your supplied RCX file the picture is fine, but it tinted green, so if you go to the tint silder and type in -24 (putting more magenta in) then your image looks fine. I have spoken to RED about this and they wanted me to send the camera back in etc, but since i am in Australia and i use both cameras all of the time i found this impossible.

Adjusting the tint of the image doesn't affect the picture quality at all and from what i can see this will fix your problem. Just see if you are getting the same issue when shooting different subjects that are not on a green screen as my Epic X has a constant Magenta tint.

Hope this helps

 

[Björn Benckert]

The problem isn't with using tungsten lights on a key, I do that all of the time with out filters and i have never had a problem.

I think you have a similar problem to my Epic X.

For some reason ( and this started to happen about a year ago) my Epic X has a constant magenta tint to the image compared to my Epic M. So when i line them up together and perform an automatic white balance the X's tint goes to about -25 or towards the green to balance the camera out.

For example if i manually set the white balance of the Epic M 5450 Kelvins with the tint on 0 and the Epic X at 5450 the Epic X' s picture would look very magenta and so i would have to slide the tint to the green to about +24 and then both cameras would look ok.

On your supplied RCX file the picture is fine, but it tinted green, so if you go to the tint silder and type in -24 (putting more magenta in) then your image looks fine. I have spoken to RED about this and they wanted me to send the camera back in etc, but since i am in Australia and i use both cameras all of the time i found this impossible.

Adjusting the tint of the image doesn't affect the picture quality at all and from what i can see this will fix your problem. Just see if you are getting the same issue when shooting different subjects that are not on a green screen as my Epic X has a constant Magenta tint.

Hope this helps

Do not know what to say more about this discussion. But having noisy channels is no good for grading and it's no good for anything exept for those cases when you really want a noisy picture.

So what you are saying is that it works fine with having more noise than less. Maybe it does, but it does for sure not make keying better maybe good enough but I though the discussion was how to improve the shot.

The green in his shot does not have much green in it since it has a warm color cast over it. tinting that away might bring the skin tones back but the green is then getting pale. So again a filter would have done wonders, still that key is not a problematic one so no big problem there.

Best way to understand this, take a tungsten exposed frame with dark black and wide DR. look at the frame in RGB separately. Then you will see that the black and white frame representing your blue channel looks like dog shit. The green looks a bit better and the red looks fine. If you put a filter in and up your exposure to compensate for the filter then you will see that the green now looks much better, still not as good as your red as it never will, (as it's built into the debayer of Cmos.) So when doing chroma work noise is nice to be without using filter to balance tungsten light is a good way to reduce noise.

 

[Adam Eden]

Bjorn I didn't say anything like what you are claiming so stop starting FUD.

I was simply trying to offer some assistance to someone as one of my Epics has a constant magenta tint which is easily fixed in Redcine X.

I never have noisy images and i shoot both tungsten and daylight so i don't have a preference. I do how ever like to use big 10k tungsten lights on people through a lot of diff when on chroma key when shooting beauty shots, as a bigger source is a nicer light.

Im not going to argue with anyone about my thoughts as i was only trying to help a fellow red user.

I rarely go on REDUSER these days because if i ever offer advice there is always someone trying to start a fight if they don't agree with you.
Thanks Bjorn you have confirmed my belief that smart asses like you are still around here on Reduser and i probably wont ever offer any advice here again.

THIS IS WHY REDUSER SUX

 

[Björn Benckert]

Did not mean it to be like that so i shut up now.

 

[Eric Haase]

The problem isn't with using tungsten lights on a key, I do that all of the time with out filters and i have never had a problem.

I think you have a similar problem to my Epic X.

For some reason ( and this started to happen about a year ago) my Epic X has a constant magenta tint to the image compared to my Epic M. So when i line them up together and perform an automatic white balance the X's tint goes to about -25 or towards the green to balance the camera out.

For example if i manually set the white balance of the Epic M 5450 Kelvins with the tint on 0 and the Epic X at 5450 the Epic X' s picture would look very magenta and so i would have to slide the tint to the green to about +24 and then both cameras would look ok.

On your supplied RCX file the picture is fine, but it tinted green, so if you go to the tint silder and type in -24 (putting more magenta in) then your image looks fine. I have spoken to RED about this and they wanted me to send the camera back in etc, but since i am in Australia and i use both cameras all of the time i found this impossible.

Adjusting the tint of the image doesn't affect the picture quality at all and from what i can see this will fix your problem. Just see if you are getting the same issue when shooting different subjects that are not on a green screen as my Epic X has a constant Magenta tint.

Hope this helps

I have to say I have done many 2 camera Epic shoots and the sensors are always VERY different on each camera. With the same metadata settings, lens, and exposure the cameras always look notably different and require different color metadata settings to match. From what I understand making sensors involves some chemical processes and maybe there are not tight tolerances for variations..mostly because there doesn't NEED to be?? Whatever the reason, we can deal with the inconsistencies - to a point.

But it seems like if in this case you feel like you are not having a lot of green ambient spill/bounceback then you should definitely do a controlled experiment under measured color temps to determine your sensor's bias. If you have to adjust tint past -8 or +8 under 3200K 0M lighting to get a proper white balance I think you should send your camera in for service.

 

[Kalulu Ngilo]

I tried my best to key it into premiere. Some lousy results from me.

OK, I'm trying to figure something out here. We do a lot of greenscreen shoots with the EPIC rotated 90º. We recently rented out our camera to a very reputable camera/DIT/tech a couple weeks ago. Ever since it came back (or around that time) we have been fighting a greenish cast on our subjects when shooting green screen. OK, before you go on, here is the link for the r3d still.



http://www.creativeftp.com/_Odbe4Hb-2THF2R

We have our wall/floor painted digicomp green, she is about 15' away from the wall. The floor is coverd with packing blankets, as it is not head to toe. All lights are 3200k. The wall is lit by florecents, also at 32k. other lights are a combo of kinoflos and arri hot lights.

We have also shot with a blue drop that we hang in front of the green and light with the same cyc lights as the green, but don't have the color cast problem we do with the green.

I have done a full reset of the camera and is set for RC3 and RG3. When looking at our 17" panasonic SDI monitor, the green looks washed out. Its not very saturated as you see with your eye. This is monitoring with RC3 and RG3 turned on. RAW looks as to be expected, a little darker (shooting at ISO800) and flatter. Alhtough it seems that the green "pops" more when looking at RAW. Odd.

My question is, are we overlighting the green? The panny monitor we have for some reason won't play well with the EPIC and won't display the waveform. But that's another problem

I do have a dimmer pack and board available, and the flo's are dimmable, so I'm going to try to throttle back the green for the same amount of key, fill and greaser lights that the DP uses. I'm not the DP, I'm the tech, so I need to figure this out. What am i missing? I think we are just overlighting the green, but the the bossman disagrees and is trying to do the 80b filter and shoot at 56k in the camera trick. I know we should be using 56k lights when shooting green, but we rent our studio out alot and that wouldn't fly with 99% of the renters.

 

[Matt Gerard]

Wow, comig back to all this great discussion after the weekend, more than I'd hoped for! Lets see if I can summarize-

1) Camera had a full reset prior to this shoot, and it is the same green cast as before the reset. Tint settings were at default.

2) The green screen is large, its a 35' wide cyc behind her, I believe we have the floor covered , but the full back wall was exposed. Normally we have black drape curtains pulled to just outside of frame, but I wasn't in this shoot so I can't say for sure. I do agree that this is most likely light bounce wrapping around the subject, contaminating the skintones and such.

3) We did a test on another shoot a while back with an 80b on the lens and that did seem to hep quite a bit. I never though to look at the blue channel in RCX, I will do that for several of the shoots to see if the starved blue channel is a common problem.

4) I am intrigued with the idea that the 32k lights are actually canceling out some of the green from the green screen. When I get a chance I am going to do a test by shooting a subject with the lights at 32k, and then blue them and re-white balance and shoot again at 56k. From your comments I should get much better results with the 56k shot which makes sense, as it will be exposing the blue channel better.

5) We are able to pull keys from these shoots, so we aren't really worried about losing shots at all. We use Keylight in AE, and keying with a 4:4:4:4 prores export file from RCX is worlds better than trying to key a 4:2:2 8bit AVC100 filel from our P2 camera. Flyaway hair? No problem!

Its clear I have some work to do to tweak our lighting and studio into balance. My first job was to confirm that it wasn't something internal to the camera. Settings, tints, colors, etc. Since that has been taken out of the equation, time to focus on the lighting and setup.

I really appreciate all the different opinions and suggestions that you have taken the time to share. I will post more on the solutions we come up with as I solve them. Thanks again guys and gals!

 

[Adam Beck]

@Matt,

I ran into the same problem last week and freaked out about it. What was interesting was I was doing twelve testimonials with different skins tones. Obviously those would have a different result from one skin tone to another, but what I found interesting was that some takes were worse than others of the same set up and skin tone. I am not ruling out ambient noise and I believe that may be or at least have been a huge contributor to the problem.

@Adam,

Thanks for the insight man. Continue to participate on Reduser. I for one have said a few dickish things that I should not have said over something stupid.

 

[Adam Beck]

I've shot dozens of projects on green and blue screen with Epic under tungsten light. With the original sensor I used to worry about using blue filters etc. But now there is no reason you can't achieve great results under tungsten light on green or blue. The green screen projects that I've shot have ranged in size from a 20x20 green screen to over 120x40 green. There is always bound to be some ambient green on the skin, however subtle it may be. In your case it is extreme. It does look like ambient green spill as Phil mentioned. Maybe you should do the same setup and turn off all the lights lighting the green and see how much the skin tones change. Basically , shoot your subject under 3200 light properly exposed with a black background (maybe fly in a solid for this) and then the same foreground lighting WITH the green screen lights on. You'll be able to see how much the green cast is caused by sensor bias vs green spill.

Also, rate the camera as low an ASA as possible, while keeping highlights from blowing out. This will give you a fatter neg and it will be less noisy. 400 or 500 is much better than 800 for green/blue and typically on green screen there aren't a lot of tones above 3 stops over key so highlights usually aren't an issue.

examples on my online reel - Awkward promo, Big Bang Theory promos, DOve Magic Johnson and Virgin America (virtual sets).

After seeing your spots, I'd love to watch you shoot some green screen stuff. Your spots look great!