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  • Hey all, just changed over the backend after 15 years I figured time to give it a bit of an update, its probably gonna be a bit weird for most of you and i am sure there is a few bugs to work out but it should kinda work the same as before... hopefully :)

RED and bluescreen or greenscreen?

B

Barend Onneweer

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Hi,

This came up in another thread, but to keep that one clean I'll move the discussion here:

I said:
We'll be shooting RED on the 23rd and 24th of november. One day will be bluescreen.

I'd love to hook up an HDMI preview feed to a computer to do a live previz of the composite (using Livefeed and After Effects).

But of course this would only work when multiple simultaneous outputs are available, since I wouldn't want to deprive the cam-op of his viewfinder.

Any ETA on multiple simultaneous outputs? I should know better than to ask - but I'll try anyway
Click to expand...

And then Graeme responded:
Barend, I'd recommend green screen over blue screen if possible.
Click to expand...

I usually shoot greenscreen (I realize the advantages in chroma resolution) - but I'm considering blue this time because of the amount of spill expected. The floor is going to be glossy white... - a plastic ice skating material.

(http://xtraice.com/xtraice_en/home.html if anyone is interested)

Since the digital background will be mostly tints of blue I figured I'd avoid having to deal with ugly green spill. The blue spill would be less harmful. I realize that I'd be garbage masking a lot, but that's the deal with doing a chromakey shoot with a white floor.

Graeme, can I expect problems when shooting bluescreen over greenscreen? Another issue is that we'll be shooting windowed 2k for higher framerates - which compromises resolution even further.

We're finishing at 2k.

Bar3nd
 
I don't expect problems, I just expect green to give a better edge to the key. What I would therefore suggest is a test beforehand to see what things are like in reality. Silicon based sensors are less sensitive to the blue end of things, that's all.

Graeme
 
If you have the ability to test prior do so.

I've found that Blue screen +1/+2 stops (reflected) over foreground worked for one setup we did. Green same as foreground worked for the same setup.

I was able to key all the setups (-2/-1/0/+1/+2) but in terms of ease I found blue +1/+2, green on key worked for me (Flame2007).

Email me off list (flame @ imagesandsound . co . nz) and I'll arrange some dpx's for you to look test.

B
 
Raw recording and green screen and noise

Raw recording and green screen and noise

This is just something I've been curious about and relates to my limited understanding of RAW post processing, but since as I understand it, the files have "limited, less saturated" choma information. But using Redcine you crank the sat back up.

I guess my question is this, does all that extra chroma cranking in Post cause noise? Making things harder to key? I would suppose like with any CC, if the color information was there to begin with, then you're not really adding much noise, but if the chroma's being boosted from a smaller amount of chroma information, I would think it would. Am I misunderstanding something?
 
The camera captures a wide colour gamut with high precision. If you display a large colour gamut to a monitor with a small colour gamut, the end result is an unsaturated image. So actually, the camera records more colours, not less.

All cameras therefore have to increase colour saturation (in a matrix, usually) to get nice pleasing colours.

Graeme
 
Graeme Nattress said:
I don't expect problems, I just expect green to give a better edge to the key. What I would therefore suggest is a test beforehand to see what things are like in reality. Silicon based sensors are less sensitive to the blue end of things, that's all.

Graeme
Click to expand...

hi Gareme :
is this thing has some relation to color Bleeding issue ?
 
What color bleeding issue?

Graeme
 
when using very powerfull lighting sometimes you see that chroma color that have been used (geen or blue screen)reflects on actors faces or edges ,
i think greenscreen is much less color reflective comparing with blue
this issue is very clear in Graphics render .
 
Ah, that's "spill".

Green tends to give a better key as green is the major component of luma and a higher resolution than blue, and blue is inherently more noisy as silicon is less sensitive to blue light.

Graeme
 
Graeme Nattress said:
Ah, that's "spill".
Green tends to give a better key as green is the major component of luma and a higher resolution than blue, and blue is inherently more noisy as silicon is less sensitive to blue light.
Click to expand...

True. Although blond hair often keys better against a blue background and blue spill isn't half as ugly as green spill on human skin so usually when shooting greenscreen I need to add more spill suppression than on blue.

But given the choice 9 times out of 10 I'd go for green.

Barend
 
Hi,

we are building a studio what mostly should be used with Red. So the question is is there any kind of green what would word better than others? There are lots of choices like Rosco, EEFX etc and shades of green vary.
Anyone?

Thanks,
Janis
 
If your overlighting your greenscreen your just turning it into
a big green bounce board. Hence the spill factor.
A little over or under key exposure is fine, say one 1/2 stop.
Also depends on the green surface, some are more reflective
than others and need less light.
Mezmo
 
Hi j72,
There are a whole bunch of paints and materials now for green
work in my area, Asia/Pacific.
We use local products as the imported materials/fabrics, paints and
green gaffer tape tend to be overpriced.
Fabrics seem to be more reflective and need less light, which helps with the
whole process. They can also be draped over a cyc, stretched overhead or
molded to shapes. Some fabrics are thick and durable, also stretchy and can handle a fair amount of wear. I've not had to buy this stuff myself but apparently the trick is to source this material direct from the factory, as made to order frames can be very expensive.
Our stuff comes from China. From where ? Sorry can't help you here, local
suppliers keep this a secret. Not much help I know but try getting a swatch
of different materials available from suppliers in the E.U. then match it with
a similar factory supplied product if cost is a concern.
If your painting out large studio or cyc's in green that have to be painted back to white, white green white then green again, fabrics can perhaps save you money in paint and labour as they are reusable and quick to rig. They are also consistant in color density and
give a better result IMHO.
Hope this helps. Mezmo
 
Yes, definately helps.
Thank you Mezmo.
 
be a little bit careful with fabrics though that they aren't fuzzy. If they are too velvety you'll lose saturation at oblique angles as all you'll get is backlit white peach fuzz.
 
Hi Gavin,

thats actually the reason behind my questions. I've seen some fabrics in action but unfortunately not enough hours for proper experience on which ones to choose.

regards,
Janis
 
most cmos sensors have a somewhat higher amount of green photocells, and our testshots since nov indicate that red is no exception. if resolution is crucial, green might have an edge therefore.
 
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