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Steve in Pudsey7,948 posts since 4 Jan 2003
Yorkshire Look North (Yorkshire)
The Euro 2016 bit looks good. The sort of thing you could imagine being done in A at NBH but the rectangular sport section looks out of place when news and sport news is circular now.


They used a curved VR set last night (with Julian O'Neill reporting) to illustrate some of the main headlines from the budget. I suspect we'll be seeing much more of this particular VR set.

Not quite sure why they've opted for the rectangular arrangement for the sports segment. And unfortunately the presenter's close proximity to the physical green sheeting is only exacerbating the green reflection on their face and clothes.

Technical question: is there any particular (technical) reason why bright green is the preferred colour for CSO/VR sets? Red would've been a good alternative, given the amount of red also present in the real and virtual sets. A slight red reflection on the main set from the VR section of the studio wouldn't look quite as out of place.


Red is too close to skin tones. I think there is also a technicial reason for using green in the digital domain.
Write that down in your copybook now.
Bail3,442 posts since 30 Mar 2001 Moderator
Meridian (South) South Today
Exactly, there are two other reasons why cameras "see" green better than any other colour, the first is the sensor itself single sensor cameras / CMOS chips have tightly packed Red, Green and Blue photo diodes, the alignment of which gives a slightly higher number of Green senors to any other, see image:

*

The second sensor type, CCD uses 3 separate sensors for Red, Green and Blue, and uses a prism to separate the colours. This time greens place right in the middle of the visible light spectrum makes it the best colour to be received in this setup and thus the best to key with.

Further reading: http://www.techradar.com/news/video/the-science-behind-green-screen-1301075
Bail.
1
denton887 posts since 4 Jan 2003
The Euro 2016 bit looks good. The sort of thing you could imagine being done in A at NBH but the rectangular sport section looks out of place when news and sport news is circular now.


They used a curved VR set last night (with Julian O'Neill reporting) to illustrate some of the main headlines from the budget. I suspect we'll be seeing much more of this particular VR set.

Not quite sure why they've opted for the rectangular arrangement for the sports segment. And unfortunately the presenter's close proximity to the physical green sheeting is only exacerbating the green reflection on their face and clothes.

Technical question: is there any particular (technical) reason why bright green is the preferred colour for CSO/VR sets? Red would've been a good alternative, given the amount of red also present in the real and virtual sets. A slight red reflection on the main set from the VR section of the studio wouldn't look quite as out of place.


Red is too close to skin tones. I think there is also a technicial reason for using green in the digital domain.


Also, the CSO keying is constantly 'in circuit' I believe... So any camera is free to swing around to the VR area of the studio at anytime... the set needs to be a different colour to the CSO cyclorama.
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Rkolsen1,183 posts since 20 Jan 2014
BBC World

They used a curved VR set last night (with Julian O'Neill reporting) to illustrate some of the main headlines from the budget. I suspect we'll be seeing much more of this particular VR set.

Not quite sure why they've opted for the rectangular arrangement for the sports segment. And unfortunately the presenter's close proximity to the physical green sheeting is only exacerbating the green reflection on their face and clothes.

Technical question: is there any particular (technical) reason why bright green is the preferred colour for CSO/VR sets? Red would've been a good alternative, given the amount of red also present in the real and virtual sets. A slight red reflection on the main set from the VR section of the studio wouldn't look quite as out of place.


Red is too close to skin tones. I think there is also a technicial reason for using green in the digital domain.


Also, the CSO keying is constantly 'in circuit' I believe... So any camera is free to swing around to the VR area of the studio at anytime... the set needs to be a different colour to the CSO cyclorama.
I assume they're using VizRT engines for the VR set? That must cost a pretty penny with tracking devices and dedicated engines for each camera plus the engines for graphics.
noggin12,115 posts since 26 Jun 2001
Exactly, there are two other reasons why cameras "see" green better than any other colour, the first is the sensor itself single sensor cameras / CMOS chips have tightly packed Red, Green and Blue photo diodes, the alignment of which gives a slightly higher number of Green senors to any other, see image:

*



Valid for location recorded content - but single-sensor cameras are kind of unheard of in studios (other than very cheapskate operations using BlackMagic cameras). The Sony F55 briefly had a life as a location 4K camera - but OB providers were all waiting for 2/3" 3 sensor cameras to arrive (and they did in the shape of the HDC4300) as large single-sensor cameras with shallow DoF are not a good mix for fast moving sports coverage.

Quote:

The second sensor type, CCD uses 3 separate sensors for Red, Green and Blue, and uses a prism to separate the colours. This time greens place right in the middle of the visible light spectrum makes it the best colour to be received in this setup and thus the best to key with.

Further reading: http://www.techradar.com/news/video/the-science-behind-green-screen-1301075


You've missed the real point.

Most studio operations use 8 or 10 bit digital YCbCr 4:2:2 subsampled chroma for studio signal routing (not equal bandwith RGB - even though RGB cameras with 3 CCDs can normally deliver a full RGB equal bandwith signal at the camera head - unless pixel-offsetting has been used).

In SD 601 Y=0.587G + 0.299R + 0.114B
In HD 709 Y= 0.715G + 0.212R + 0.072B

As you can see there is a lot more green information in the high-bandwidth luminance channel than there is blue (red isn't used because of lips). If you want a clean chroma-key you get a cleaner result from using green. If you look at the maths, you have between 59 and 72% of the green signal in the double-bandwidth luminance channel, whereas you only have 0.07 to 0.14% of the blue signal in that channel (In 8 bit that would be somewhere between 16 and 32 levels between 0% and 100% blue meaning any blue HF detail has a very low number of quantisation states (8 bits carrying a 7% max signal doesn't give you many levels to play with...) The bulk of the blue signal information is carried in the Cb signal which is half the horizontal bandwith of the luminance, Y, signal.

This is also why chroma-key from a 4:2:0 or 4:1:1 format is usually not recommended (i.e. the various DV flavours and the low-bitrate MPEG2 LongGOP stuff like XD Cam 4:2:2 33Mbs)

In the days of analogue studios, you could usually get a high quality RGB or YPbPr analogue component signal from the camera CCU to feed to the mixer (you didn't key off the composite source that was the fill) and this was able to deliver a high quality clip from blue or green. With digital studios you are often better off with green. Downside was, of course, you couldn't chroma-key from anything other than the live cameras (you couldn't get a good quality chroma key from a composite 1" or 2" VT recording of the source camera - so if you wanted to key in post-production you had to use a second VTR to record the key signal generated by a chroma-key box 'live')

Things changed when got Beta SP and CRV component sources arrived which could be connected to the chromakey inputs of vision mixers of course...
Last edited by noggin on 18 March 2016 5:39pm
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rob6,808 posts since 7 Apr 2001
Meridian (South) South Today
Does anyone have a video montage of the set in action? I searched YouTube and they had a complete newscast up but it was embargoed because there was a clip of Six Nations Rugby.


I've re-uploaded it, with the offending content removed.

Last edited by rob on 19 March 2016 7:44am
tvlive.org.uk - the home of election presentation
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Austin Tatious448 posts since 1 Jan 2016
HTV West Points West
Why do they use a DOG anyway? The other regions don't.


Perhaps because BBC NI is in the same 'main channels crowd' as the broadcasters south of the border, and of course all channels (BBC, UTV, RTE, TV3, TG4) are routinely viewed north and south.


Unless there is a permanent DOG (e.g. "BBC One NI" or similar) on screen during the 99.9% of the time that anything other than a Newsline bulletin is on air, then the "BBC Newsline" DOG surely hardly fits this suggested reasoning? Therefore, it still seems pretty pointless to me.

Did Newsline (or even its predecessor "Inside Ulster") ever have a DOG before the first generic look came along in autumn 1999?
I am the one viewer of ITV West News.
Markymark4,472 posts since 13 Dec 2004
Meridian (North) South Today
Why do they use a DOG anyway? The other regions don't.


Perhaps because BBC NI is in the same 'main channels crowd' as the broadcasters south of the border, and of course all channels (BBC, UTV, RTE, TV3, TG4) are routinely viewed north and south.


Unless there is a permanent DOG (e.g. "BBC One NI" or similar) on screen during the 99.9% of the time that anything other than a Newsline bulletin is on air, then the "BBC Newsline" DOG surely hardly fits this suggested reasoning?


Well it might, the Beeb might think it's important that people know they are watching their news, and not any other news programme at that time of day. (I never thought I'd see myself defending use of a bloody DOG !)
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