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Shooting green screen on DVC HD


Tjerker

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Can you tap the SDI out of the camera head before it gets compressed? That would work best, I think. You can pull a great key no problem for most video applications even on tape, but you'll want the cleanest signal possible if it's high-end compositing for a film-out.

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Can you tap the SDI out of the camera head before it gets compressed?  That would work best, I think.  You can pull a great key no problem for most video applications even on tape, but you'll want the cleanest signal possible if it's high-end compositing for a film-out.

 

It's for a film-out but we're on a tight budget. Considering data rates and storage issues, we're quite impressed by the Panasonic - Apple route. But we have a lot of greenscreen (50 min+) work...

 

What do you think?

 

regards,

 

T.

Edited by Tjerker
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It's for a film-out but we're on a tight budget. Considering data rates and storage issues, we're quite impressed by the Panasonic - Apple route. But we have a lot of greenscreen (50 min+) work...

 

What do you think?

 

regards,

 

T.

 

Nowadays with the right tools you can pull decent keys from compressed footage, but tweaking this takes alot of time and as i said, you wont get there with every standard tool.

So, if you speak of 50 min and for the big screen...I can't really recommend that solution.

Maybe do a test before.

check out

http://www.dvgarage.com

it's meant for dv but i'd test it with your DVC HD footage too.

 

-k

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I dont havs hand on knowlege of this, but I do have some book knowlege.

 

Of course it will "Work", the question is how well will it work? Not as good as shooting 35mm on the greenscreen, Then the viper is probably the next step down, then F950, F900 and then the Varicam.

 

The higher the resolution, the better the result.

 

If I where you, I'd spend a little more and get a Viper outfit with a Sony HDCAM SR SRW-1 Recorder.

 

Good thing about the SRW-1 is that you can record @ 880MBPS!!! Compare that to the Compression on the Varicam, which I'm having trouble finding the Compression rate, but It cant be more than the F900, which is 100MBPS.

 

Of course a lot of productions could not afford this setup. Figure a Varicam will run $900.00/day (Which includes Camera and recorder) to $3,200.00 or so for a Viper and HDCAM SRW-1.

 

Of course this is just camparing the Specs, and thats not a such a good idea in normal everyday comparison. But it's hard to argue with me on that fact that Viper with this setup would be better than the Varicam....

 

As I have said before, you get what you pay for!

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Hi,

 

> Compare that to the Compression on the Varicam, which I'm having

> trouble finding the Compression rate, but It cant be more than the

> F900

 

I'd be interested to hear why you think it can't be. If they ran the tape fast enough, it could be. Please, let us know why you empirically know this to be the case.

 

> which is 100MBPS.

 

No, HDCAM records between 112 and 140mbps, depending on the frame rate.

 

 

> But it's hard to argue with me on that fact that Viper with this setup

> would be better than the Varicam....

 

No, it isn't. Define "better". Viper requires more crew, comprises a vast equipment package and costs a fortune to postproduce - you haven't thought this through. Viper produces either HDCAM-SR recordings or DPX files, which are very expensive to handle. Varicam would not only cost less to shoot (and then not only because of equipment costs) but also to postproduce.

 

Phil

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First of all... With 50 minutes of footage... you have got to shoot a test. Listen to these words of wisdom please. You need to know what you are getting into. I have seen so many projects started like this and never get finished. Projects that had budgets that the camera cost was not even a consideration - yet they still could never finish. In fact I can think of no less than four shot productions (some with stars even) that were abandoned because they didn't realize how much work it would be to shoot on green screen. Sky Captain was not supposed to cost 210 million dollars (the whisper budget number) - it was supposed to be something like 60 maybe 30 - "Hey I did this in my garage!"

 

So - think before you jump.

 

Now... One thing I would encourage you to consider very seriously is do you really need to shoot it all on green screen - are there things you could shoot with a small set and then expand on it?

 

My crew does blue and/or green screen composites every day from HD footage. I'll tell you what happens - with today's technology a quick key is really easy to pull.... IN STILL. Once it starts moving that's where you start seeing all the issues. Then you have to make adjustments - then one part looks good one way, another part is different, so you start garbage matting out each part os the frame, pull separate keys for legs, arms, heads, etc.. On shows that have 100 million budgets even this is done.

 

Now, if you're not that concerned about quality - then it's not such a big deal.

 

Okay - I will admit there have been a couple shots that keyed perfectsly with no intervension... rare... and always closeups.

 

I saw the dvgarage tool and was curious to test it against what we use (keylight in shake and after effects). I didn't find, personally, while testing it on DV footage that it was any better for that than keylight. It defaults to a softer key. The problem with DV compression in particular is that it creates big blocks - that's how it compresses... it's just about exactly the opposite of what you would want for keying... because all your smooth lines start to alias into these compression blocks. Generally whenever anyone has pulled a key from it that worked, it was very systlized, soft edged. I've never seen a perfect crisp key from DV compression.

 

Try it for yourself.... because you WILL be doing a test... right? No, seriously - you need to do a few shots and see how long it takes you before you find yourself 2 years into a nightmarish post production process.

 

and.... have fun! :-)

Edited by Mark Douglas
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I'd be interested to hear why you think it can't be.

Well, yeah, but they could also run HDCAM SR tape faster then..... The point is they don't right now. I dont think they varicam can record @ 880MPBS can it? If it can, please filll me in.

 

No, HDCAM records between 112 and 140mbps, depending on the frame rate. Compare 140MBPS to 880MBPS then...

Well, its still AROUND 100MBPS..... Theres not a huge differnece in 112 and 100. Or even 140 and 100.

 

Define "better"

High Resolution, Lower Compression, 2.39:1 Aspect Ratio, Does not use a lot of video processing like Sony and Panasonic Does..... Must I go on?

 

Viper requires more crew

Really? How is that? It seems it would require less to me. I can see needed an operator, 1st Assistant, 2nd Assistant, HD Tech, Cable Person, Video Playback person, ect. No more than what woould be needed to operate any other HD camera.

 

It may take a few more people to operat the VTR since its not right on the camera. If I'm missing something please inform me!

 

P.S) In the first place, I said nothing about it would'nt take more crew or more money or more time. I simply said it would produce a better image (Meaning Lower Compression, 2.39:1, Unprocessed, ect)..... I dount its cheaper or easier, but you get what you pay for. And you get back out of the matterial how much effort you put into it.

 

I'm not having a fight here, Agree with me or not, It's my view on it.

Edited by Landon D. Parks
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Quoted from www.filmandvideomagazine.com:

 

"In the Viper FilmStream Camera, directors of photography have a product that can capture true film-like images in their purest electronic form, eliminating the filtering and processing typically required to boost the quality of those images for post production," said Marc Valentin, vice president of the Thomson Broadcast Solutions business. [an error occurred while processing this directive] Capturing Every Bit of Information

The Viper FilmStream Camera differs from other forms of electronic and digital image acquisition in that it captures every bit of information a scene has to offer in a non-destructive, transparent, and reproducible way -- with no traditional video processing. The camera's optical block contains three unique 9.2 megapixel CCDs for a total of 27.6 million pixels. This design lets it work in several progressive scan formats: 1080 lines at 24/25/30 frames per second as well as 720 lines at 50/60 frames per second. In addition, when set in the 720 lines mode at 60 frames per second, it offers slow-motion effects at many different playback speeds during post production.

 

Using the Viper FilmStream Camera, post-production tools actually know how many photons have reached every one of the camera's 27.6 million CCD pixels -- just like individual grains of film react to light. Post-production operators can then change the visual and emotional impression in a picture in any way, since no information has been lost through video pre-processing and filtering.

 

To achieve its true film-like output, the CCD signals of the Viper FilmStream Camera, from pure black to CCD saturation, are captured with 12-bit A/D converters and then converted to RGB data values using 10-bit logarithmic calculations. These calculations enable the camera?s output to look more like film than any other digital cinematography system available, while taking advantage of the full dynamic range every CCD (red, green, and blue) has to offer.

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I saw the dvgarage tool and was curious to test it against what we use (keylight in shake and after effects).  I didn't find, personally, while testing it on DV footage that it was any better for that than keylight.  It defaults to a softer key.  The problem with DV compression in particular is that it creates big blocks - that's how it compresses... it's just about exactly the opposite of what you would want for keying... because all your smooth lines start to alias into these compression blocks.  Generally whenever anyone has pulled a key from it that worked, it was very systlized, soft edged.  I've never seen a perfect crisp key from DV compression.

 

Try it for yourself.... because you WILL be doing a test... right?  No, seriously - you need to do a few shots and see how long it takes you before you find yourself 2 years into a nightmarish post production process.

 

and.... have fun!  :-)

 

It's a very low budget :-( So postproduction costs are a big issue. That's why we consider the VariCam in the first place. But setting up a test shoot if we know beforehand that it won't work - hence the question.

 

Is digibeta a consideration? Will it give a better picture keyed and blown up to 35 mm projection?

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How low is this budget? Because who is doing the backgrounds and the composites? I mean off the top of my head it sounds like at least 200,000 of work there - maybe 100,000 if your a master deal maker.

 

50 minutes - lets figure that's got to be at least 400 cuts with at least 100 different backgrounds. Let's say each background takes one artist about 3 days to create. Let's say each composite for each shot takes a day with some being a lot faster and some being a lot longer. Yeah - if everything was shot perfectly and there were no problems, you could probably pop off a ton of them - or you accept a little quality loss... but I have a feeling you're not going to have the perfect stage and your not going to have all the time you want to shoot.. so back to what I just said.

 

So it looks like you have about 2 years worth of single artist man power ahead of you. Maybe you have a bunch of friends who will help. Unless they are seriously indebted to you and you really can trust them... don't - maybe a few will deliver, but the rest won't.

 

I'm really, sincerely, not trying to bum you out. I'm trying to protect you. I've been doing this crazy "do it yourself" / "homestyle" / "garage" special effects and bg stuff for over a decade and I just want you to know what you're looking at. Sounds like you don't have a lot of cash - you sure as hell don't want to spend it all on something that is unfinishable - or if it does finish doesn't look great.

 

 

Anyway - so... that's why I'm saying... do a test... do a test on whatever you can get your hands on (even a dv camera) just to test the whole process.

 

As far as cameras go... The bigger the resolution, the less the compression, the greater lattitude of the colors - the better. And interlacing will not be your friend.

 

As for resolution vs. compression... totally depends on the grades and I'm afraid that's knowledge I don't have - other people here obviously do.

 

....and........... have fun! :-)

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Hi,

 

> Well, yeah, but they could also run HDCAM SR tape faster then..... The point is

> they don't right now.

 

No, the point is that you made statement that wasn't necessarily true based on nothing but some random idea you had in your head, which you shouldn't do.

 

> Well, its still AROUND 100MBPS..... Theres not a huge differnece in 112 and 100. Or

> even 140 and 100.

 

Yes, there is! 140 is almost half as much again!

 

> High Resolution, Lower Compression, 2.39:1 Aspect Ratio, Does not use a lot of

> video processing like Sony and Panasonic Does..... Must I go on?

 

Yes. You must also considert the practicalities of shooting with the device, especially if you're going to make a case based on the cost of doing it, which you did.

 

> Really? How is that? It seems it would require less to me.

 

Yes, again, it seems that way to you because you haven't got sufficient background on the subject. You can shoot Varicam with an ENG crew if you like. There is no opportunity to do that with Viper.

 

Phil

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Is digibeta a consideration? Will it give a better picture keyed and blown up to 35 mm projection?

Betacam is SD, Varicam is HD. Even though Varicam is not top notch HD, it is still HD. And the difference between SD and HD is like the difference in Earth and the moon.

 

Betacam will work, just as Varicam will work and even Hi8 Video will work. But it comes down to a matter of how well it works vs. how well you need it to work.

 

How are you releasing this?

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How low is this budget?  Because who is doing the backgrounds and the composites?  I mean off the top of my head it sounds like at least 200,000 of work there - maybe 100,000 if your a master deal maker.

 

50 minutes - lets figure that's got to be at least 400 cuts with at least 100 different backgrounds.  Let's say each background takes one artist about 3 days to create.  Let's say each composite for each shot takes a day with some being a lot faster and some being a lot longer.  Yeah - if everything was shot perfectly and there were no problems, you could probably pop off a ton of them - or you accept a little quality loss... but I have a feeling you're not going to have the perfect stage and your not going to have all the time you want to shoot.. so back to what I just said.

 

So it looks like you have about 2 years worth of single artist man power ahead of you.  Maybe you have a bunch of friends who will help.  Unless they are seriously indebted to you and you really can trust them... don't - maybe a few will deliver, but the rest won't.

 

I'm really, sincerely, not trying to bum you out.  I'm trying to protect you.  I've been doing this crazy "do it yourself" / "homestyle" / "garage" special effects and bg stuff for over a decade and I just want you to know what you're looking at.  Sounds like you don't have a lot of cash - you sure as hell don't want to spend it all on something that is unfinishable - or if it does finish doesn't look great.

Anyway - so... that's why I'm saying... do a test... do a test on whatever you can get your hands on (even a dv camera) just to test the whole process.

 

As far as cameras go... The bigger the resolution, the less the compression, the greater lattitude of the colors - the better.  And interlacing will not be your friend.

 

As for resolution vs. compression... totally depends on the grades and I'm afraid that's knowledge I don't have - other people here obviously do.

 

....and...........    have fun!  :-)

 

The movie is a cooperation of a lot op people, including artists with a lot of experience. SD and chromakey / greenscreen is not new for us - but only on digitbeta material. HD / film is completely new for all of us. We will work with partly built sets. We will have access to a proper stage. We won't have a lot of time, though, and no money.

 

We're querious how digibeta footage relates to DVC HD stuff. Is it better? Equal? Worse?

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We're querious how digibeta footage relates to DVC HD stuff. Is it better? Equal? Worse

Again, DVC HD is HD, Digibeta is SD. Digibeta is Interlaced, Varicam is Progressive scan, Digibeta has like 500,000 pixels, Varicam has 1.1 Million. Varicam is not as compressed as digibeta....

 

Of course There will be a difference in the quality, and most people will be able to see it. Recently I was shown a test of a Varicam vs. HDW-900.... You would be surprised how much difference a little lower compression and twice the amount of pixels make.

 

If you have plans to shoot with a varicam, at least use a HDW-F900. You can get them now for $1,200.00/day where as a Varicam will run you at least $900 if not $1,000.00.

 

You really can tell the differnce between 1.1 Million and 2.2 Million pixels, trust me. Even more if it's on greenscreen, where you need every last pixels you can get. It's worth another $200/day.

 

But back to your question; No, Digibeta will not be as good as DVC PRO HD. As fare as Image quality anyway. It may be cheaper to shoot, but again we com back to my original statement: "You get what you pay for!"

 

Just my opinion on the matter.

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Right - from a post production perspective (we spend all day doing green screens!!)....

 

Its true that a varicam has a lower resolution. It's frame size is 720 "lines" high. If your film is going to be distributed as a 1:1.85 picture, then your film out image will most likely be 988 lines high. Remember that the output of the varicam image is actually "upres'd" to 1080 lines high on output though. An F900 (or whatever) records 1080 lines in the first place.

 

HOWEVER, the big issue here is colour resolution. Varicam is 4:2:2 and HD-CAM is 4:1:1, meaning its colour information is much more compressed. We'll assume that for budget reasons a 4:4:4 solution (F950 and disks) is out of the question, although this is the ideal for green screens. When dealing with green screen keys, colour seperation is the big issue. I would very strongly suggest that you will get better keying results with a 4:2:2 varicam than a 4:1:1 HD-CAM, despite the increased pixel resolution.

 

About that apple solution. Let me just say that green screen work (post) is very difficult and takes a great deal of skill. What tool you have in front of you is largely irrelevant as long as it actually has the toolset you need. No matter what the manufacturers say, green screen comps are never automatic! Also, there are a lot of processes used to make green screens look good (keying, matt correction, edge correction, colour correction etc etc) and if you use a single computer, be ready for a very, very long post session :-)

 

Definitely do some tests so you know what you are letting yourself into. By all means contact mean through our web site if you need more info.

 

Good Luck!

 

David Cox

Managing Director

Baraka Post Production Ltd

www.baraka.co.uk

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Oh yeah, I forgot to say...

 

Do you know the biggest single problem we get with green screens? Resolution? Lighting? Compression? NO! Around 1/3rd of the green screen shoots we get where we have not been involved in the shoot, have the green screen TOO SMALL so we end up hand matting anyway!

 

Top Tip: Buy green, lots and lots of green!

 

David Cox

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About that apple solution. Let me just say that green screen work (post) is very difficult and takes a great deal of skill. What tool you have in front of you is largely irrelevant as long as it actually has the toolset you need. No matter what the manufacturers say, green screen comps are never automatic! Also, there are a lot of processes used to make green screens look good (keying, matt correction, edge correction, colour correction etc etc) and if you use a single computer, be ready for a very, very long post session :-)

 

Definitely do some tests so you know what you are letting yourself into. By all means contact mean through our web site if you need more info.

 

Good Luck!

 

David Cox

Managing Director

Baraka Post Production Ltd

www.baraka.co.uk

 

The 'Apple solution' I'm considering is: shooting varicam, edit in Final Cut, distribute footage of FX scenes to a bunch of artists via harddisks, get them back and piece everything together again. The 'artists' involved are 3d / matte painters / compositors. Makes any sense?

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Hi,

 

> Varicam is 4:2:2 and HD-CAM is 4:1:1, meaning its colour information is much more compressed

 

First off HDCAM is not 4:1:1, it's 3:1:1, which is slightly better, but that's not what's interesting here.

 

I've been thinking about this, and by the time you get back to a 1920x1080 image, the situation changes. Think about it:

 

F900 records a 1440x1080 image and subsamples 3:1:1 for 480x1080 UV planes.

 

Varicam records a 960x720 image and subsamples 4:2:2 for 480x720 UV planes.

 

F900 records more detail in colour than Varicam, popular prejudice be damned!

 

Phil

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The 'Apple solution' I'm considering is: shooting varicam, edit in Final Cut, distribute footage of FX scenes to a bunch of artists via harddisks, get them back and piece everything together again. The 'artists' involved are 3d / matte painters / compositors. Makes any sense?

Yes, it makes since. Although thats not the only way to do it, generally it can be done that way.

 

I would personally avoid all the hard disk's and just network your FCP computer with the VFX computers, this way you can send the data to any computer on the network at Eithernet Speed (Forget what maximum speed is now).

 

It would be cheaper to pack all the VFX computers and the FCP computer into an area to allow them to be networked than to spend thousands on hard drives (Yes, it probably will cost that much!).

 

as to the matter of sub sampling and all that jazz..... If you can get it uncompressed, the better. Because while your shooting the greenscreen you need the maximum of quality you can get, because your not just dealing with a live color image, your dealing with an image that the computer has to erase greenscreen around the actor or object in the scene.

Edited by Landon D. Parks
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I would just like to know if anyone believes that good keys can be taking from vericam footage? Has anyone seen any good keys from the f900 or 950? I am stuck right now between using the sony and the vericam. I have some green screen footage to shoot as well, but I also need to record in slow motion. Obviously the vericam is better for higher speed shooting, but the sony has better resolution. Does anyone believe it can be done, are there any tricks to help mask "almost perfect keys" anyone would like to share?

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The 'Apple solution' I'm considering is: shooting varicam, edit in Final Cut, distribute footage of FX scenes to a bunch of artists via harddisks, get them back and piece everything together again. The 'artists' involved are 3d / matte painters / compositors. Makes any sense?

 

...yes this does make sense. I assmume the hard drive based distribution is because your artists are in different locations. Here in Soho London, hard disks are cheaper than office space (to house everyone on a network) so there is some logic there!

 

The only word of caution I would offer is to make sure that individual operators work entirely on a single sequence, rather than have a sequence made up of shots from different operators. The reason is that green screening normally requires a lot of subjective and creative work. For example, colour correction of foreground / background, softness of edges, influence of the new foreground on its background such as shadows, reflections, colour additions etc. If you have two operators in two locations working on the same sequence, they may well have different interpretations of these values. Both of their shots may look fine, but cut together back-to-back they might show their differences.

 

Good luck

 

David Cox

Managing Director

Baraka Post Production Ltd. London

www.baraka.co.uk

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F900 records a 1440x1080 image and subsamples 3:1:1 for 480x1080 UV planes.

 

Varicam records a 960x720 image and subsamples 4:2:2 for 480x720 UV planes.

 

Phil - interesting maths. It would be interesting to test two identical set ups back to back, wouldn't it!

 

Actually though, the biggest culprit for bad green screen shots (as in ones that take forever to get right) is simple bad shooting technique. I think beyond that, the camera and compression choice have an affect, but not as dramatic as a badly lit screen (or screen too small!)

 

In general, here are your watch points for green screen work...

 

Make sure the screen is big enough and covers the whole foreground moving action. Sounds obvious, but about a third of shots given to us have a screen too small and then your just left with drawing round things, frame by frame.

 

Think about what the computer "sees" and think about colour seperation. The computer is looking only at colours, not at shapes. At the start, it assumes perfect flat green, but every fold and shadow on the green screen is technically a different colour, so we widen the "search" for green to encompass these colours also. However, where there is motion blur, for example on the edge of a moving hand, this too is actually just a range of colours from green to skin tone. So if we widen our search for green to get all those folds and shadows from the green background, we also include those blurred edged that actually we would want to exclude. So the very best green screen would be as flatly lit, i.e. a uniform green, accross its full width. Remember also that film grain or camera gain noise will also "unflatten" the green.

 

Obviously green foreground items need to be avoided (if you want to keep them in your shot) but also pay attention to colours that include green. For example, your eye sees turquoise, the computer sees a mix of green and blue.

 

Within reason, don't worry too much about green spill - i.e. light that has bounced off the green screen and is now casting a green hue on the foreground object. Modern systems handle this very well. Just watch out for anything that is really reflecting the green - shiny floors and tabletops etc

 

As for the brightness of the green screen, here is the dilemma. The darker the green, the closer it is to black where there is no difference between the colour channels. The lighter it is, the closer it is to white, where there is no difference between the colour channels. So the ideal is a mid brightness, highly saturated green - although if your foreground is light, darken your green screen a bit and vice-versa. Again, think about the difference between your foregound and background. That's what the computer is working on.

 

If shooting on film, when it comes to telecine, make sure the operator doesn't do too much processing to the green pass. Sometimes, they try to improve the green by keying green into the screen. This just gives your compositor a keyed green screen to key again, and this can adversely affect the edges.

 

Theres a million other small things, lighting direction etc, but I'm going on a bit! But to get back to the thread, I think my point is that technically the ideal is an uncompressed 4:4:4: camera / recorder, but given a restricted budget you are more likely to benefit green screen shoots by getting an extra light for your screen the qubbling between 720P 4:2:2 varicam or 1080P 4:1:1 sony.

 

David Cox

Managing Director

Baraka Post Production Ltd

www.baraka.co.uk

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  Theres a million other small things, lighting direction etc, but I'm going on a bit! But to get back to the thread, I think my point is that technically the ideal is an uncompressed 4:4:4: camera / recorder, but given a restricted budget you are more likely to benefit green screen shoots by getting an extra light for your screen the qubbling between 720P 4:2:2 varicam or 1080P 4:1:1 sony.

 

David Cox

Managing Director

Baraka Post Production Ltd

www.baraka.co.uk

 

That helps! Thanks!

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Hi Tjerker

very happy to have found your thread.

i was given a job shooting an intro for a TV show, using a Varicam and a bluescreen.

(The production decided on the camera)

I have never used the camera before, and only done bluescreen twice before.

I was about to post when I read this.

So to everyone who have replied (specially David Cox), thanks alot.

Good luck Tjerker

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