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Uncompressed Green Screen Image


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#1 Gavin Greenwalt

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Posted 10 October 2006 - 04:37 AM

RED.com posted an uncompressed Green Screen image in 48bit linear RGB.

My personal impressions are very very positive. I won't go in depth here, I already posted most of my specifc comlaints on DVXuser but there were some artifacts from either the sensor or the demosaic processing (or the lack of processing) which arose. None of them should be visible under normal circumstances and really are only trouble when you start keying. Don't get me wrong though when I say "trouble" I mean... it didn't key itself. Even this rough, poorly lit footage is some of the nicesest cleanest footage I've had the pleasure to work with. I have very very high hopes for this camera at least from a post-production stand point.

And of course there is a mini contest to see what people can do with it.

This shouldn't be taken as an example of what's possible since I was just messing around but it can produce very good mattes:
http://i111.photobuc...posite_test.jpg
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#2 Stephen Williams

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Posted 10 October 2006 - 01:04 PM

RED.com posted an uncompressed Green Screen image in 48bit linear RGB.

My personal impressions are very very positive. I won't go in depth here, I already posted most of my specifc comlaints on DVXuser but there were some artifacts from either the sensor or the demosaic processing (or the lack of processing) which arose. None of them should be visible under normal circumstances and really are only trouble when you start keying. Don't get me wrong though when I say "trouble" I mean... it didn't key itself. Even this rough, poorly lit footage is some of the nicesest cleanest footage I've had the pleasure to work with. I have very very high hopes for this camera at least from a post-production stand point.

And of course there is a mini contest to see what people can do with it.

This shouldn't be taken as an example of what's possible since I was just messing around but it can produce very good mattes:
http://i111.photobuc...posite_test.jpg

¨
Hi,

With all due respect IMHO that is a fairly poor key. It looks cut out and the edges have been softened.

Stephen
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#3 Gavin Greenwalt

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Posted 10 October 2006 - 02:18 PM

¨
Hi,

With all due respect IMHO that is a fairly poor key. It looks cut out and the edges have been softened.

Stephen


Your humble opinion is correct. That's a very fast single key without garbage masking any of the difficult areas for isolated controls. i.e the hair and the chain saw are being keyed on the same key without a patch on an unevenly lit green screen. Also the foreground was looking disproportionally crisp to the lower res photo I just had lying around so I blurred the foreground 3 pixels. That matte doesn't even have the levels on it adjusted.

If I really needed to create a quality matte I would have built the keyer in Shake, but I was just playing and trying to break the image in combustion, using the only photo I had that was large enough to cover the frame at least mildly well.

Which is why I wanted to put up a disclaimer saying this wasn't an example of the quality of the green footage. (Or me for that matter while I'm being an apologist.) ;) Go to RED.com and look at the footage. I'm interested to hear if other people are encountering the same artifacts I was, or if I was just imagining things. I don't want to be specific because I don't want to plant ideas in other people's heads if I'm just crazy.

- Gavin

Edited by Gavin Greenwalt, 10 October 2006 - 02:21 PM.

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#4 Stephen Williams

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Posted 10 October 2006 - 02:32 PM

Your humble opinion is correct. That's a very fast single key without garbage masking any of the difficult areas for isolated controls. i.e the hair and the chain saw are being keyed on the same key without a patch on an unevenly lit green screen. Also the foreground was looking disproportionally crisp to the lower res photo I just had lying around so I blurred the foreground 3 pixels. That matte doesn't even have the levels on it adjusted.

If I really needed to create a quality matte I would have built the keyer in Shake, but I was just playing and trying to break the image in combustion, using the only photo I had that was large enough to cover the frame at least mildly well.

Which is why I wanted to put up a disclaimer saying this wasn't an example of the quality of the green footage. (Or me for that matter while I'm being an apologist.) ;) Go to RED.com and look at the footage. I'm interested to hear if other people are encountering the same artifacts I was, or if I was just imagining things. I don't want to be specific because I don't want to plant ideas in other people's heads if I'm just crazy.

- Gavin


Hi Gavin,

Trying to download but it's saying 3 hours left!
I will have a look later if I can!
From looking at other examples I get the feeling that the camera was not perfectly in focus.

Best wishes,

Stephen
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#5 Stephen Williams

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Posted 10 October 2006 - 03:59 PM

Hi Gavin,

Well I have downloaded from the Red site. Not sure where the focus is supposed to be, or if the FFD is correctly set on the camera! There are some bright green (edging) around his arm.

I don't see how anyone is expected to do a high end composite from such a shot!

Can somebody with more Red experience explain what the point is of showing this image?

FWIW I do think the bubble footage is very good.

Stephen
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#6 Gavin Greenwalt

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Posted 10 October 2006 - 05:36 PM

Hi Gavin,

Well I have downloaded from the Red site. Not sure where the focus is supposed to be, or if the FFD is correctly set on the camera! There are some bright green (edging) around his arm.

I don't see how anyone is expected to do a high end composite from such a shot!

Can somebody with more Red experience explain what the point is of showing this image?

FWIW I do think the bubble footage is very good.

Stephen


"Not perfectly" is an understatement. Part of the reason why I didn't bother trying to get a perfect key. Although I still haven't decided if it's out of focus or just blurry because he's holding a vibrating chain saw.

I noticed the green glow too. That was one artifact, however it appears to me like it's more global than just on the edges. Any part that is motion blurred seems to be over saturated. Also another thing that I noticed that is contributing to that edge is there seems to be a luminance fade or glow, I'm not sure which around all high contrast shifts. (Think back like the 1950s TV cameras with the black glow). This is something I want to confirm before saying it's a problem, but I have a suspicion this is happening.

I'm assuming many of these are a result of RAW uncorrected sensor artifacts since it's a whole swarm of problems I've never seen before on 4:4:4 footage. Normally it's the same problems to varrying degrees. We'll have to wait and see.

- Gavin

Edited by Gavin Greenwalt, 10 October 2006 - 05:40 PM.

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#7 Jaan Shenberger

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Posted 10 October 2006 - 07:37 PM

Hi Gavin,

Well I have downloaded from the Red site. Not sure where the focus is supposed to be, or if the FFD is correctly set on the camera! There are some bright green (edging) around his arm.

I don't see how anyone is expected to do a high end composite from such a shot!

Can somebody with more Red experience explain what the point is of showing this image?

FWIW I do think the bubble footage is very good.

Stephen


a good compositor could pull a totally invisible key & composite from that while eating a donut with one hand and reading msnbc.com on the other monitor.

no insult to gavin, just felt like stephen's remark is totally off-target. also, the green edge around his arm is a natural effect from the reduction in luminance from the motion blur (which brings the overexposed greenscreen down in luminance and therefore seeming to be more saturated). the shot does look pretty soft though.
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#8 Jaan Shenberger

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Posted 10 October 2006 - 07:51 PM

there does seem to be something weird going on with the red channel along any high luma contrast edges. i assume this is due to the RAW/bayer/etc conversion.

Edited by Jaan Shenberger, 10 October 2006 - 07:52 PM.

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#9 Stephen Williams

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Posted 11 October 2006 - 02:07 AM

a good compositor could pull a totally invisible key & composite from that while eating a donut with one hand and reading msnbc.com on the other monitor.

no insult to gavin, just felt like stephen's remark is totally off-target. also, the green edge around his arm is a natural effect from the reduction in luminance from the motion blur (which brings the overexposed greenscreen down in luminance and therefore seeming to be more saturated). the shot does look pretty soft though


.


Hi,

Please send me a link to a composite with this footage that you think is 'good'. Then we can talk further.

Very few composites are ever 'totally invisible' IMHO.

I have recently shot some film that was scanned at 4k, I did not see this 'natural effect from the reduction in luminance from the motion blur'


Stephen
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#10 Gavin Greenwalt

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Posted 11 October 2006 - 04:34 AM

Hi,

Please send me a link to a composite with this footage that you think is 'good'. Then we can talk further.

Very few composites are ever 'totally invisible' IMHO.

I have recently shot some film that was scanned at 4k, I did not see this 'natural effect from the reduction in luminance from the motion blur'
Stephen


I'm not sure which part we're all looking at but Jaan is absolutely correct about the green fringe, that's normal to any composite. It's not only perceptive it's actually mathematically more saturated by reducing the exposure. You just probably normally don't see it because most green screens aren't as over lit as this.... cyan screen is.

I had some free time today to go back and actually visually inspect some of the artifacts that I'd subjectively observed when first looking at it last night.

The over saturation in the motion blurred areas I think is the result of vertical banding.

There is definitely something wrong with the prototype de-mosaicing process on the green. If you look at the green channel on the pumpkin, you can see a checker board pattern in the pixels. Across the whole image the green pixels on even numbered (starting with 0) rows can have problems and I think also even on the columns. Once you start keying I've found similar checker patterns out in the green screen as well.

Also I don't know much about Bayer patters but... is the blue channel only being half sampled? It looks like it's significantly under sampled in some spots. And it has a strange aliasing pattern on the pumpkin.

It appears my concerns about high contrast fringing were all in my head. I couldn't find any data to actually back that up on the image.

I suppose this is what we get when we ask to see behind the curtain. I'm sure Graeme right now is somewhere shaking his head and muttering "Shut up. we know, we know... we'll get to it."

Shadows seem to be the Mysterium's weakness right now. Can the vertical smearing be minimed through internal processing?

Edited by Gavin Greenwalt, 11 October 2006 - 04:35 AM.

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#11 Stephen Williams

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Posted 11 October 2006 - 05:48 AM

You just probably normally don't see it because most green screens aren't as over lit as this.... cyan screen is.

I suppose this is what we get when we ask to see behind the curtain. I'm sure Graeme right now is somewhere shaking his head and muttering "Shut up. we know, we know... we'll get to it."


Hi,

I assume this was not one of David Stump's tests!

Why on earth was such a shot released?

I did offer to shoot some test for Jim J, he personally refused my offer (on this forum)

Stephen
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#12 Jaan Shenberger

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Posted 11 October 2006 - 06:07 AM

I have recently shot some film that was scanned at 4k, I did not see this 'natural effect from the reduction in luminance from the motion blur'


that's because i'm sure you exposed your greenscreen properly.

Please send me a link to a composite with this footage that you think is 'good'. Then we can talk further.


if you wanna pay my dayrate, then just let me know.
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#13 Stephen Williams

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Posted 11 October 2006 - 06:16 AM

that's because i'm sure you exposed your greenscreen properly.
if you wanna pay my dayrate, then just let me know.


Jaan,

IMHO that shot is NG and is not worth using.

You said "a good compositor could pull a totally invisible key & composite from that while eating a donut with one hand and reading msnbc.com on the other monitor." I hardly think I need to pay your day rate, I will buy you a donut! :D

Stephen
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#14 Gavin Greenwalt

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Posted 11 October 2006 - 12:04 PM

Jaan,

IMHO that shot is NG and is not worth using.

You said "a good compositor could pull a totally invisible key & composite from that while eating a donut with one hand and reading msnbc.com on the other monitor." I hardly think I need to pay your day rate, I will buy you a donut! :D

Stephen


You also have to define what a totally invisible composite would be. In this case the matte would be fuzzy and out of focus. ;)

He released this in part because myself and a large number of other people asked him to. I'm relatively certain this was for internal testing. Jim posted a composite they did in house. The in house composite didn't get a very good response so he released it to the masses to let them take a shot at the same frame, as soon as the DVXuser competition ended Jim said something to the effect of "Ok now I can take it down."

My guess is they aren't letting people shoot anything of quality because they don't want any of their footage to be "official" yet. It's an interesting mindset difference I'm noticing. Coming from a 3D and FX background I'm used to working with Alpha or Beta software, sometimes even in production. Film people aren't quite so anxious to play with unfinished products. I guess you're able to take more chances when you're in the safe controlled environment of a green screen stage than on the side of a mountain with a crew waiting to roll.
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#15 Max Jacoby

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Posted 11 October 2006 - 05:34 PM

My guess is they aren't letting people shoot anything of quality because they don't want any of their footage to be "official" yet.

Pardon me?

I do fail to see the logic in your argument. What you're essentially saying is is that they are releasing 'inferior' footage of their camera. Now what on earth would be the point of that?
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#16 Gavin Greenwalt

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Posted 11 October 2006 - 08:45 PM

Pardon me?

I do fail to see the logic in your argument. What you're essentially saying is is that they are releasing 'inferior' footage of their camera. Now what on earth would be the point of that?


Ever hear of the old argument "you can't fail if you don't try." ;) It's not the most rational of arguments, but it seems to be the one they're following. As soon as you get some real footage out there, there will be no excuse. And admit it they're kind of right, wouldn't you evaluate footage shot by David Mullens more seriously?

They're walking a fine line. If they let professionals evaluate it before they've worked out all the kinks it'll probably get a bad rap. If they don't release any footage the professional community will accuse them of hyping vaporware. The best option seems to be the one they're following "Here's some footage we shot really quick in our garage one sunday. See it exists."

The green screen footage doesn't count in my argument since it was more leaked than released. It still doesn't explain though why nobody there knew how to properly light a green screen, unless they were purposely sabotaging the test. Let the conspiracy fly.
- Gavin

Edited by Gavin Greenwalt, 11 October 2006 - 08:46 PM.

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#17 Stephen Williams

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Posted 12 October 2006 - 01:51 AM

They're walking a fine line. If they let professionals evaluate it


Hi Gavin,

Somebody on CML once said " If you know how to light it does not matter what you shoot on" & "If you don't know how to light it does not matter what you shoot on" The green screen shot is a good example of this IMHO.

How can Red possibly evaluate their own work? I think somebody with more experiance of shooting green screens need to help them!

Stephen
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#18 Gavin Greenwalt

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Posted 12 October 2006 - 01:35 PM

Hi Gavin,

Somebody on CML once said " If you know how to light it does not matter what you shoot on" & "If you don't know how to light it does not matter what you shoot on" The green screen shot is a good example of this IMHO.

How can Red possibly evaluate their own work? I think somebody with more experiance of shooting green screens need to help them!

Stephen


If they shot that green screen footage for the purpose of evaluating the capabilities, agreed, they need some serious help. I'm hoping they were just having fun on a weekend. Then again... when I have fun on a weekend I usually break out 8k in soft boxes and spend several hours lighting a green stage. When the HVX first came out I borrowed one for an evening and shot some '4k' footage' by turning it on its side. I will say though. I would rather work with the RED's cyan out of focus screen even than the HVX.

One huge problem with that footage as a green scren test is the sharpness of the blue channel. Since the blue channel seems to be sampled at a lower rate (and was full of garbage) the 'green' screen data was likewise corrupted and infiltrated by its nefarious blue half. However it mostly looked like de-mosaic artifacts.

And this is a point where I would take exception to Jan's statement. It should have read: A good compositor can pull a good key off of *just about anything*.

- Gavin
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#19 Gary McClurg

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Posted 12 October 2006 - 01:37 PM

And this is a point where I would take exception to Jan's statement. It should have read: A good compositor can pull a good key off of *just about anything*. - Gavin


Also had it just costs more.... :D
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