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Old February 20th, 2007, 01:50 AM   #1
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hvx green screen question,

i'm taking my new hvx into the studeo thursday (hoping my p2 card arrives by then) and I need some advice, I've used another hvx in the greenscreen studeo several times and I keep getting the same results, the green channel looks perfect, the blue channel looks bad, and bother the red and blue channel has a white and black line around the subject, which comes out in the color channel when I pull the keys, and it screws up my alfa big time, I'm being forced to rebuild the edge of the subject which really stops being keying and starts being compositing tricks,

those I'm taking my hvx in and am going to test her for all shes worth,

the first set of settings I'm going to try are these

DETAIL LEVEL -3
CHROMA LEVEL +2
MASTER PED -2
GAMMA CINELIKE D
MATRIX NORM

but I'm wondering if anyone else has had this problem and how you fixed it if you did?

thank you
Jason Miller

I'm uploading a file to youtube that will give you an idea of the studeo, and the camera, its a shot with the hvx.

http://www.youtube.com/watch?v=ZlP8R1P0_LE

should be the link when the youtube people get off there butts and allow it to show. its been 30 minutes since I've uploaded it.

I will be thankfull for any tips on this camera.
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Old February 20th, 2007, 11:30 AM   #2
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Could you post some frame grabs?
It's hard to see what you're talking about from that video.
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Old February 20th, 2007, 01:30 PM   #3
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stills in each channel - alpha

red channel rrra
http://www.wafflefilms.com/redchannel.jpg

blue channel bbba
http://www.wafflefilms.com/bluechannel.jpg

green channel ggga
http://www.wafflefilms.com/greenchannel.jpg


color channel, rgba
http://www.wafflefilms.com/colorchannel.jpg


any advice anyone can give will be great, we were getting nicer keys with the beta. and I know this camera should get great keys, its 4:2:2 thats what most clipped film footage tends to end up as for keying.

Jason Miller

post script, this was shot before I knew about the detail settings that Barry Green recomends, I'm back in the studio thursday night, and I'm going to try them, but I'm hoping there may be other fixes as well, as I dont want to lose subject detail as well.

Last edited by Jason Miller; February 20th, 2007 at 02:50 PM.
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Old February 20th, 2007, 01:57 PM   #4
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Hate to burst your bubble, but your green channel doesn't look perfect. It has the same halo, aura, whatever you want to call it around the subject. The G channel contains most of the luma info so you don't see the halo in the same way, but it's there and it's the first thing I saw when I opened the G channel pic and the first thing I saw when I opened the full RGB pic - focus blur aura. It's hard to tell 100% from the compressed JPGs, but I see three problems:

1 > screen lighting. There's too much tone variation on the screen, the lighting needs to be more intense and more even. More lights - even light the screen with green lights / use green gels.

2 > Proximity. I think your subject is too close to the screen.

3 > Focus. It's out of focus... You're getting a soft aura on your subject and I'm wondering if you're using the camera in AF mode? Perhaps the lighting/color variation of the greenscreen is pulling your focus point away from the subject? Use a full-res external monitor to focus the shot... The on-board LCD is worthless and using typical HD-TV style LCD displays is often a bad idea due to their excessive image processing.
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Old February 20th, 2007, 02:48 PM   #5
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screen lighting can't be helped, its lite with keyno flos, and the powers that be think its perfect. several grand per light it would have to be (i say with much sacasim).

but the back ground being uneven can cause multi keys but it can't cause halo around the forground object,

distance, he was about 15 feet from the wall, we coudnt get further.


I try to never use AF unless I'm dealing with a dolly crane and am the onlyone on camera, but in this shot it was manual. I dont have access to a full res hd monitor, we have a really nice ntsc production monitor, but its pointless to use for color channels.

I'm not the only one running into this problem, everyone how uses the studios hvx has the same halo, I'm just really the only one trying to fix it.





Quote:
Originally Posted by Jeff Kilgroe
Hate to burst your bubble, but your green channel doesn't look perfect. It has the same halo, aura, whatever you want to call it around the subject. The G channel contains most of the luma info so you don't see the halo in the same way, but it's there and it's the first thing I saw when I opened the G channel pic and the first thing I saw when I opened the full RGB pic - focus blur aura. It's hard to tell 100% from the compressed JPGs, but I see three problems:

1 > screen lighting. There's too much tone variation on the screen, the lighting needs to be more intense and more even. More lights - even light the screen with green lights / use green gels.

2 > Proximity. I think your subject is too close to the screen.

3 > Focus. It's out of focus... You're getting a soft aura on your subject and I'm wondering if you're using the camera in AF mode? Perhaps the lighting/color variation of the greenscreen is pulling your focus point away from the subject? Use a full-res external monitor to focus the shot... The on-board LCD is worthless and using typical HD-TV style LCD displays is often a bad idea due to their excessive image processing.
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Old February 20th, 2007, 03:00 PM   #6
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The subject is way out of focus, which is going to make keying absolutely ridiculous.

If you don't have a high-res monitor, then you should change your settings so that your focus reads in distance, then measure the distance directly w/ a tape measure. Use EVF and Focus Assist to get your focus razor sharp. I've been shooting wildlife in the field using the built-in LCD monitor, EVF and distance readout and my focus is spot-on 8/10 times, even without Focus Assist.

The lighting on the screen is an issue, too, but if you said the powers that be want it like that, well, such is the way it is. So long as they're paying, be prepared to fight the key.
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Old February 20th, 2007, 03:33 PM   #7
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Quote:
Originally Posted by Jason Miller
screen lighting can't be helped, its lite with keyno flos, and the powers that be think its perfect. several grand per light it would have to be (i say with much sacasim).
Well, that sucks..... I would suggest showing them a few frame grabs, even of a blank green screen, and show them the tone variation. No reason the lighting needs to cost that much, you can try to explain that to them too. But I know where you're coming from, sometimes it can't be helped. Some "studios" don't want to admit that their "greenscreen" isn't up to par and/or their lighting sucks. Especially when they've spent thousands on hardware that's being improperly used or is the improper tool for the job.

Check out my attatched pic... This is a section of a frame grabbed from an HVX shoot at 720p24. It was a quick and dirty setup -- the green screen is a wall painted with flat green paint and lit via halogen shop lights (contractors' lights you buy at Home Depot or similar). There couldn't have been more than $150 in costs painting and lighting the screen and we were still tweaking the lights when this frame was shot. There is some edge halo in mine too, but it's from the JPEG compression more than anything. I can probably post a key later... We're not ready to show this project yet. I blocked out her face because of this and to save her some dignity - she had an undwerwear malfunction. ;)

Quote:
but the back ground being uneven can cause multi keys but it can't cause halo around the forground object,
I would say that's generally correct, but I never rule anything out. Uneven screen lighting can do lots of weird things, especially when dealing with heavily compressed formats like DVCPRO HD and HDV. There's also the question of edge "enhancement" and other such nonsense done in-camera. But in this case, I would say that 90% of your troubles come from the subject being out of focus. The uneven screen lighting is just going to take you longer to key... At which point, you may find it better to use the key as a starting point and then roto the subject out. May take a bit longer, but in the long run may be less stressful and you'll get better results. I suppose it depends on how much greenscreen footage you have to work with.

Quote:
distance, he was about 15 feet from the wall, we coudnt get further.
15ft should be more than fine. How close is your camera to the subject? I would start by fixing the focus issue.

Quote:
I'm not the only one running into this problem, everyone how uses the studios hvx has the same halo, I'm just really the only one trying to fix it.
Hmmm... The halo issue looks mainly like a focus issue. Perhaps this HVX isn't focusing properly and is due for service?

Get the subject 100% in-focus. Even turn AF on and shoot at 720p60 and see if you get focus issues/halos then. You should get sharp images at 60p with AF on and a properly lit screen and subject. Shot with what should give proper results and then step away from it... 720p60 works? OK, go to 720p24. Works? OK, try 1080p24.

If you can isolate a problem with this HVX, then you can tell them to get it repaired and/or give you another to work with.

When shooting 720p24 and 1080p, I never use the focus assist. It's too slow and unreliable in most cases. I set the focus info to read out by distance and go with that. Autofocus works pretty good if you stick with 1080i and 720p60 modes, if that's the look you're going for.
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Old February 20th, 2007, 03:51 PM   #8
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Hoorah!

Oooooooooo..... Needs a bit of color correction, looks pretty good otherwise.
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Old February 20th, 2007, 03:58 PM   #9
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I would tweak your scene file settings as well... Detail should be + I think... coring on, skin detail on, etc.. I'll have to pull my settings and see what I've been using. I set up a greenscreen scene file and tweaked on it over the course of a couple months and I haven't looked at it recently.

One other thing too... The amount of noise you have in your shot is excessive (once again, the focus is coming into play here too). You need more light and soft light if you can. But these pics I posted were lit completely with halogen shop lights, screen and subjects. We did get some nasty shadows on the screen, but they were far enough out that a garbage matte took care of them.
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Old February 20th, 2007, 05:15 PM   #10
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Jeff,

How far away from the screen were your lights?

I also have a green wall. We used fluorescents, but they have to be very close to get enough light on the screen. Note that it's important to use the same kind - transformer and electronic ballast tubes have slightly different color temps. It's cool that they have a green tint though...
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Old February 20th, 2007, 09:07 PM   #11
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Lights were 10 to 15 feet from the screen. Halogen contractor style lamps, in this case a stand supporting 3 directional lamps, each with a 110W halogen bulb. We used two of these units plus overhead fluorescent lighting within the room. ...Just what we had. It really wasn't enough light and the fluorescents were a real PITA - I hate working in, around or under fluorescent lighting. The halogens lit the screen and subjects an keeping them spaced out from the screen at about a 45 degree angle pointing back at the subjects and the center of the screen. Like I said, it created some shadows, but shadows were to the sides of the subjects and are easy to drop off with a garbage matte in post in a decent app like Shake.

Subjects were about 8 feet from the screen. A little too close in this case, but it was the compormise we had to deal with in order to get the best overall lighting -- given what we had to work with. You can see this as there's a bit of green spill on the girls. Most obvious on the one girl's shorts just to the left of where she's holding the sword.

As for lights having a green tint, that's a bad thing - not cool. :) The last thing you want is a green/yellow tint or spill when you're working with greenscreen. If you're dealing with green tint, lots of yellow subject matter even blonde hair in some cases, I would look toward using bluescreen. Blue also works better sometimes if the subjects are to be comped into night scenes - any spill will be blue and is a lot easier to cope with. I prefer green though if the subjects have a lot of black or dark clothing - in this case the black leather. Green has a lot more luma capacity than blue and it's easier to pull a key from a green background, but sometimes harder to blend/hide the flaws.

For most of my chromakey work I actually use a 10'x24' chromakey cloth backdrop I bought from B&H - about $350. On one side it's green, the other side is blue. I've only had it for about a month now, but it's working really good so far and it's easy to transport and set up with a frame I made from 2.5" PVC pipe and fittings (some glued, some not) that just snap together. Before that, I was doing smaller stuff and just had an 8' high 10' wide greenscreen in my basement I made from a 2x4 and plywood frame. 1/4" smooth-finished drywall painted with about gallon of greenscreen paint.

This project I'm showing here with the girls is in front of a green wall in an old warehouse building. Not my setup, I was running b-camera on a quick-and-dirty shoot for a small short and mock trailer. Trailer is done and submitted to the appropriate festival for consideration, but the short is still being worked on....
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Old February 20th, 2007, 09:59 PM   #12
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i'm not going to be at my shake station for a couple hours but when I am I'll grab your png and break up the layers, to see if you have those peskie lines as well. have you tryed running some keys on it.

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Old February 21st, 2007, 12:12 AM   #13
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that looks really nice, can you uploaded a few more images in sequence so I can test them, I just got a pretty good look, pulling only two keys and a spill sup, its a stil images, so I'd like to see some movement.

correct me if I'm wrong, but did you say you were using the same lights on the screen and subject? this seems pretty risky, how many keys are you finding you have to pull to get a perfect matte?

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Old February 21st, 2007, 12:24 AM   #14
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Quote:
Originally Posted by Jeff Kilgroe
As for lights having a green tint, that's a bad thing - not cool. :) The last thing you want is a green/yellow tint or spill when you're working with greenscreen.
Understood, however, we put the fluorescents right near the wall and did a reasonable job of flagging off any direct light on the talent. Of course, there's still some bounce off the paint, but that will be green regardless of the color temp of the lights.

FWIW, the paint we used was called "Lime". I could check the brand if anybody's interested. We got a bunch of paint chips, shot them under fluorescents with our camera (Panasonic GS500), then checked the waveforms to get the purest green.

Anyway, your point is well taken. When keying on green, avoid green light on the talent/foreground - or, at least, overpower it with the main lights.
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Old February 21st, 2007, 01:15 AM   #15
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I'll see if I can dig up some or even shoot something new with better lighting (possibly this weekend or early next week I might be able to shoot). As for this particular project I really shouldn't post any more of it right now.

Quote:
Originally Posted by Jason Miller
correct me if I'm wrong, but did you say you were using the same lights on the screen and subject? this seems pretty risky, how many keys are you finding you have to pull to get a perfect matte?
You understood correctly. The same lights were lighting both the subjects and the screen. Very risky. Honestly, I'm amazed that it worked at all. But like I said, we used what we had available within the time available. The girls were awesome to work with, and they were practically doing this for free, but time was seriously limited and so were resources.

The picture is actually a poor example of what can be done with the HVX, or maybe it's a great example of what the HVX can do with poor light conditions if proper care is taken to get a good setup.

I haven't had a lot of time to work on keying this footage. But a garbage matte and spill suppression keeps it clean, some of it I've got away with 2 keys, but most of what I've worked with needs 3.

If I have time and resources to set up proper lighting, I still end up with 2 keys. Depending on my subject I may or may not need spill suppression... Glossy/shiny subjects tend to need spill suppression. But I've had quite a bit of greenscreen practice with the HVX since I bought it a year ago. When I first started out with greenscreen work and the HVX, I was fighting lighting and focus issues constantly as well as camera settings and noise. Tons of trial and error and many of my first greenscreen HVX projects I ended up having to roto by hand to get the results the client wanted.
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