lighting problems,

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lighting problems,

Post  jiraiya on Mon Dec 08, 2008 12:56 pm

i've got 2 halogen worklights to light up a chromakey backdrop. when watching the video back the green is realy whitened out and causes overspill on the subject. what is the idea length away from the chromakey back drop and also be able to keep the screen green and well lit and also make the subject seperate from the backdrop?

if anyone can help me out of sugest a few tips for keeping the green vivid and not cause total white out.

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Re: lighting problems,

Post  tr3885 on Mon Dec 08, 2008 5:14 pm

jiraiya,

I've been working on the Chroma Key as well. Some tips, you should be more than 4-5 feet in front of you screen. Your screen lights should be where they can wash over the green screen. As you said, that the green is whitened out, you need to filter your light such as a fiberglass mat to diffuse the light. Also, it helps a lot to have a 3 point light set up to light your subject. Again, filter your light as not cast dark shadows on your green screen. The closer you can get the camera to you, the better. Lower end camera have a hard time "seeing" defined edges of the subject vs. the background.


The best tip that I can give you on this is to get the DVD's from Mark Apsolon. Mark and I have had a lengthy conversation on this exact problem that I have been having. My problem is minimized with the Mark's help until I can get a better camera. With what I have worked on with my camera, I can now at least do some web production video's.

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Mark's YouTube Videos on Chroma Key Lighting

Post  NewEnglandMultimedia on Mon Jan 19, 2009 11:47 pm

Hello Mark,

First, I would like to thank you for sharing your knowledge and experience with us through useful and practical video tutorials.

I was thinking about getting your DVD to help me with my chroma key/lighting issue, but I'm hoping you can assist me in the meantime.

Here is my problem:

1. I have 1000 watt lights (2 - 500 watt per side) to light the green screen (positioned exactly the way they are in your video).
2. I have a 600 watt ARRI light with a soft box attached (for the light on my "subject" which is me right now).
3. I have a Sony EX-3 HDCAM

As I experiment with different lighting configurations and settings, no matter what I do, I still have a "glow" around me. I have tried rolling off the IRIS, changing the green screen lights to their middle position (250 watts per light) and even tried turning off two of the lights (to prevent the green screen from looking over-saturated (and causing me to roll off the IRIS setting on the EX-3.

I suppose my initial questions for you are:

1. The chroma key work on the videos - was that done with your exact configuration you showed in the video or were there some tweaks done that are not in the YouTube video?
2. Does your DVD cover lighting in great detail?
3. What chroma key software did you use in creating your videos?

I have watched a lot of tutorials and I seem to be doing everything right - but my results are not as good as yours are. Truthfully, nobody else's that I've seen on YouTube are.

Do you have any suggestions for me (based on the limited information I'm sharing here)?

Thank you again Mark for all your doing to help!

Scott

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Re: lighting problems,

Post  GottaLaunch on Tue Jan 20, 2009 3:23 am

Hi there,

Mark normally uses Sony Vegas to edit his vids,

And since you've some awesome equipment, I personally presume the problem lies with the keying.


Please tell us what software you use for keying, so I can may help you.


Yours, WVD

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Re: lighting problems,

Post  NewEnglandMultimedia on Tue Jan 20, 2009 1:10 pm

Hi WVD -

Thanks for offering to assist me with my green screen and keying problems with the Sony EX-3 (using Sony Vegas Pro 8 for keying and editing).

I realized this morning that I upgraded my XDCAM EX Clip Browser software to version 2 a couple days ago and was exporting the files captured from my EX 3 to AVI instead of the previous MXF format that was the only available option in version 1 of the Clip Browser software. I changed the export format to MXF and my results were much better - but still not good enough (and far from Mark's quality).

I decided to call Sony and I'd like to share the solution given to me in case others might be getting the same poor results.

"The color signal on the various formats - if you have an RGB signal, that would be considered a "4-4-4" sample. So for every 4 samples of red, there are 4 samples of green and 4 samples of blue (horizontally and vertically). In the higher-end products, where you would have component recordings, then you would have a 4-2-2 sampling (black and while sampled 4 times, the color signals would be sampled 2 times (vertically) and 2 times (horizontally). On the EX format (and other formats), it's sampled with a "4-2-0" sampling (the luminous sampled 4 times for every 2 times on the chroma (but the chroma is only sampled vertically - not sampled horizontally).

With 4-4-4, you have full color, with 4-2-2 you have half the color of the 4-4-4, and the 4-2-0 you have half of the 4-2-2. The "jagged" edges I'm seeing are due to the EX not sampling enough color information as it records to the cards.

The solution - to purchase a capture card and go from the SDI Output of the EX-3 to the capture card and capture my video directly to the computer. That way, I get at least a 4-2-2 signal into the computer. You can't get a full RGB signal out of the EX-3 but I can get a 4-2-2."


They recommended purchasing an AJA capture card.

So it looks like after all my setup, getting the green screen (from Tube Tape) and spending hours and hours troubleshooting, I need to buy something! Isn't that the way it always goes?

QUESTION: What camera was Mark using on the DVD training videos? Also, was he using a capture card??

I hope this post helps other save some time if they are running into the same green screen and keying problems I've had this week.

Thank you!

Scott

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Re: lighting problems,

Post  NewEnglandMultimedia on Tue Jan 27, 2009 11:25 am

Mark,

Can you add anything to this post?

Thanks,

Scott

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Re: lighting problems,

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