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EX-1 green screen

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davetdh
EX-1 green screen
on Jan 3, 2008 at 2:42:08 pm

When I first saw the specs for this camera I thought "yes" here is a HD camera I could live with. I/2 inch sensors, all the frame rates and full HD! But... as I have been reading some of the post about this camera I am concerned about the 4:2:0 color space. I do a fair amount of green screen now with my DSR 500ws dvcam and it is ok. I was really looking to improve my keys. So my question is how do you record off the head and get the 4:2:2? What are you recording to? A laptop running FCP and capture now? I am just starting down this HD road and it's a lot more involved than I thought. Thanks for any input


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Juan Martinez
Re: EX-1 green screen
on Jan 4, 2008 at 9:55:52 pm

Actually, the Ex1 outputs honest to goodness 10-bit 4:2:2 at all resolutions via its built-in HDSDI/ SDI interface.

Now, a word about "color space". In the old SD days, 4:4:4, 4:2:2 and 4:2:0 had absolute meaning and direct correlation to the picture quality (luminance and color resolution). In the case of HD, 4:4:4, 4:2:2 and 4:2:0 are relative. Thus, these ratios have no "real" meaning anymore. Therefore, it would be possible for an HD format with small luminance and color spatial resolution to claim 4:2:2... so, the only way to compare is to count the actual captured pixel resolution. Once, you know the exact number of luminance pixels stored, you can apply the ratio to compare apples to apples (for a given aspect ratio).

For compositing, all that is necessary is for color sampling to be tight enough for the keyer to effectively detect the edges. You will find that Ex captures 960 color pixels in the horizontal direction capturing a higher color resolution than some HD formats. The color sampling is also halved in the vertical to 540, which is still suitable for good keying. Lastly, at the core of modern compositing engines are sophisticated keying algorithms that even look at luminance transitions to more accurately detect the edges. Please try keying with Ex 4:2:0. I believe you will be surprised how good keys you will be able to achieve.

Sorry for the long winded reply. I hope it helps.

Juan Martinez
Senior Manger Technology
Sony Electronics


Juan Martinez


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Saro Varjabedian
Re: EX-1 green screen
on Feb 11, 2008 at 12:29:52 am

Hi Juan,

I recently purchased an EX-1. One of the main reasons I purchased the camera was because of the 1/2 inch chip and the ability to record 10 bit 4:2:2 from the HD/SDI port. Now, I've been reading conflicting information on all the forums and I'd like to confirm that the video being streamed through the HD/SDI port is coming directly off the head and not coming from the computer inside the camera? Can you clarify?

Thank You



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