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Sony HVR-A1 and HDR-HC Series
Sony's latest single-CMOS additions to their HDV camcorder line.


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Old December 22nd, 2008, 06:49 PM   #1
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Sony HDR-HC3 light halo around subject on green screen

Hi,

I have set the camera's sharpening to the lowest setting. Unfortunately there is still a light green halo around the subject I'm shooting in front of a green screen.

I'm connecting the video directly out of the HDMI output of the camera into a BlackMagic Intensity card on my Mac Pro.

Would this camera still be performing some level of sharpening even on the lowest setting? Or am I getting the halo because I am lighting the green screen too brightly compared to the subject?

Have attached a sample screen shot zoomed in to show the light halo.

Any tips would be appreciated.

Tony
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Sony HDR-HC3 light halo around subject on green screen-hc3greenscreensample.png  
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Old December 22nd, 2008, 08:43 PM   #2
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How close is the subject to the green screen?
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Old December 22nd, 2008, 11:20 PM   #3
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I believe John is on the right track. More than likely there is not enough separation between subject and backdrop. What is actually happening is the lighting from or for the screen is so bright its illuminating off and onto the back of your subject.

Separate the two with a greater distance
or
Use more diffusion to soften your light sources
or
Both
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Old December 23rd, 2008, 12:39 AM   #4
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Hi,

The subject is at least 2.5 metres away from the screen. This is all I can afford in the confined space we are in.

I'm using two Lowel Tota lights (Lowel Tota-light) to light the screen.

Perhaps I should use a couple of umbrellas on these to diffuse the light. I have also tried to use a Lowel Pro Light (Lowel Pro-light) to light the subject from behind with an umbrella (white) but perhaps that has diffused the light too much.

So you don't think its the camera sharpening? I was think I should buy a Canon HV30 given I have heard so much good reviews relating to it being used for green screen work.

But if its not sharpening, and its lighting, I'll do my best to work on that.

Tony
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Old December 23rd, 2008, 12:55 AM   #5
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It all factors in.

You can also use a scrim to help diffuse the light as well. This episode here also will help you, http://cdn2.libsyn.com/idlemindspodc...f5de5dd63abbf0
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Old December 23rd, 2008, 01:12 PM   #6
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There also is one more possibility: Your camera color encoding maybe the culprit. Is the halo just on one side of the subject or on both? Is it appearing and disappearing as you move the camera or as the subject moves? I can’t tell from your picture, because it may have been re-sized to show the detail, but is the halo just one pixel wide in the original? If you say yes to any of these questions, then in my opinion it is the 4:x:x color encoding, you are using consumer camera to do a professional effect.

In the attachment is a test I did (few years ago) in my NLE (4:2:2 processing), where I had a single pixel line on a white, red, green and blue backgrounds. The top is the original and the bottom is the 4:2:2 encoded output. Notice the one pixel distortion in all lines with color background (not in white). This is due to the fact that there are two luma samples for each color sample. In other words, if the luma changes within chroma sample, you will get this ‘shadow’, ‘halo’ effect. A horizontal shadow is true in 4:2:2 encoded signals, but you also have it vertically. To me, it indicates your signal is less then 4:2:2, meaning that one color sample takes care or two pixels horizontally and two pixels vertically: maybe 4:1:0?
If in fact this is the culprit, then this is not the camera for the green screen work, you need a better camera.
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Old December 23rd, 2008, 04:24 PM   #7
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> Would this camera still be performing some level of sharpening even on the lowest setting?

That gets my vote. I agree with Robert's point, but in this case the halo looks to be more than a single pixel in width, and looks an awful lot like sharpening.
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Old December 23rd, 2008, 07:26 PM   #8
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It's probably worth a mention that while the sensor size of the HC3 is about the same as later cameras, it had a lower overall resolution (fewer pixels in about the same dimensions) than either it's predecessor (HC1) or the majority of subsequent cams (except the HC5 that shared sensors with the HC3 IIRC).

That might account for some of the problems? It may well be the HC3 is not quite up to the task - great little camera, but IQ/PQ left a bit to be desired when compared to later cameras.
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