What could be causing this? - picture included at DVinfo.net

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Sony HVR-V1 / HDR-FX7
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Old July 11th, 2009, 08:47 AM   #1
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What could be causing this? - picture included

Could somebody please shed some light on this for me? The pixelation around the arms of the guy on the left of the pic, is what is concerning me.
This shot was taken at the rehearsal for this play and we start shooting the main event tomorrow night, so any help or advice would be greatly appreciated.

Many thanks
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Antonie Koen is offline   Reply With Quote
Old July 11th, 2009, 10:51 AM   #2
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Hard to tell from a single still frame, but my first though was it could be interlace artifacts... although I only say this because I can see interlacing in other parts of the image.

I went searching and found this thread about http://www.dvinfo.net/conf/sony-hvr-...toin.htmlwhich which offers another possible explanation, but again, it is hard to know from a single still frame.
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Old July 11th, 2009, 11:40 AM   #3
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Yes, hard to tell from a still.

If you are talking about the video noise that is all over the black areas at the left of the frame, this is probably coming from gain being applied because of low light.

This is a common problems in low light when the camera is in automatic. It is likely to occur any time that the gain is over 9db.

It is one of the reasons I shoot in manual as much as possible. Manual control is not the only solution, people who prefer to shoot in automatic will set the AGC limit to 9 or lower, I believe this is found in the Picture menu.

What this will do to your exposure? Hard to know until you try it. What is good lighting for a play may not be good lighting for a camera. Certain cameras have incredible low-light performance, the V1 isn't one of them. The PD150/PD170 are amazing in low light (standard definition).
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Old July 11th, 2009, 12:16 PM   #4
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Unfortunately on the V1 and FX7 you only have a choice of 0, 6 or 12 dB on the AGC limit. This setting is found in the CAMERA SET menu. I always have mine on 12 because I don't mind a little bit of grain in a really dark scene. But you could try 6dB.

We shot our first couple of shows on full manual exposure and found it was a considerable pain and didn't really result in any better exposure than using AUTO in SPOTLIGHT mode. You could also try AE SHIFT at -5 or so.

BTW, reds will always be very problematic with Sonys, as in the scene you posted.
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Old July 11th, 2009, 04:18 PM   #5
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Thanks guys for your responses much appreciated.

Adam, I have found with the V1 under red light I get a kind of blockiness (pixelation) which I am not crazy about, but it doesn't look like there is a way around this (saying this, I haven't checked out John's link yet).

As far as the gain goes, the AGC is set to 12. This play is for my local church and the camera men lack the experience to go manual, so this is the reason for Auto Iris and Auto Gain (with AGC). We did the rehearsal with these settings and I it came out fairly well.
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Old July 12th, 2009, 03:14 AM   #6
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The reds... Maybe some 4:2:0 chroma subsampling issue as was already discussed in http://www.dvinfo.net/conf/sony-hvr-...-hdv-reds.html

Intermediate codecs upsample chroma and may reduce the issue during your editing session, but that's only temporary as it should show up again anyway in the 4:2:0 distribution format (BD, DVD). How studios manage to work around the format limitation and avoid this in commercial DVDs / BDs is still a mystery.

I tried applying Gaussian blur on a chroma layer in After Effects, only results in poor-looking desatured video. Some more ideas, maybe worth trying:
- Use AE to apply blur to the red channel only.
- Use secondary color correction to desaturate the reds until pixellation is less apparent.
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