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Old April 24th, 2007, 09:48 AM   #1
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The Magic Changing Blacks

Hey everyone,

I just finished shooting a series of music videos and there was something I noticed about the footage when I got back into the edit suite.

There were times, when shooting in sunlight (towards dusk, maybe at less than a 45 degree angle) when our actress's black top would become a deep maroon or burgundy. This happened several times with clothing and always with black turning into that deep red.

We shot with the Red Rock Micro and captured on P2 cards.

It was only when in sunlight. And it doesn't affect anything else in the the shot, just the blacks in clothing.

Has anyone else had any experience with this?

We also got a lot of green in all our footage which is something I've heard is common with HD.
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Old April 24th, 2007, 10:54 AM   #2
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Sounds like lens flare. Sometimes it is not as obvious as a huge flare in the middle of the picture.

Quote:
Originally Posted by Josh Caldwell
We also got a lot of green in all our footage which is something I've heard is common with HD.
If you have a green color cast, either something is wrong with the lenses or the camera. HD is not predisposed to any color casts, nor is any other format of video. Most likely culprit is bad white balance, followed by old/substandard lenses on the Red Rock.
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Old April 24th, 2007, 11:16 AM   #3
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Sounds like lens flare. Sometimes it is not as obvious as a huge flare in the middle of the picture.
The camera lens isn't pointed towards the sun. It's always pointed away from it.



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If you have a green color cast, either something is wrong with the lenses or the camera. HD is not predisposed to any color casts, nor is any other format of video. Most likely culprit is bad white balance, followed by old/substandard lenses on the Red Rock.
In the recent issue of American Cinemtographer Harris Savides, who DP'd Zodiac, mentions they had to use a Lee 20 CC magenta filter to compensate for the green bias of the RAW files on the Viper.

This might not apply to us with the HVX, but there is a slight predisposition to green in raw HD footage. So, I didn't know if that was common or not.
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Old April 24th, 2007, 11:24 AM   #4
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You need to record some bars from the camera and then view footage on a properly calibrated monitor. When people complain of color cast on footage it is usually the monitors fault. As Nate said: Proper white balance on a proper white card, continue pressing the WB button and the camera will also do a Black Balance. And we usually shoot a test chart as well. The HVX can be phase balanced, but you need to know where you are at and where you are going.
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Old April 24th, 2007, 03:56 PM   #5
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On a recent outdoor, bright sun shoot (HVX, Brevis, Nikon lenses), I noticed the slate person's black shirt looked almost purple. I tried adjusting the white balance and scene file, but couldn't resolve it. It might've been the cheapo 4x4 filters (Cavision). It didn't matter though... the talent wasn't wearing black and I could've just fixed it in post if I needed to. It was weird though.
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Old April 24th, 2007, 05:20 PM   #6
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This could have something to do with the dye used to make the fabric look black. Some "black" dyes are very very dark purple, some very very dark blue -- I have vivid memories of this from chem lab years ago in which we created such dyes. Black inks are much the same.

Under very intense sun you might be able to seen the purple cast in fabric.
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Old April 24th, 2007, 05:31 PM   #7
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Quote:
Originally Posted by Josh Caldwell View Post
The camera lens isn't pointed towards the sun. It's always pointed away from it.
Then I'd look for a light leak on the back of the Red rock where it interfaces with the HVX lens.

Quote:
Originally Posted by Josh Caldwell View Post
In the recent issue of American Cinemtographer Harris Savides, who DP'd Zodiac, mentions they had to use a Lee 20 CC magenta filter to compensate for the green bias of the RAW files on the Viper.

This might not apply to us with the HVX, but there is a slight predisposition to green in raw HD footage. So, I didn't know if that was common or not.
The Viper is only one of many HD cameras. It's not a trait of HD in general.

To go one step farther, specifically with the Viper, it's a trait of the RAW matrix in the Viper. It has nothing to do with the format (HD).
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Old April 24th, 2007, 05:43 PM   #8
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Looks like we might all be wrong:

Take a look at: http://diglloyd.com/diglloyd/free/In...amination.html

The infrared reflectance would explain why it's only in the sunlight one sees the problem.
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Old April 24th, 2007, 07:49 PM   #9
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I'd agree. This sounds more likely than flare. If the problem is intermittant, then maybe flare. If it's consistent and stable, I'd look at this.

The green part is Viper only though. None of the cameras out there have noticible color casts as a rule.
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Old April 24th, 2007, 11:17 PM   #10
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Good to know. Looks like this might explain the problem. Quite interesting, huh?
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Old April 25th, 2007, 02:38 AM   #11
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Quote:
Originally Posted by Peter Wiley View Post
Looks like we might all be wrong:

Take a look at: http://diglloyd.com/diglloyd/free/In...amination.html

The infrared reflectance would explain why it's only in the sunlight one sees the problem.
That's definitely the explanation I was thinking of.
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