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footage too yellowish


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#1 Ruby Gold

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Posted 27 July 2007 - 03:16 PM

I shot an interview with my DVX100b yesterday, using 3-point lighting and manually white balanced the camera. White balance was achieved, though the "ND 1/8" indicator flashed at the same time, for a second, and I'm not sure what that meant. I set my zebras at 85% (my subject was African-American) and set the exposure manually so that the zebras were just barely visible on her highlights (about 5.6). In the LCD it looked great.

Now that I'm looking at the captured footage, it looks slightly yellow and her highlights look too hot. Given that the zebras weren't really visible, hardly, and the manual white balance was achieved, I'm not sure why it's too yellow and the highlights too hot.

I want to correct this before the next interview, so all help greatly appreciated--particularly around why the ND 1/8 indicator came on and what I might have done wrong. Thanks!
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#2 Michael Nash

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Posted 27 July 2007 - 04:19 PM

The ND indicator probably came on during white balancing because your white card was probably too far overexposed. The camera may have set a white balance, but if any of the color channels were clipped (over 100%) the balance may not have been accurate.

85% is pretty darned bright for African-American skin! For Caucasian skin I rarely let the highlights go above 80%, so you were probably overexposing.

Exposing by the camera's onboard LCD is tricky. You have to make sure that the LCD brightness, contrast, and color saturation are set up correctly, and you have to make sure that you're viewing it from the proper angle (pretty much straight-on), and away from too much stray light. Viewing angle is critical for exposure; if it's tilted too high the image looks brighter than it actually is, tilted down too much and the image looks darker. And even when viewed straight-on in optimum conditions, the blacks and deep shadows will look brighter on the LCD than they will on a CRT. Oh, and the color on the DVX's LCD isn't really accurate either. Some hues come out different, and the color temperature can be off a little bit.

The easiest way to make sure the LCD is set up correctly is to view the same image on the LCD and another properly calibrated monitor; preferably a CRT. Adjust the LCD's settings until the image closely matches what you see on the other monitor. Shoot some test footage, review, and repeat as necessary.
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#3 Ruby Gold

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Posted 28 July 2007 - 07:05 PM

Thanks so much for this incredibly thoughtful response--really helpful.

I'm thinking your first comment about the ND warning indicating white card overexposure and therefore setting the WB incorrectly because the color channels were clipped is likely what happened. If this were the case, in the future wd the better thing to do be to close the iris down enough for the ND warning does not appear, and then white balance? Do you think that wd correct it?

All your points about the LCD are well taken and I get it--sadly I don't have a monitor, and, until now relying on the zebras has worked for me. I was surprised by your comment about 85% being too bright for AA skin. I usually set them at 80% for Caucasian skin and 85% for dark skin. Am I going in the wrong direction? I thought that a higher percentage (e.g. 85 vs. 80) wd allow more brightness in order to accurately assess exposure for darker skin. Not so? What wd you typically set zebras at for Caucasian and AA skin on a DVX100b?

Thanks again for your help and I hope you don't mind the additional questions.
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#4 Robert Hughes

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Posted 28 July 2007 - 08:37 PM

Heck, I see your problem - it's your posting name. Change it to "Verde Green" or "Violet Brown" and your yellow tinting problems will disappear. :lol:
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#5 Ruby Gold

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Posted 28 July 2007 - 08:56 PM

Now why didn't I think of that?? <_<

and, yes, it's my real name...
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#6 Michael Nash

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Posted 29 July 2007 - 11:57 PM

in the future wd the better thing to do be to close the iris down enough for the ND warning does not appear, and then white balance?

I was surprised by your comment about 85% being too bright for AA skin. I usually set them at 80% for Caucasian skin and 85% for dark skin. Am I going in the wrong direction?


You'll get the most accurate white balance results when your white card is close to "white" -- that is, not clipping, and not so dark that it's middle gray. As long as your white reference is generally between 70-90%, you should be fine. So yes, you do need to consider the exposure of your white card when white balancing.

African American skin is obviously darker than Caucasian, so you'd expect that the brightest parts of the face would be darker (less than 80%) at a "normal" exposure. So if you were to expose the highlights at 80%, the exposure would already be brighter than it would with Caucasian skin. By using 85% as a reference for AA skin, you've made it even brighter than that!

An "accurate" exposure of African American skin would be the exact same as would be for Caucasian skin -- like if a Caucasian person and an African American sitting right next to each other in the same lighting. If lit evenly, a "normal" exposure on the DVX should handle both skin tones just fine. When you open up the iris for more exposure on the darker skin it's actually less accurate, although it might give you better skin color and detail. But using a brighter exposure reference for darker skin makes it even less accurate.

I use 70% zebras period, unless using a camera like the DVX that only goes down to 80. For African American skin I just wouldn't expect any of the skin to give zebras, except for maybe some small "shiny" highlights. I just make sure my LCD (working monitor) is set up/viewed correctly, and expose by eye. Remember, it's usually better to err on the side of underexposure with video, rather than over.
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#7 Daniel Sheehy

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Posted 07 August 2007 - 12:58 AM

If you have doubts about the exposure, don't forget that you can switch the zebra's up to 100 or even 110 and check for clipping.

Then you have no reason to get a nasty surprise later on. ;)
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#8 Michael Nash

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Posted 07 August 2007 - 02:55 AM

If you have doubts about the exposure, don't forget that you can switch the zebra's up to 100 or even 110 and check for clipping.

Then you have no reason to get a nasty surprise later on. ;)


But 100% zebras won't tell you if you're overexposing skintones, pushing the highlights up higher than 80% where you can get color shifts and artificial looking saturation. That's what 70% zebras are for.
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#9 Daniel Sheehy

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Posted 13 August 2007 - 10:38 PM

But 100% zebras won't tell you if you're overexposing skintones, pushing the highlights up higher than 80% where you can get color shifts and artificial looking saturation. That's what 70% zebras are for.


Absolutely correct, my comment was about exposure and highlights in general.
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