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Black Level and Zebra Pattern (Please exercise patience)


Robert Goodrich

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I'll confess that this stuff still blows my mind. right now I own an XL1s (getting an XL2), and I've always left those settings alone, 1) 'cause you can't adjust the setup between 7.5 and 0 on an XL1s, and I leave things alone that I don't understand and 2) 'cause it looks better to not lower the setup (crushing blacks on the XL1s tends to orange up the skin tones in an unattractive away). I've always left it at 0. So 0 bad, 7.5 good?

 

 

I seem to recall that on the Canon XL1S there is a memory setting in which you can raise the set-up level if you desire and keep it instantly available (also for chroma level and hue, and perhaps sharpness as well).. Frankly, I'm a fan of black stretch on the lower end of the I.R.E. scale but I'm not sure how set-up intertwines with black stretch on an XL1S.

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Yes, there are the custom presets where you can adjust setup. What I mean is, there's no "7.5" selection in the menus, the adjust ment is made with a little slider bar, and you can move it (I think) 6 notches down, or 6 notches up. What those adjustments mean is anyone's guess. Like I said, it looks "wrong" to adjust it, to my eye. I played with it once, in a low key scene, and noticed that while, yes, it was deepening the contrast/crushing the blacks, it was also making my caucasian actor's scene unpleasantly/reddish orange compared to the default setup level. It's not a very fine adjustment, is what I mean. It pulls down way more than the blacks when you mess with it. Beware.

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Yes, there are the custom presets where you can adjust setup. What I mean is, there's no "7.5" selection in the menus, the adjust ment is made with a little slider bar, and you can move it (I think) 6 notches down, or 6 notches up. What those adjustments mean is anyone's guess. Like I said, it looks "wrong" to adjust it, to my eye. I played with it once, in a low key scene, and noticed that while, yes, it was deepening the contrast/crushing the blacks, it was also making my caucasian actor's scene unpleasantly/reddish orange compared to the default setup level. It's not a very fine adjustment, is what I mean. It pulls down way more than the blacks when you mess with it. Beware.

 

The whole idea is to be able to maintain a consistent black level from camera through post and out to final release, without it getting foggy or crushed somewhere along the way.

 

So whatever level black may be set at in camera, you just need to make sure that black is at the proper IRE value when it goes into your NLE. For digital desktop systems that's usually "0," and you can see it on your waveform during import.

 

Increasing contrast also increases the appearance of color saturation. Especially in the case of video, where the camera tends to hold more color in the lower luminances. So yes, when you lower the black level, color in the mid-to-lower luminances will start to look a little rich. The opposite is also true; when you raise the gamma in particular, color will start to look more pastel. Bear in mind that actual chroma saturation is the same; what you're seeing is the combination of luminance and chroma.

 

FWIW, if you're planning on doing color correction it's generally better to start with more color saturation in camera rather than less (up to a point, of course). It's hard too pump up a weak chroma signal without it starting to look fake or "painted-on." But this is all relative to the compression and exactly how much chroma we're talking about. I'm not suggesting you have to over-saturate in camera, just don't reduce the chroma if you're planning on color correcting in post.

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