This IS the Avid L2: Re: [Avid-L2] Illegal levels clip fine with Safe Colors but don't clip UPON RENDER

Monday, February 4, 2013

Re: [Avid-L2] Illegal levels clip fine with Safe Colors but don't clip UPON RENDER

I remember seeing pretty much the same issue with some BCC effect a
couple years ago. I think it was the math composite effect. If the BCC
safe colour limiter was turned on, then the levels looked correct when
unrendered, but wrong when rendered.

The only workaround I found was to colour correct the footage to be
legal before applying the effect. Not much help to you, I'm afraid.

Cheers,
--Michael

On 13-02-04 5:13 PM, Mark Spano wrote:
>
> Hi folks,
>
> Here's a new one for me. Take any clip that has a few bits of information
> below 0mV or above 700mV (luma, R, G, B, whatever). For example, here's an
> external scope view, where everything green is above 0 and everything red
> is below 0:
>
> http://i.imgur.com/rp94vzB.jpg
>
> Knowing that the particular clip in my edit would be fine to crush a
> bit, I
> figure I'm fine with just dropping a Safe Color effect on to clamp at 0.
> Using either the Avid Safe Color Limiter effect, or the Boris Color
> Correction effect with Safe Colors checked, when I drop either one
> onto the
> clip in my timeline, I get the desired result, which looks like this:
>
> http://i.imgur.com/jKh4Cxg.jpg
>
> I've got it set to clamp at 0mV low luma, 700mV high luma, and even 16/235
> for my RGB. It does a PERFECT clamp across all my luma (as you can
> see) and
> RGB channels, which is what I'm looking for.
>
> Now here's where it gets weird. If I render/mixdown/export, it still does
> the clamp, but misses a lot of stuff! In this case, it ends up looking
> just
> like the clip without the effect:
>
> http://i.imgur.com/rp94vzB.jpg
>
> WTF? This happens with stuff going on above 700mV too.
>
> Upon further testing, it appears that any of these effects work flawlessly
> when you drop them in, but when rendered, they miss some stuff. If you
> clamp without rendering, and park on an offending frame, zero alarms will
> go off on the scopes. But as soon as you play/render/export/mixdown, the
> effect goes from being precise to being approximate.
>
> This happens with almost any clip (AMA, native DNxHD, etc.), on every
> system I have (Mac, Symphony 6.0.3.2) and user setting I have (new
> included). I feel like it's better with progressive material than
> interlaced. I wouldn't even mind it so much, but the unrendered effect is
> PERFECT. But what good is that, when it stops being perfect on playback,
> render, export, or mixdown?
>
> I am sufficiently boggled by this. Anyone else see this happening? To be
> clear, I am talking about TINY infractions. But the pre-rendered effect
> gets the outliers - that's the stumper.
>
> [Non-text portions of this message have been removed]
>
>

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