Desaturate Lows Render Issues?

Heya everyone. Yet another fun problem with FCP's color correction I've encountered...

I have a film which relies on a lot of dark imagery, which makes for some very picky color correction. My biggest problem is that to change the overall color tone of some shots, I need to mess with the lows in the 3 way color corrector. This often turns what should be my base blacks a bit colorful and brighter. Desaturate lows seems the perfect solution. The problem :

Looks great in the preview render on a broadcast monitor. However, when it is actually rendered it suddenly becomes heavily pixelated.

Any advice on what's going on, or how I can recreate the desaturate lows effect in a fashion that can actually be rendered?

My stats:

10 Bit Video, BlackMagic Decklink Card, Dual G4 Mac (this same problem occured on a G5 too), FCP 5.0.4

An update. I just upgraded to version 5.1.2, and the problem persists. I'm running Mac OSX 10.4.8, too, if that helps.

I'm worried that it might be a freak problem with my setup, because I can't seem to find any instances in my online searches of any problems with this filter.

If nobody has ever heard of this, I'd much appreciate some kind of workaround advice... Is there any trick to desaturating the lows or toning the color of a shot without touching a certain threshold? 3rd party filters?

One simple step to perfecting my color correction... so close, and yet so far! Heeelp!

It's hard to follow what you're actually trying to do. I think what you're saying is that you're raising your blacks to the point that the picture loses contrast and gets washed out. If you're raising them to the point that they've atualky got pixelated colours in them you've gone way too far.

Have you tried leaving your blacks alone and playing with your mids, or working with gamma correction?

What is is that you need to achieve? Brighten the overall picture?

Also, are you watching this on a broadcast monitor or on a computer monitor? What you see after render is the picture prepared for TV. It will not look correct on a computer monitor. Ever.

Jude Cotter Wrote:
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> It's hard to follow what you're actually trying to
> do. I think what you're saying is that you're
> raising your blacks to the point that the picture
> loses contrast and gets washed out. If you're
> raising them to the point that they've atualky got
> pixelated colours in them you've gone way too far.

I'm not raising my blacks at all, so much as colorizing the low tones of the image. The images I'm working with are very dark, so the touching the mid tones often doesn't cover the overall look of the shot. The low tones do. However, the slightest amount of color correction brings color into the "true blacks". Desaturate lows is the perfect solution, which lets me preserve these blacks while adding color to the rest of the image.

> Also, are you watching this on a broadcast monitor
> or on a computer monitor? What you see after
> render is the picture prepared for TV. It will not
> look correct on a computer monitor. Ever.

As I said in my first post, I am watching through a broadcast monitor.

Anyway, it isn't of much consequence now... I just discovered the solution. I scoured my settings and discovered that my sequence was set to Apple uncompressed 10 bit. When I set it to Blackmagic, it could render everything correctly. Not sure if this render bug pops up when I'm not running the decklink... scary, though.

Oh - I didn't realise you were messing with the hue. It sounded like you were trying to raise the luma and were losing contrast.

There's also a plug-in - a freebie somewhere, called .. Black restore - or something like that, that could help. Sounds like you've got it sorted anyway.